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Topological investigations of binary mixtures containing ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate and pyridine or isomeric picolines
J. Chem. Thermodynamics 56 (2013) 123–135
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Topological investigations of binary mixtures containing ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate and pyridine or isomeric picolines Subhash Solanki, Neeti Hooda, V.K. Sharma ⇑ Department of chemistry, M.D. University, Rohtak 124001, India
a r t i c l e
i n f o
Article history: Received 9 March 2012 Received in revised form 29 June 2012 Accepted 2 July 2012 Available online 21 July 2012 Keywords: Excess molar volumes, VE Excess molar enthalpies, HE Excess isentropic compressibilities, jES Connectivity parameter of third degree of a molecule, 3n Interaction parameter, v
a b s t r a c t The densities, q, speeds of sound, u of {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + pyridine or a- or b- or c-picoline (j)} at T/K = (293.15, 298.15, 303.15, and 308.15) and excess molar enthalpies, HE of the same set of mixtures at T/K = (298.15) have been measured over entire mole fraction range using DSA-5000 and 2-drop microcalorimeter. Excess molar volumes, VE and excess isentropic compressibilities, jES values have been predicted by utilizing the measured densities and speeds of sound data. It has been observed that VE, HE, and jES values for the studied mixtures are negative over entire composition. The connectivity parameter of third degree of a molecule, 3n (which in turn depends upon its topology) have been applied to predict (i) state of components of ionic liquid mixtures in their pure and mixed state; (ii) nature and extent of interactions existing in mixtures; and (iii) VE, HE, and jES values. The analysis of VE data in terms of Graph theory (which deals with topology of a molecule) suggest that while 1ethyl-3-methylimidazolium tetrafluoroborate is characterised by electrostatic forces of attraction and exist as monomer; a- or b- or c-picoline exist as associated molecular entities. Further, (i + j) mixtures are characterized by interactions between nitrogen and florine atoms of 1-ethyl-3-methylimidazolium tetrafluoroborate with nitrogen and carbon atoms of pyridine or isomeric picolines to form 1:1 molecular complex. The IR studies also support to this view point. The VE, HE, and jES values predicted by Graph theory compare well with experimental values. Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction Ionic liquids are known to be environmentally benign solvents. These are organic salts composed of cations, anions and are liquids at or near room temperature. In the past decade these liquids have emerged as replacement for traditionally used volatile organic salts as they possess physical and chemical properties like negligible vapour pressure, low melting point, a wide liquid range, high thermal solubility, high electro conductivity, etc. They have also been used as reaction media, separation solvent, novel electrolytes, and catalyst in synthesis [1–3]. The vast majority of work published on physical properties of ionic liquid mixtures relates to the systems based on N-alkylpyridinium and 1-alkyl-3-methylimidazolium cations with chloroaluminate (III) ions. The chloroaluminate ions proved to be unstable in air and the problem was overcome by making use of alternative Cl, Br, BF 4 , PF6 , etc. anions. Despite their importance and interest, thermodynamic data on ionic liquid mixtures reported in literature are limited [4–7] which in turn restrict their applications. 1-Ethyl-3-methylimidazolium tetrafluoroborate is one of the latest investigated ionic liquid and ⇑ Corresponding author. Tel.: +91 9729071881. E-mail addresses: [email protected], [email protected] (V.K. Sharma). 0021-9614/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jct.2012.07.007
thermodynamic data of mixtures relating to this ionic liquid is scarce [8–11]. In recent studies [12–15] Graph theory has been employed successfully to predict excess molar volumes, VE, excess molar enthalpies, HE, excess isentropic compressibilities, jES and excess Gibb’s free energy, GE data of the various binary as well as ternary mixtures comprising of organic solvents. It would be of interest to see how Graph theory describes the VE, HE, and jES values of the investigated binary ionic liquid mixtures. These considerations prompted us to measure densities, speeds of sound and excess molar enthalpies data of {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + pyridine or a- or b- or c-picoline (j)} binary mixtures.
2. Experimental section 1-Ethyl-3-methylimidazolium tetrafluoroborate [emim][BF4] (Fluka, 0.98 GC) was used without further purification. The content of water in ionic liquid was regularly checked using Karl Fischer titration [16] and the content of water was less than 340 ppm. Pyridine (Py) (Fluka, 0.99 GC), a-picoline (Fluka, 0.98 GC), b-picoline (Fluka, 0.99 GC) and c-picoline (Fluka, 0.99 GC) were purified by standard methods [17]. The purities of the purified liquids were checked by measuring their densities and speeds of sound values.
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The values for the purified liquids at T/K = (298.15 ± 0.01) are recorded in table 1 and compare well with their literature values [9–11,13,17–21]. Densities, q and speeds of sound, u values of the pure liquids and their binary mixtures were measured using a commercial density and sound analyzer apparatus (Anton Paar DSA 5000) in the manner as described elsewhere [22,23]. The calibration of the apparatus was carried out with double distilled deionised water. The mole fraction of each mixture was obtained with uncertainty of 1 104 from the measured apparent masses of the components. All the measurements were performed on an electric balance. The density and speed of sound can be measured to ±103 kg m3 and 102 m s1 respectively. However, uncertainties in the density and speed of sound measurements are 2 103 kg m3 and 101 m s1 respectively. The uncertainty in VE values predicted from density results is 0.1%. Further, uncertainty in the temperature measurement is ±0.01 K. Excess molar enthalpies, HE for the studied mixtures were measured by a 2-drop calorimeter (model, 4600) supplied by the Calorimeter Sciences Corporation (CSC), USA at T/K = (298.15) in a manner described elsewhere [24]. The uncertainties in the measured HE values are 1%.
jES ¼ jS jidS :
The j values were obtained in the manner suggested by Benson and Kiyohara [25]
id S
j
j j X X T v i a2i T ¼ /i jS;i þ xi v i C p;i i¼i i¼i
i¼i /i
P
ai
2
j i¼i xi C p;i
;
ð4Þ
X E ðX ¼ V or H or ð0Þ
jS Þ
þ X ð1Þ ð2xi 1Þ þ X ð2Þ ð2xj 1Þ2 ;
ð5Þ
ðnÞ
The densities, q, excess molar enthalpies, HE at T/K = (298.15) and speeds of sound, u, data of {[emim][BF4] (i) + Py or a-, b-, or c-picoline (j)} mixtures measured as a function of composition at T/K = (293.15, 298.15, 303.15, and 308.15) are recorded in tables 2 and 3. Excess molar volumes, VE and excess isentropic compressibilities, jES for the various (i + j) mixtures were determined from their measured densities and speeds of sound data using j j X X VE ¼ xi Mi ðqÞ1 xi M i ðqi Þ1 ; i¼i
! Pj
where /i is the volume fraction of component (i) in the mixed state jS;i , v i , ai , and C p;i are isentropic compressibility, molar volume, thermal expansion coefficient, and molar heat capacity respectively of the pure component (i). The C p for liquids were taken from literature [14,26] and a values for [emim][BF4] as well as liquids were predicted by employing presented experimental data [27]. Such jES values for the investigated mixtures are recorded in table 2. The VE, HE, and jES values for the studied (i + j) mixtures are plotted in figures 1 to 9. The VE, HE, and jES data of the investigated mixtures were fitted to Redlich–Kister equation [28]:
¼ xi xj ½X 3. Results
ð3Þ
id S
ð1Þ
i¼i
jS ¼ ðqu2 Þ1 ;
ð2Þ
where xi , Mi, and qi are the mole fraction, molar mass and density of component (i). Excess isentropic compressibilities, jES for the various (i + j) mixtures were determined using
where X ðn ¼ 0—2Þ, etc. are the parameters characteristic of (i + j) mixtures. These parameters were determined by fitting XE (X = V or H or jS ) data to equation (5) using least-squares optimization. Such parameters along with standard deviations, r (XE) (X = V or H or jS ) defined by
rðX E ÞðX ¼ V or H or jS Þ ¼
X 0:5 2 ðm nÞ ; X Eexptl X Ecalc:equationð4Þ
ð6Þ
where m is the number of data points, n is the number of adjustable parameters in equation (6) are listed in tables 2 and 3. 4. Discussion We are unaware of any VE, HE, and jES data for the investigated mixtures with which to compare our results. The measured VE, HE,
TABLE 1 Comparison of densities, q and speeds of sound, u data of pure liquids with their literature values at T/K = (293.15, 298.15, 303.15, 308.15). Liquids
1-Ethyl-3-methylimidazolium tetrafluoroborate
Pyridine
a-picoline
b-picoline
c-picoline
Temperature/K
q/(kg m3)
u/(m s1)
(Expt.)
(Lit.)
(Expt.)
293.15 298.15
1283.89 1279.91
1631.1 1619.4
303.15
1276.26
308.15
1272.07
1284.3 [9] 1279.6 [10] 1280.07 [11] 1276.5 [9] 1275.7 [10] 1271.9 [10] 1272.48 [11]
293.15 298.15 303.15 308.15 293.15 298.15 303.15 308.15 293.15 298.15 303.15 308.15 293.15 298.15 303.15 308.15
983.191 978.249 973.224 968.166 944.401 939.802 935.117 930.414 956.581 952.002 947.449 942.831 955.099 950.179 945.413 940.821
978.24 [17]
939.81 [17]
951.97 [17]
950.20 [13]
(Lit.)
1607.6 1596.3 1442.0 1417.8 1398.0 1377.1 1400.5 1380.1 1361.0 1339.9 1445.9 1424.0 1404.1 1384.0 1451.1 1431.5 1410.7 1389.9
1436.77 [18] 1418.0 [19] 1397.02 [18]
1379.18 [20]
1423.08 [21]
1431.89 [19]
The uncertainty in temperature is 0.01 K; The uncertainty in density value ±103 kg m3; The uncertainty in speed of sound value is 101 m s1; atmospheric pressure.
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TABLE 2 Measured densities, q; excess molar volumes, VE; speeds of sound, u; isentropic compressibilities, jS ; and excess isentropic compressibilities, jES data for the various (i + j) mixtures as a function of mole fraction, xi, of component (i) at T/K = (293.15, 298.15, 303.15, and 308.15). Also included are the various X(n) (n = 0–2) parameters along with standard deviations r(XE) (X = V or jS ).
qmix/(kg m3)
xi
VE/(cm3 mol1)
u/(m s1)
jS /TPa1
jES /TPa1
427.9 406.7 388.8 376.9 366.6 356.0 346.7 339.2 332.2 326.0 320.6 315.3 310.6 306.2 302.6 298.8 296.2 295.5
37.2 47.4 54.2 57.5 59.4 60.2 59.4 57.2 54.6 50.6 46.6 41.9 36.7 31.0 25.1 18.3 11.9 10.1
1466.6 1486.7 1505.5 1517.7 1528.8 1541.1 1550.9 1560.4 1568.3 1575.5 1582.6 1589.2 1595.2 1601.3 1607.0 1612.2 1616.0 1616.8
441.1 418.2 398.5 386.0 375.2 364.0 354.6 346.3 339.3 333.0 327.2 321.9 317.1 312.5 308.5 304.5 301.5 300.9
41.6 52.8 60.6 63.9 65.6 66.3 64.9 62.7 59.4 54.9 50.5 45.1 39.2 33.1 27.0 19.4 12.8 10.8
1450.1 1470.9 1489.4 1502.2 1513.9 1525.0 1536.1 1544.6 1552.8 1561.4 1568.1 1575.5 1583.1 1589.7 1595.8 1602.0 1605.5 1606.2
453.2 429.0 408.8 395.5 384.0 372.9 362.7 354.6 347.2 340.0 334.2 328.4 322.9 317.9 313.6 309.2 306.3 305.6
45.3 57.2 64.7 68.2 70.2 70.1 68.9 66.0 62.5 58.2 53.2 47.8 42.1 35.6 29.2 21.5 14.1 12.0
1431.6 1453.6 1473.3 1487.6 1499.2
467.0 441.0 419.3 404.8 393.1
48.7 61.6 69.8 74.0 75.6
1-Ethyl-3-methylimidazolium tetrafluoroborate (i) + pyridine (j) T/K = 293.15 0.1225 1057.86 0.940 1486.4 0.1781 1085.74 1.225 1504.8 0.2349 1111.05 1.440 1521.5 0.2787 1128.56 1.550 1533.4 0.3215 1144.24 1.622 1543.9 0.3716 1160.99 1.666 1555.6 0.4229 1176.47 1.663 1565.7 0.4723 1189.98 1.620 1574.0 0.5213 1202.28 1.552 1582.4 0.5731 1214.14 1.447 1589.6 0.6212 1224.23 1.324 1596.3 0.6719 1234.08 1.178 1603.2 0.7224 1243.17 1.015 1609.3 0.7737 1251.76 0.839 1615.2 0.8219 1259.31 0.664 1619.9 0.8764 1267.33 0.461 1625.1 0.9223 1273.71 0.287 1628.2 0.9349 1275.41 0.240 1628.9 V(0) = 6.341; V(1) = 2.988; V(2) = 0.274; r(VE) = 0.001 cm3 mol1 ð1Þ ð2Þ 1 E jð0Þ S = 223.3; jS = 117.4; jS = 58.8; r(jS ) = 0.1 TPa
T/K = 298.15 0.1225 0.1781 0.2349 0.2787 0.3215 0.3716 0.4229 0.4723 0.5213 0.5731 0.6212 0.6719 0.7224 0.7737 0.8219 0.8764 0.9223 0.9349 V(0) = -6.511; V(1) = 3.305;
1053.89 1.022 1081.91 1.317 1107.24 1.532 1124.75 1.640 1140.37 1.704 1156.91 1.725 1172.38 1.717 1185.87 1.667 1198.15 1.592 1209.97 1.478 1220.11 1.354 1230.00 1.206 1239.16 1.045 1247.81 0.869 1255.42 0.695 1263.49 0.491 1269.86 0.312 1271.55 0.262 V(2) = -0.889; r(VE) = 0.002 cm3 mol1
ð1Þ ð2Þ 1 E jð0Þ S = 243.3; jS = 137.8; jS = 71.0; r(jS ) = 0.1 TPa
T/K = 303.15 0.1225 1049.31 1.055 0.1781 1077.49 1.359 0.2349 1102.93 1.576 0.2787 1120.49 1.685 0.3215 1136.25 1.756 0.3716 1152.96 1.786 0.4229 1168.48 1.777 0.4723 1182.12 1.735 0.5213 1194.47 1.660 0.5731 1206.44 1.553 0.6212 1216.67 1.433 0.6719 1226.63 1.285 0.7224 1235.85 1.124 0.7737 1244.54 0.945 0.8219 1252.16 0.767 0.8764 1260.17 0.548 0.9223 1266.47 0.355 0.9349 1268.13 0.299 V(0) = 6.776; V(1) = 3.138; V(2) = 1.153; r(VE) = 0.002 cm3 mol1 ð1Þ ð2Þ 1 E jð0Þ S = 257.0; jS = 147.4; jS = 91.2; r(jS ) = 0.1 TPa
T/K = 308.15 0.1225 0.1781 0.2349 0.2787 0.3215
1044.82 1073.08 1098.58 1116.15 1131.85
1.106 1.416 1.637 1.744 1.807
(continued on next page)
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S. Solanki et al. / J. Chem. Thermodynamics 56 (2013) 123–135
TABLE 2 (continued) xi
qmix/(kg m3)
VE/(cm3 mol1)
0.3716 1148.63 1.840 0.4229 1164.16 1.826 0.4723 1177.75 1.775 0.5213 1190.17 1.702 0.5731 1202.20 1.597 0.6212 1212.48 1.476 0.6719 1222.55 1.335 0.7224 1231.85 1.177 0.7737 1240.61 1.001 0.8219 1248.26 0.821 0.8764 1256.28 0.598 0.9223 1262.53 0.394 0.9349 1264.16 0.333 (0) (1) (2) E 3 V = 6.947; V = 3.615; V = -0.058; r(V ) = 0.002 cm mol1
u/(m s1)
jS /TPa1
jES /TPa1
1512.2 1523.4 1533.8 1541.1 1549.5 1557.4 1564.3 1571.5 1578.5 1584.8 1590.5 1594.0 1594.8
380.7 370.1 361.3 353.8 346.5 340.0 334.2 328.7 323.5 319.0 314.6 311.7 311.0
76.2 74.7 71.8 67.8 62.9 57.9 51.7 45.4 38.4 31.6 23.0 15.1 12.8
1438.3 1457.5 1478.2 1494.2 1509.3 1527.3 1544.8 1560.0 1572.9 1585.5 1595.6 1603.9 1609.8 1614.6 1618.6 1621.8 1624.6 1625.4
476.7 451.1 427.0 410.0 394.9 378.4 363.5 351.1 340.8 331.1 323.6 317.1 312.0 307.7 304.0 300.7 297.9 297.3
33.0 44.8 55.0 61.2 65.7 69.6 71.8 71.9 70.2 66.9 62.7 56.7 49.3 41.3 32.8 23.2 14.2 12.3
1415.5 1434.8 1454.8 1471.0 1487.7 1506.4 1525.5 1542.7 1557.7 1572.9 1585.0 1596.4 1605.1 1611.1 1615.6 1618.7 1619.8 1619.6
493.7 466.9 442.1 424.3 407.7 390.3 374.1 360.4 348.7 337.5 328.9 320.9 314.6 309.7 305.8 302.5 300.4 300.1
33.1 45.5 55.5 61.9 67.2 71.4 74.2 75.0 74.0 71.4 67.6 62.4 55.6 47.5 38.6 28.3 18.0 15.6
1397.7 1417.2 1438.3 1454.4 1470.8 1490.5 1509.0 1525.2 1540.6 1555.3 1567.5 1577.8 1586.2 1592.1
508.7 480.6 454.1 435.6 418.6 399.9 383.5 369.7 357.5 346.2 337.2 329.4 323.0 318.1
35.2 48.1 59.0 65.5 70.7 75.4 77.8 78.0 76.8 73.7 69.7 63.6 56.1 47.5
ð1Þ ð2Þ 1 E jð0Þ S = 278.6; jS = 158.9; jS = 93.9; r(jS ) = 0.1 TPa
{1-Ethyl-3-methylimidazolium tetrafluoroborate T/K = 293.15 0.1219 1013.90 0.921 0.1776 1043.45 1.377 0.2341 1071.82 1.823 0.2778 1092.45 2.131 0.3209 1111.76 2.405 0.3721 1133.09 2.660 0.4232 1152.77 2.843 0.4727 1170.31 2.948 0.5217 1186.07 2.961 0.5742 1201.42 2.891 0.6217 1214.02 2.756 0.6724 1226.14 2.528 0.7228 1236.96 2.227 0.7725 1246.69 1.878 0.8216 1255.54 1.492 0.8741 1264.27 1.045 0.9218 1271.82 0.634 0.9319 1273.41 0.550 V(0) = 11.863; V(1) = 0.563; V(2) = 4.967; r(VE) = 0.002 cm3 mol1
(i) + a-picoline (j)}
ð1Þ ð2Þ 1 E jð0Þ S = 284.6; jS = 65.0; jS = 46.0; r(jS ) = 0.1 TPa
T/K = 298.15 0.1219 1010.93 1.096 0.1776 1040.53 1.558 0.2341 1068.69 1.983 0.2778 1089.12 2.269 0.3209 1108.07 2.506 0.3721 1129.16 2.735 0.4232 1148.64 2.896 0.4727 1166.05 2.984 0.5217 1181.95 3.008 0.5742 1197.47 2.951 0.6217 1210.21 2.826 0.6724 1222.71 2.635 0.7228 1233.88 2.367 0.7725 1243.95 2.050 0.8216 1252.96 1.679 0.8741 1261.73 1.230 0.9218 1269.01 0.783 0.9319 1270.50 0.686 (0) (1) (2) E 3 V = 12.021; V = 0.591; V = 2.319; r(V ) = 0.002 cm mol1 ð1Þ ð2Þ 1 E jð0Þ S = 298.6; jS = 36.0; jS = 27.2; r(jS ) = 0.1 TPa
T/K = 303.15 0.1219 0.1776 0.2341 0.2778 0.3209 0.3721 0.4232 0.4727 0.5217 0.5742 0.6217 0.6724 0.7228 0.7725
1006.33 1036.16 1064.53 1085.10 1104.33 1125.57 1145.21 1162.72 1178.63 1194.21 1206.93 1219.36 1230.44 1240.41
1.107 1.591 2.036 2.335 2.598 2.838 3.010 3.104 3.123 3.068 2.933 2.727 2.441 2.104
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S. Solanki et al. / J. Chem. Thermodynamics 56 (2013) 123–135 TABLE 2 (continued) xi
qmix/(kg m3)
VE/(cm3 mol1)
0.8216 1249.32 1.713 0.8741 1257.98 1.243 0.9218 1265.26 0.786 0.9319 1266.74 0.686 V(0) = 12.508; V(1) = 0.613; V(2) = 2.963; r(VE) = 0.002 cm3 mol1
u/(m s1)
jS /TPa1
jES /TPa1
1596.9 1600.8 1603.5 1604.0
313.9 310.2 307.4 306.8
38.2 27.5 17.2 15.0
1379.6 1400.0 1422.0 1439.1 1455.6 1475.5 1495.0 1513.6 1530.3 1545.9 1559.0 1571.1 1581.6 1589.0 1593.8 1597.4 1598.2 1598.4
524.2 494.3 466.3 446.6 428.9 409.5 392.1 376.7 363.6 351.6 342.1 333.4 326.0 320.4 316.2 312.6 310.4 310.0
39.1 52.8 64.4 71.5 76.6 81.2 83.8 84.8 83.7 80.4 76.2 70.2 62.9 54.1 44.1 32.5 20.7 18.2
445.6 426.1 402.9 394.0 379.6 366.5 355.8 345.5 336.9 328.5 321.6 315.6 310.4 306.1 302.1 298.8 296.6 295.6
29.2 38.1 47.1 49.9 53.8 56.2 56.8 56.8 55.2 52.9 49.4 44.9 40.1 34.2 27.5 20.7 14.4 11.4
456.6 435.8 412.1 402.7 388.5 375.5 364.8 354.4 345.6 336.8 329.4 322.4 316.3 310.9 306.2 302.5 300.2 299.4
34.6 44.2 52.8 55.6 58.7 60.3 60.3 59.7 57.8 55.3 51.7 47.5 43.0 37.5 30.8 23.7 17.2 13.6
ð1Þ ð2Þ 1 E jð0Þ S = 310.8; jS = 53.3; jS = 37.3; r(jS ) = 0.1 TPa
T/K = 308.15 0.1219 1002.14 1.172 0.1776 1032.07 1.668 0.2341 1060.50 2.121 0.2778 1081.18 2.432 0.3209 1100.37 2.690 0.3721 1121.65 2.933 0.4232 1141.21 3.096 0.4727 1158.68 3.184 0.5217 1174.56 3.196 0.5742 1190.05 3.126 0.6217 1202.85 2.996 0.6724 1215.15 2.771 0.7228 1226.27 2.482 0.7725 1236.19 2.135 0.8216 1245.10 1.737 0.8741 1253.82 1.266 0.9218 1261.08 0.799 0.9319 1262.57 0.699 (0) (1) (2) E 3 V = 12.811; V = 0.331; V = 2.804; r(V ) = 0.003 cm mol1 ð1Þ ð2Þ 1 E jð0Þ S = 336.9; jS = 47.3; jS = 12.4; r(jS ) = 0.1 TPa
{1-Ethyl-3-methylimidazolium tetrafluoroborate (i) + b-picoline (j) T/K = 293.15 0.1217 1024.56 0.915 1479.9 0.1729 1050.57 1.272 1494.7 0.2415 1082.96 1.695 1513.9 0.2711 1096.07 1.854 1521.7 0.3214 1117.16 2.085 1535.6 0.3732 1137.38 2.273 1548.8 0.4219 1154.95 2.389 1560.1 0.4718 1171.59 2.450 1571.8 0.5209 1186.68 2.451 1581.6 0.5723 1201.17 2.389 1591.9 0.6221 1214.02 2.269 1600.3 0.6731 1226.02 2.084 1607.5 0.7212 1236.43 1.866 1614.1 0.7708 1246.34 1.599 1619.1 0.8224 1255.77 1.274 1623.7 0.8713 1264.10 0.940 1627.2 0.9119 1270.62 0.648 1629.0 0.9317 1273.70 0.504 1629.8 V(0) = 9.812; V(1) = 0.152; V(2) = 2.382; r(VE) = 0.002 cm3 mol1 ð1Þ ð2Þ 1 E jð0Þ S = 224.1; jS = 59.4; jS = 7.3; r(jS ) = 0.1 TPa
T/K = 298.15 0.1217 0.1729 0.2415 0.2711 0.3214 0.3732 0.4219 0.4718 0.5209 0.5723 0.6221 0.6731 0.7212 0.7708 0.8224 0.8713 0.9119 0.9317
1020.46 1046.54 1079.02 1092.10 1113.25 1133.44 1151.03 1167.70 1182.83 1197.38 1210.25 1222.36 1232.83 1242.76 1252.24 1260.53 1266.99 1270.00
0.969 1.334 1.766 1.922 2.158 2.341 2.457 2.518 2.520 2.460 2.338 2.161 1.944 1.673 1.348 1.005 0.701 0.546
1465.0 1480.8 1499.7 1507.9 1520.5 1532.8 1543.2 1554.4 1564.0 1574.7 1583.7 1593.0 1601.4 1608.8 1614.9 1619.3 1621.6 1621.8
(continued on next page)
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S. Solanki et al. / J. Chem. Thermodynamics 56 (2013) 123–135
TABLE 2 (continued)
(0)
VE/(cm3 mol1)
qmix/(kg m3)
xi (1)
(2)
E
3
u/(m s1)
jS /TPa1
jES /TPa1
1443.4 1459.7 1481.3 1490.3 1504.5 1519.4 1532.2 1544.1 1556.0 1566.4 1576.1 1585.5 1592.8 1598.7 1604.2 1607.5 1609.0 1609.2
472.1 450.1 423.8 413.7 398.2 383.5 371.3 360.4 350.3 341.4 333.5 326.3 320.5 315.6 311.0 307.7 305.6 304.8
35.0 45.2 55.5 58.8 62.6 65.3 66.1 65.5 64.2 61.1 57.4 52.8 47.4 40.8 33.4 25.4 18.0 14.2
1427.1 1443.9 1465.6 1474.6 1488.8 1503.4 1517.0 1530.0 1541.8 1554.1 1565.4 1576.2 1585.3 1593.7 1599.5 1603.0 1603.9 1603.2
485.4 462.0 434.8 424.3 408.2 393.1 380.0 368.1 357.8 347.8 339.0 331.0 324.4 318.4 313.8 310.4 308.5 308.1
38.5 49.3 59.7 63.0 66.7 69.1 70.3 69.9 68.2 65.6 62.2 57.6 52.4 46.2 38.3 29.7 21.6 17.2
443.6 424.0 407.8 392.2 378.9 366.8 355.7 345.8 337.5 329.4 322.6 316.4 311.0 306.2 302.6 299.0 296.7 295.7
28.9 37.8 44.2 49.1 52.4 54.6 55.4 54.9 53.3 50.8 47.5 43.2 38.6 32.8 26.9 20.0 14.2 11.2
458.4 437.8 420.6 403.7 389.4
29.1 38.4 45.3 50.8 54.6
1
= 10.095; V = 0.097; V = 1.913; r(V ) = 0.002 cm mol ð1Þ ð2Þ 1 E jð0Þ S = 234.9; jS = 74.2; jS = 58.2; r(jS ) = 0.1 TPa V
T/K = 303.15 0.1217 1016.63 1.045 0.1729 1042.83 1.422 0.2415 1075.30 1.850 0.2711 1088.37 2.003 0.3214 1109.49 2.234 0.3732 1129.62 2.406 0.4219 1147.27 2.524 0.4718 1163.94 2.580 0.5209 1179.20 2.591 0.5723 1193.82 2.533 0.6221 1206.88 2.425 0.6731 1219.18 2.263 0.7212 1229.78 2.054 0.7708 1239.81 1.790 0.8224 1249.34 1.464 0.8713 1257.58 1.108 0.9119 1263.93 0.786 0.9317 1266.86 0.617 V(0) = 10.369; V(1) = 0.051; V(2) = 0.944; r(VE) = 0.002 cm3 mol1 ð1Þ ð2Þ 1 E jð0Þ S = 259.3; jS = 67.8; jS = 30.3; r(jS ) = 0.1 TPa
T/K = 308.15 0.1217 1011.73 1.026 0.1729 1038.13 1.425 0.2415 1070.72 1.868 0.2711 1084.01 2.043 0.3214 1105.30 2.291 0.3732 1125.73 2.493 0.4219 1143.60 2.634 0.4718 1160.52 2.714 0.5209 1175.87 2.733 0.5723 1190.64 2.689 0.6221 1203.74 2.583 0.6731 1215.94 2.406 0.7212 1226.48 2.187 0.7708 1236.40 1.907 0.8224 1245.81 1.562 0.8713 1253.89 1.183 0.9119 1260.07 0.836 0.9317 1262.91 0.656 (0) (1) (2) E 3 V = 10.918; V = 0.599; V = 1.498; r(V ) = 0.002 cm mol1 ð1Þ ð2Þ 1 E jð0Þ S = 276.3; jS = 62.1; jS = 63.6; r(jS ) = 0.1 TPa
1-Ethyl-3-methylimidazolium tetrafluoroborate (i) + c-picoline (j) T/K = 293.15 0.1211 1022.19 0.836 1485.0 0.1734 1048.92 1.208 1499.5 0.2215 1072.35 1.550 1512.2 0.2738 1096.49 1.902 1525.0 0.3226 1117.74 2.202 1536.7 0.3709 1137.61 2.472 1548.0 0.4215 1157.13 2.714 1558.7 0.4721 1175.31 2.905 1568.6 0.5207 1191.56 3.039 1576.9 0.5728 1207.52 3.109 1585.7 0.6218 1221.15 3.096 1593.2 0.6731 1234.15 3.013 1600.4 0.7224 1245.20 2.836 1607.0 0.7743 1255.49 2.557 1613.0 0.8203 1263.45 2.224 1617.3 0.8717 1270.96 1.737 1622.3 0.9111 1275.81 1.286 1625.3 0.9312 1278.00 1.031 1626.7 V(0) = 11.955; V(1) = 5.122; V(2) = 0.396; r(VE) = 0.002 cm3 mol1 ð1Þ ð2Þ 1 E jð0Þ S = 216.5; jS = 61.8; jS = 15.0; r(jS ) = 0.1 TPa
T/K = 298.15 0.1211 0.1734 0.2215 0.2738 0.3226
1017.25 1043.93 1067.26 1091.32 1112.60
0.834 1.202 1.532 1.873 2.174
1464.4 1479.3 1492.6 1506.5 1519.3
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S. Solanki et al. / J. Chem. Thermodynamics 56 (2013) 123–135 TABLE 2 (continued) xi
qmix/(kg m3)
VE/(cm3 mol1)
0.3709 1132.52 2.446 0.4215 1152.20 2.700 0.4721 1170.56 2.905 0.5207 1186.91 3.045 0.5728 1203.15 3.138 0.6218 1217.12 3.156 0.6731 1230.36 3.093 0.7224 1241.78 2.949 0.7743 1252.28 2.687 0.8203 1260.27 2.350 0.8717 1267.85 1.863 0.9111 1272.56 1.390 0.9312 1274.64 1.119 V(0) = 11.972; V(1) = 5.869; V(2) = 0.558; r(VE) = 0.003 cm3 mol1
u/(m s1)
jS /TPa1
jES /TPa1
1531.8 1543.8 1554.4 1564.8 1573.8 1582.4 1589.4 1595.7 1601.8 1606.3 1610.6 1613.4 1614.9
376.3 364.2 353.6 344.1 335.6 328.1 321.8 316.3 311.2 307.5 304.1 301.9 300.8
57.3 58.5 58.2 57.2 54.5 51.4 46.7 41.5 35.4 29.2 21.6 15.2 11.9
1448.9 1464.5 1478.1 1492.3 1505.1 1517.3 1529.7 1541.8 1553.0 1564.2 1574.8 1585.1 1594.6 1602.4 1608.5 1612.2 1613.3 1613.3
470.5 448.6 430.7 413.1 398.3 384.9 372.2 360.5 350.3 340.6 332.1 324.2 317.3 311.6 307.3 304.1 302.6 302.1
33.4 43.3 50.3 55.9 59.6 61.9 63.1 63.2 62.3 60.1 57.4 53.6 49.2 43.1 36.9 28.4 20.9 16.8
1428.2 1443.7 1457.6 1472.9 1486.3 1499.9 1514.7 1528.9 1542.6 1557.1 1570.3 1582.6 1593.7 1603.4 1609.8 1612.8 1611.5 1609.7
486.1 463.4 444.4 425.4 409.6 395.0 380.6 367.6 356.1 344.8 335.2 326.4 319.0 312.6 308.1 305.2 304.6 304.7
34.8 44.9 52.3 58.7 62.7 65.6 67.7 68.5 68.2 67.0 64.7 61.1 56.6 50.5 43.8 34.3 25.4 20.4
ð1Þ ð2Þ 1 E jð0Þ S = 231.0; jS = 54.1; jS = 2.9; r(jS ) = 0.1 TPa
T/K = 303.15 0.1211 1012.54 0.838 0.1734 1039.26 1.208 0.2215 1062.71 1.547 0.2738 1086.94 1.903 0.3226 1108.38 2.217 0.3709 1128.45 2.501 0.4215 1148.31 2.769 0.4721 1166.92 2.995 0.5207 1183.59 3.163 0.5728 1200.15 3.285 0.6218 1214.30 3.316 0.6731 1227.81 3.275 0.7224 1239.32 3.136 0.7743 1249.84 2.869 0.8203 1257.85 2.528 0.8717 1265.24 2.013 0.9111 1269.80 1.514 0.9312 1271.69 1.218 V(0) = 12.403; V(1) = 6.763; V(2) = 1.058; r(VE) = 0.003 cm3 mol1 ð1Þ ð2Þ 1 E jð0Þ S = 250.8; jS = 39.1; jS = 59.1; r (jS ) = 0.1 TPa
T/K = 308.15 0.1211 1008.40 0.893 0.1734 1035.43 1.298 0.2215 1059.13 1.664 0.2738 1083.63 2.050 0.3226 1105.18 2.376 0.3709 1125.39 2.675 0.4215 1145.11 2.928 0.4721 1163.65 3.146 0.5207 1180.05 3.285 0.5728 1196.14 3.354 0.6218 1209.95 3.346 0.6731 1222.97 3.249 0.7224 1234.16 3.068 0.7743 1244.37 2.760 0.8203 1252.23 2.394 0.8717 1259.65 1.872 0.9111 1264.37 1.386 0.9312 1266.47 1.108 (0) (1) (2) E 3 V = 12.921; V = 5.556; V = 0.538; r(V ) = 0.003 cm mol1 ð1Þ ð2Þ 1 E jð0Þ S = 273.3; jS = 12.5; jS = 76.1; r (jS ) = 0.1 TPa
The uncertainty in mole fraction value is 1 104. The uncertainty in temperature is 0.01 K. The uncertainty in VE value is 0.1%; atmospheric pressure.
and jES data are negative over entire composition range. While VE values for the present mixtures at equimolar composition vary in order: Py > b-picoline > a-picoline c-picoline; HE values follow the sequence: b-picoline > a-picoline > c-picoline > Py. Further, jES values vary as: a-picoline c-picoline > Py > b-picoline. The HE data of the various (i + j) mixtures can be explained qualitatively, if it is assumed that (i) [emim][BF4] is characterized by strong ionic interactions and Py or a- or b-, or c-picoline are associated entities; (ii) there are ion–dipole interactions between nitrogen and carbon atoms of Py or isomeric picolines with nitrogen and florine atoms of [emim][BF4]; (iii) interactions between i and j weaken self association of Py or isomeric picolines and ionic inter-
action in [emim][BF4] to form (j) monomers; and (iv) monomers of (i) and (j) undergo interactions and may form 1:1 molecular complex. The HE values for {[emim][BF4] (i) + Py (j)} mixture suggest that contribution to HE due to factors (i), (ii), and (iv) far outweigh the contribution due to factor (iii), so that HE values are negative. The introduction of –CH3 group in aromatic ring of pyridine (as in a- or b- or c-picoline) would increase the p-electron density on nitrogen atom of pyridine or isomeric picolines which in turn suggest strong ion–dipole interactions in {[emim][BF4] (i) + isomeric picoline (j)} mixtures as compared to {[emim][BF4] (i) + Py} mixture (j). Consequently, HE values for {[emim][BF4] (i) + a- or b- or c-picoline (j)} mixtures should be less (more negative) than
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TABLE 3 Measured excess molar enthalpies, HE values for the various (i + j) mixtures as a function of mole fraction xi, of component (i) at T/K = 298.15. Also included are the various Hn (n = 0–2) parameters along with standard deviations r (HE). xi
HE/(J mol1)
xi
HE/(J mol1)
{1-Ethyl-3-methylimidazolium tetrafluoroborate (i) + pyridine (j)} 0.1025 147 0.4956 452 0.1335 188 0.5325 453 0.1727 232 0.5890 443 0.2121 280 0.6312 420 0.2654 328 0.6983 381 0.3078 364 0.7567 337 0.3587 405 0.8078 279 0.4112 424 0.8654 212 0.4632 448 0.9123 144 H(0) = 1797; H(1) = 129; H(2) = 171; r(HE) = 3 J mol1 {1-Ethyl-3-methylimidazolium tetrafluoroborate (i) + a-picoline (j)} 0.1132 109 0.5123 408 0.1578 148 0.5734 437 0.2087 194 0.6145 448 0.2467 225 0.6634 453 0.2976 266 0.7145 436 0.3245 286 0.7856 399 0.3789 326 0.8265 360 0.4235 356 0.8723 304 0.4876 395 0.9226 209 H(0) = 1600; H(1) = 1071; H(2) = 550; r(HE) = 3 J mol1 {1-Ethyl-3-methylimidazolium tetrafluoroborate (i) + b-picoline (j)} 0.1256 136 0.5223 369 0.1676 171 0.5990 376 0.2089 205 0.6345 372 0.2578 245 0.6890 360 0.2976 272 0.7356 339 0.3387 294 0.7909 298 0.3898 320 0.8479 244 0.4367 341 0.8890 197 0.4876 362 0.9109 165 H(0) = 1450; H(1) = 483; H(2) = 247; r(HE) = 2 J. mol1
FIGURE 1. Excess molar volumes, VE at 293.15 K: (I) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + pyridine (j)} Expt. ( ), Graph ( ); (II) {1-ethyl-3methylimidazolium tetrafluoroborate (i) + a-picoline (j)} Expt. ( ), Graph ( ); (III) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + b-picoline (j)} Expt. ( ), Graph ( ); (IV) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + cpicoline (j)} Expt. ( ), Graph ( ).
{1-Ethyl-3-methylimidazolium tetrafluoroborate (i) + c-picoline (j)} 0.1110 130 0.5267 436 0.1679 190 0.5908 444 0.2098 234 0.6150 443 0.2387 261 0.6786 423 0.2909 306 0.7234 408 0.3267 330 0.7945 352 0.3790 365 0.8346 303 0.4167 387 0.8890 226 0.4834 417 0.9267 163 H(0) = 1704; H(1) = 629; H(2) = 186; r(HE) = 3 J mol1 The uncertainty in mole fraction value is 1 104; the uncertainty in temperature is 0.01 K; the uncertainty in HE values is 1%; atmospheric pressure.
those of {[emim][BF4] (i) + Py (j)} mixture. This is indeed not true. It may be due to higher molar volumes (at T/K = 298.15) of a(98.96 106 m3 mol1) or b- (97.69 106 m3 mol1) or c(97.88 106 m3 mol1) picolines as compared to Py (80.80 106 m3 mol1) which restrict their approach between the clathrates of [emim][BF4] as compared to Py. Thus contribution to HE values due to factor (iv) will be more in pyridine as compared to picolines. The magnitude and sign of VE and jES data is a cumulative effect of contributions due to (i) breaking of self associated molecules (positive volume); (ii) break down of ionic interactions (positive volume); and (iii) packing effect and ion–dipole interactions between Py or isomeric picoline and [emim][BF4] molecules. The negative values of VE for the investigated mixtures suggest strong ion– dipole interactions (between [emim][BF4] and Py or isomeric picolines) and more closed packing of the constituent of mixtures in mixed state as compared to pure state. Further, temperature coefficient (oVE/oT) and (ojES /oT) is negative. This suggest that there may be a formation of associated species in {[emim][BF4] + Py or isomeric picoline} mixture with increase in temperature which
FIGURE 2. Excess molar volumes, VE at 298.15 K: (I) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + pyridine (j)} Expt. ( ), Graph ( ); (II) {1-ethyl-3methylimidazolium tetrafluoroborate (i) + a-picoline (j)} Expt. ( ), Graph ( ); (III) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + b-picoline (j)} Expt. ( ), Graph ( ); (IV) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + cpicoline (j)} Expt. ( ), Graph ( ).
results in contraction in volume of the mixture and hence negative VE or jES values.
4.1. Graph theory 4.1.1. Excess molar volumes Graph theory deals with the topology of the constituent of the mixtures. The topology of the pure (i)/(j) components changes with the addition of (i) to (j) or vice versa in (i + j) mixtures. Since excess molar volumes, VE reflects change in topology of the constituents of mixtures, it would therefore be worthwhile to analyze the observed VE data of (i + j) mixtures in terms of Graph theory to extract
S. Solanki et al. / J. Chem. Thermodynamics 56 (2013) 123–135
FIGURE 3. Excess molar volumes, VE at 303.15 K: (I) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + pyridine (j)} Expt. ( ), Graph ( ); (II) {1-ethyl-3methylimidazolium tetrafluoroborate (i) + a-picoline (j)} Expt. ( ), Graph ( ); (III) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + b-picoline (j)} Expt. ( ), Graph ( ); (IV) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + cpicoline (j)} Expt. ( ), Graph ( ).
FIGURE 4. Excess molar volumes, VE at 308.15 K: (I) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + pyridine (j)} Expt. ( ), Graph ( ); (II) {1-ethyl-3methylimidazolium tetrafluoroborate (i) + a-picoline (j)} Expt. ( ), Graph ( ); (III) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + b-picoline (j)} Expt. ( ), Graph ( ); (IV) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + cpicoline (j)} Expt. ( ), Graph ( ).
information about the state of components in pure and mixed state along with nature and extent of molecular interaction existing in mixtures. According to this theory [29] VE is given by
V E ¼ aij
hX
xi ð 3 n i Þ m
i1
X
xi ð3 nt Þ1 ;
ð7Þ
where aij is a constant characteristic of (i + j) mixture. The (3ni), (3ni)m (i = i or j) are the connectivity parameters of third degree of the components (i) and (j) in pure and mixed state and are defined [30] by 3
n¼
X m
ðdmm dmn dmo dmp Þ0:5 ;
ð8Þ
131
FIGURE 5. Excess isentropic compressibilities, jES at 293.15 K: (I) {1-ethyl-3methylimidazolium tetrafluoroborate (i) + pyridine (j)} Expt. ( ), Graph ( ); (II) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + a-picoline (j)} Expt. ( ), Graph ( ); (III) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + bpicoline (j)} Expt. ( ), Graph ( ); (IV) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + c-picoline (j)} Expt. ( ), Graph ( ).
FIGURE 6. Excess isentropic compressibilities, jES at 298.15 K: (I) {1-ethyl-3methylimidazolium tetrafluoroborate (i) + pyridine (j)} Expt. ( ), Graph ( ); (II) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + a-picoline (j)} Expt. ( ), Graph ( ); (III) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + bpicoline (j)} Expt. ( ), Graph ( ); (IV) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + c-picoline (j)} Expt. ( ), Graph ( ).
where dmm , etc. have the same significance as described elsewhere [31a,31b]. The (3ni), (3nj)m (i = i or j) parameters have been determined by fitting experimental VE data to equation (7) and only those values that best reproduced the experimental VE data have been retained. Such VE values are plotted in figures 1 to 4 and (3ni), (3nj)m (i = i or j) parameters at various mole fraction of (i), xi are listed in table 4. Examination of data in figures reveals that VE values compare well with their experimental values which in turn suggest that (3ni), (3nj)m (i = i or j) values can be utilized to extract information about the nature of i and j components in pure and mixed state. Various structures were proposed for [emim][BF4], Py or a- or b- or c-picoline and only those structures or combination of structures that yielded 3n/ value (calculated from structural con-
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FIGURE 7. Excess isentropic compressibilities, jES at 303.15 K: (I) {1-ethyl-3methylimidazolium tetrafluoroborate (i) + pyridine (j)} Expt. ( ), Graph ( ); (II) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + a-picoline (j)} Expt. ( ), Graph ( ); (III) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + bpicoline (j)} Expt. ( ), Graph ( ); (IV) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + c-picoline (j)} Expt. ( ), Graph ( ).
FIGURE 8. Excess Isentropic compressibilities, jES at 308.15 K: (I) {1-ethyl-3methylimidazolium tetrafluoroborate (i) + pyridine (j)} Expt. ( ), Graph ( ); (II) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + a-picoline (j)} Expt. ( ), Graph ( ); (III) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + bpicoline (j)} Expt. ( ), Graph ( ); (IV) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + c-picoline (j)} Expt. ( ), Graph ( ).
sideration via equation (8)) comparing well with 3n value (obtained via equation (7)) were taken to be representative structure of that component. For the investigated mixtures, It was assumed that [emim][BF4], Py or a-, b-, or c-picoline exist as molecular entities I, II–IV, V–VIII, IX–XI, and XII–XIII, respectively (scheme 1) and their 3n/ values were determined. The dmm , etc. values for the various vertices are shown in various molecular entities. For [BF4] anion in [emim][BF4], dmm value is taken as 1.5 and for p-electron cloud of aromatic ring of Py or picolines (dm (p) = 1). In evaluating 3n/ values for molecules entity I, it was assumed that [BF4] ion is positioned above the imidazolium ring of [emim][BF4] and [emim][BF4] is characterised by interactions between (i) hydrogen atom attached to C(2) atom of imidazolium ring and two florine atoms of [BF4]; and (ii)
FIGURE 9. Excess molar enthalpies, HE at 298.15 K: (I) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + pyridine (j)} Expt. ( ), Graph ( ); (II) {1-ethyl-3methylimidazolium tetrafluoroborate (i) + a-picoline (j)} Expt. ( ), Graph ( ); (III) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + b-picoline (j)} Expt. ( ), Graph ( ); (IV) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + cpicoline (j)} Expt. ( ), Graph ( ).
hydrogen atom of –CH3 group of imidazolium ring and florine atoms of [BF4]. The 3n/ values for these molecular entities were then calculated to be 1.639, 0.516, 0.706, 1.033, 0.814, 1.050, 1.184, 1.247, 0.788, 1.371, 1.226, 0.847, 0.933 respectively. The 3n values of 1.615 or 1.241, 0.901, 1.182, 1.312 and 1.513 for [emim][BF4], Py, a-, b-, c-picoline (table 4) suggest that [emim][BF4] exist as (molecular entity I; 3n/ = 1.639) monomer; pyridine (mixture of molecular entities III–IV; 3n/ = 0.869); a-picoline (molecular entity VII; 3 / n = 1.184); b-picoline (mixture of molecular entities X–XI; 3 / n = 1.298); c-picoline (molecular entity XII; 3n/ = 0.933) associated molecular entities. Our observations about the state of [emim][BF4] are consistent with earlier observations inferred from IR, Raman spectra and scaled quantum mechanics analysis of [emim][BF4] [32–34] which suggest that (i) [BF4] is positioned over the imidazolium ring and has short contacts not only with H–C(2), but also with a proton of the –CH3 group; and (ii) the ion pair formation strongly influences three antisymmetric B–F stretching vibrations of the anion, and out-of-plane and stretching vibrations of the H–C(2) moiety of the cation. Further, our observations about the state of Py or isomeric picolines are also in agreement with ab initio molecular orbital calculations [35] on the structural, energetic and electronic properties of Py, a-, b-, c-picoline suggesting that p-electron density at C2, C4, and C6 positions in pyridine is less than that in benzene. Thus either one, two or all three electron deficient carbon atoms in Py or isomeric picolines can involve in interaction with p-electron cloud of other molecule to yield associated molecular entity. The (3n/i)m values were then determined to extract information about the state of [emim][BF4] in {[emim][BF4] (i) + Py or a- or bor c-picoline (j)} mixtures. For this purpose it was assumed that studied mixtures may contain molecular entity XIV. In evaluating (3n/i)m value for this molecular entity it was assumed that nitrogen atom and electron deficient carbon atoms of Py or a- or b- or c-picoline are interacting with nitrogen atom (N-3) of imidazolium ring and florine atom of [BF4]. The (3n/i)m value for this molecular entity was then calculated to be 1.729. The (3ni)m values of 1.615 or 1.241 in {[emim][BF4] (i) + Py or a- or b- or c-picoline (j)} mixtures (table 4) suggest that these mixtures are characterized by the presence of molecular entity XIV. The existence of these molecular entities suggest that addition of [emim][BF4] to Py or a- or b- or c-picoline should change H–C(2) vibration of [emim]+ cation, B–F stretching
133
S. Solanki et al. / J. Chem. Thermodynamics 56 (2013) 123–135 TABLE 4 The (3ni) = (3nj)m (i = i or j); aij , v=ij , etc. parameters for the various (i + j) mixtures at T/ K = (293.15, 298.15, 303.15, and 308.15). {1-Ethyl-3-methylimidazolium tetrafluoroborate (i) + pyridine (j)} T/K = 293.15 ( ni) = (3ni)m = 1.615; (3nj) = (3nj)m = 0.901 3 1 aij = 22.779 cm mol 3
v=ij ¼ 17:7 TPa1; v12 = 300.4 TPa1 T/K = 298.15
aij = 23.390 cm3 mol1 v=ij ¼ 15:6 TPa1; v12 = 339.1 TPa1
v=ij = 549 J mol-1; v12 = 1139 J mol1 T/K = 303.15
aij = 24.340 cm3 mol1 v=ij = 16.0 TPa1; v12 = 360.8 TPa1 T/K = 308.15
aij = 24.956 cm3 mol1 v=ij = 17.6 TPa1; v12 = 389.9 TPa1 {1-Ethyl-3-methylimidazolium tetrafluoroborate (i) + a-picoline (j)} T/K = 293.15 ( ni) = (3ni)m = 1.615; (3nj) = (3nj)m = 1.182 3 1 aij = 168.913 cm mol
of [BF4] anion, ring vibrations of Py or isomeric picolines. To substantiate this we analyzed IR spectral data of pure [emim][BF4], Py, b-picoline, and equimolar mixtures of {[emim][BF4] (i) + Py or bpicoline (j)}. It was observed that [emim][BF4], Py, and b-picoline in their pure state showed characteristic vibrations at 3124 cm1 (C–H vibrations), 522 cm1 (B–F stretching) and (1582, 1488, and 1440) cm1 (ring vibrations) [36] respectively. The IR data of {[emim][BF4] (i) + Py or b-picoline (j)} mixtures showed characteristic absorption at 3164 cm1, 3160 cm1 (C–H vibration), 533, 535 cm1 (B–F stretching); (1590, 1496, 1455; 1586, 1493, and 1450) cm1 (ring vibrations) respectively. The Shifting of H– C vibrations towards higher wave number suggest breakdown of interactions between hydrogen atom of imidazolium ring and florine atom of [BF4] anion. Further shifting of ring vibrations towards higher wave number indicates the interaction through nitrogen atom of Py or b-picoline ring [37]. The IR spectral data of investigated mixture suggest that the addition of i to j thus influence H–C vibrations of [emim], B–F stretching of [BF4], and ring vibration of Py or b-picoline. This lends additional support to the existence of molecular entity XIV.
3
v=ij = 75.5 TPa1; v12 = 263.9 TPa1 T/K = 298.15
aij = 171.169 cm3 mol1 v=ij = 93.4 TPa1; v12 = 235.4 TPa1
v=ij = -1055 J mol1; v12 = 365 J mol-1 T/K = 303.15
aij = 178.100 cm3 mol1 v=ij = 90.2 TPa1; v12 = 265.7 TPa1 T/K = 308.15
aij = 182.418 cm3 mol1 v=ij = 102.8 TPa1; v12 = 274.9 TPa1
4.1.2. Excess molar enthalpies and excess isentropic compressibilities Graph theory was next employed to predict HE and jES data of the {[emim][BF4] (i) + Py or a- or b- or c-picoline (j)} mixtures. For this purpose, it was assumed that investigated (i + j) mixtures formation may involve processes; (1) formation of unlike i–jn contacts; (2) unlike contact formation then weakens jn–jn interactions and ionic interactions which leads to the depolymerization of jn to form j monomers; (3) monomers of i and j undergo ion–dipole interactions to form 1:1 molecular complex. If vij ; vjj , and v12 are molar interactions and molar compressibilities interaction parameters for i–j, j–j contacts and specific interactions respectively, then change in thermodynamic properties, DXðX ¼ H or jS ) due to processes (1 to 3) is given [38–40] by
{1-Ethyl-3-methylimidazolium tetrafluoroborate (i) + b-picoline (j)} T/K = 293.15 ( ni) = (3ni)m = 1.615; (3nj) = (3nj)m = 1.312 aij = 331.712 cm3 mol1
xi xj vij v j DX 1 ðX ¼ H or jS Þ ¼ Pj ; i¼i xi v i
ð9Þ
v=ij = 64.3 TPa1; v12 = 214.0 TPa1
x2i xj vjj v j DX 2 ðX ¼ H or jS Þ ¼ P ; j i¼i xi v i
ð10Þ
xi x2j v12 v j DX 3 ðX ¼ H or jS Þ ¼ Pj ; i¼i xi v i
ð11Þ
3
T/K = 298.15
aij = 340.953 cm3 mol1 v=ij = 62.9 TPa1; v12 = 241.8 TPa1
v=ij = 811 J mol1; v12 = 209 J mol1 T/K = 303.15
aij = 350.235 cm3 mol1 v=ij = 75.2 TPa1; v12 = 247.0 TPa1 T/K = 308.15
aij = 368.771 cm3 mol1 v=ij = 85.2 TPa1; v12 = 250.1 TPa1 {1-Ethyl-3-methylimidazolium tetrafluoroborate (i) + c-picoline (j)} T/K = 293.15 (3ni) = (3ni)m = 1.241; (3nj) = (3nj)m = 1.513 aij = 417.782 cm3 mol1 = ij
1
v = 97.9 TPa ; v12 = 187.4 TPa
1
T/K = 298.15 3
1
aij = 418.369 cm mol v=ij = 110.7 TPa1; v12 = 180.2 TPa1
v=ij = 1393 J mol1; v12 = 377 J mol1 T/K = 303.15
aij = 433.438 cm3 mol1 v=ij = 132.5 TPa1; v12 = 163.9 TPa1 T/K = 308.15 aij = 451.568 cm3 mol1 = ij
1
v = 161.5 TPa ; v12 = 128.5 TPa
1
where v i is the molar volume of component (i). The overall change in thermodynamic properties, HE or jES for the investigated (i + j) mixtures due to processes (1 to 3) can, therefore, be expressed by equation (12)
HE or
jES ¼
3 h .X i X DX 1 ¼ x i xj v j xi v i ½vij þ xi vjj þ xj v12 :
ð12Þ
1¼1
Singh et al. [41] have suggested tion (12) reduces to
HE or
jES ¼
v j =v i ¼ 3 ni =3 nj . Consequently equa-
xi xj ð 3 n i = 3 n j Þ ½v þ xi vjj þ xj v12 : xi þ xj ð3 ni =3 nj Þ ij
ð13Þ
For the studied mixtures, it is reasonable to assume that vij ffi vjj ¼ v=ij equation (13) can therefore be expressed by
HE or
jES ¼
xi xj ð 3 n i = 3 n j Þ ½ð1 þ xi Þv=ij þ x=j v12 : xi þ xj ð3 ni =3 nj Þ
ð14Þ
Equation (14) contains two unknown parameters. These parameters were predicted by using HE and jES data at xi = 0.4 and 0.6 and were then utilized to determine HE and jES values of (i + j)
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S. Solanki et al. / J. Chem. Thermodynamics 56 (2013) 123–135
SCHEME 1. Connectivity parameters, 3n/ of the third degree for various molecular entities.
mixtures at other values of xi. Such jES and HE values are plotted in figures 5 to 9 and v=ij and v12 parameters are recorded in table 4. Examination of data in figures reveals that HE and jES values com-
pare well with their experimental values which in turn provide additional support to the various assumptions made in deriving equation (14).
S. Solanki et al. / J. Chem. Thermodynamics 56 (2013) 123–135
5. Conclusion The measured densities and speeds of sound data of the investigated mixtures are employed to predict excess molar volumes, VE and Excess isentropic compressibilities, jES . The topology of the molecules constituting the mixtures have been utilized to extract information about the state of components in pure and mixed state along with molecular entities existing in mixtures. The observed VE, HE, and jES have been analysed in terms of Graph theory. It has been observed that VE, HE, and jES values predicted by Graph theory compare well with experimental values. Even in those cases where the calculated and experimental values are not in agreement, they are of same sign and magnitude. Acknowledgement The Authors are thankful to the Head, Department of Chemistry and authorities of M.D. University, Rohtak, for providing research facilities. References [1] T. Welton, Chem. Rev. 99 (1999) 2071–2084. [2] P. Wasserscheid, T. Welton (Eds.), Ionic Liquid in Synthesis, Wiley-VCH, Weinheim, 2003. [3] C. Reichardt, Org. Process Res. Dev. 11 (2007) 105–113. [4] W. Marczak, S.P. Verevkin, A. Heintz, J. Solution Chem. 32 (2003) 519–526. [5] C.P. Fredlake, J.M. Crosthwaite, D.G. Hert, S.N.V.K. Aki, J.F. Brennecke, J. Chem. Eng. Data 49 (2004) 954–961. [6] M. Abareshi, E.K. Goharshadi, S.M. Zebarjad, J. Mol. Liq. 149 (2009) 66–73. [7] K.A. Kurnia, B. Ariwahjoedi, M.I.A. Mutalib, T. Murugesan, J. Solution Chem. 40 (2011) 470–480. [8] S. Zhang, X. Li, H. Chen, J. Wang, J. Zhang, M. Zhang, J. Chem. Eng. Data 49 (2004) 760–764. [9] M.R. Curras, M.F.C. Gomes, P. Husson, A.A.H. Padua, J. Garcia, J. Chem. Eng. Data 55 (2010) 5504–5512. [10] P. Navia, J. Troncoso, L. Romani, J. Chem. Eng. Data 52 (2007) 1369–1374. [11] A. Stoppa, O. Zech, W. Kunz, R. Buchner, J. Chem. Eng. Data 55 (2010) 1768– 1773. [12] J.S. Yadav, D. Sharma, V.K. Sharma, Thermochim. Acta 489 (2009) 45–52. [13] Neeti, S.K. Jangra, J.S. Yadav, Dimple, V.K. Sharma, J. Mol. Liq. 163 (2011) 36– 45.
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[14] N. Saini, S.K. Jangra, J.S. Yadav, D. Sharma, V.K. Sharma, Thermochim. Acta 518 (2011) 13–26. [15] S.K. Jangra, Neeti, J.S. Yadav, Dimple, V.K. Sharma, Thermochim. Acta 530 (2012) 25–31. [16] E. Scholz, Karl Fischer Titration, Springer-Verlag, Berlin, 1984. [17] J.A. Riddick, W.B. Bunger, T.K. Sakano, Organic Solvents Physical Properties and Methods of Purification, fourth ed., Wiley Interscience, New York, 1986. [18] I. Alonso, I. Mozo, I.G. De la Fuente, J.A. González, J.C. Cobos, J. Mol. Liq. 160 (2011) 180–186. [19] M.S. Bakshi, J. Chem. Soc., Faraday Trans 89 (1993) 2001–2005. [20] W. Marczak, J. Chem. Eng. Data 44 (1999) 621–625. [21] W. Marczak, J. Chem. Eng. Data 41 (1996) 1462–1465. [22] N. Saini, J.S. Yadav, S.K. Jangra, D. Sharma, V.K. Sharma, J. Chem. Thermodyn. 43 (2011) 782–795. [23] G.P. Dubey, M. Sharma, J. Chem. Eng. Data 53 (2008) 1032–1038. [24] Dimple, J.S. Yadav, K.C. Singh, V.K. Sharma, Thermochim. Acta 468 (2008) 108–115. [25] G.C. Benson, O. Kiyohara, J. Chem. Thermodyn. 11 (1979) 1061–1064. [26] Y.A. Sanmamed, P. Navia, D.G. Salgado, J. Troncoso, L. Romaní, J. Chem. Eng. Data 55 (2010) 600–604. [27] J.H. Hildebrand, J.M. Prusnitz, R.L. Scott, Regular and Related Solutions: The Solubility of Gases, Liquids and Solids, Van-Nonstand Reinheld Compound, New York, 1971. [28] O. Redlich, A.T. Kister, Ind. Eng. Chem. 40 (1948) 345–348. [29] P.P. Singh, V.K. Sharma, S.P. Sharma, Thermochim. Acta 106 (1986) 293– 307. [30] P.P. Singh, Thermochim. Acta 66 (1983) 37–73. [31] L.B. Kier, S.H. Yalkowasky, A.A. Sinkula, S.C. Valvani, Physico-chemical Properties of Drugs, Mercel Dekker, New York, 1980 (Chapter 9) (a) p. 282; (b) p. 295. [32] A.K. Sergey, J.D. Paul, E.V. Elena, V.C. Alla, A. Vidis, Helv. Chim. Acta 87 (2004) 2556–2565. [33] Z. Meng, A. Dölle, W.R. Carper, J. Mol. Struct. (THEOCHEM) 585 (2002) 119– 128. [34] T.I. Morrow, E.J. Maginn, J. Phys. Chem. B 106 (2002) 12807–12813. [35] J.E. Del Bene, J. Am. Chem. Soc. 101 (1979) 6184–6189. [36] C.N.R. Rao, Chemical Application of Infrared Spectroscopy, Academic Press, London, 1963. [37] N.N. Greenwoods, K. Wade, J. Chem. Soc. (1960) 1130–1141. [38] M.L. Huggins, J. Phys. Chem. 74 (1970) 371–378. [39] M.L. Huggins, Polymer 12 (1971) 389–399. [40] P.P. Singh, M. Bhatia, J. Chem. Soc. Faraday Trans. 1 85 (1989) 3807–3812. [41] P.P. Singh, R.K. Nigam, K.C. Singh, V.K. Sharma, Thermochim. Acta 46 (1981) 175–191.
JCT 12-105
Contents lists available at SciVerse ScienceDirect
J. Chem. Thermodynamics journal homepage: www.elsevier.com/locate/jct
Topological investigations of binary mixtures containing ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate and pyridine or isomeric picolines Subhash Solanki, Neeti Hooda, V.K. Sharma ⇑ Department of chemistry, M.D. University, Rohtak 124001, India
a r t i c l e
i n f o
Article history: Received 9 March 2012 Received in revised form 29 June 2012 Accepted 2 July 2012 Available online 21 July 2012 Keywords: Excess molar volumes, VE Excess molar enthalpies, HE Excess isentropic compressibilities, jES Connectivity parameter of third degree of a molecule, 3n Interaction parameter, v
a b s t r a c t The densities, q, speeds of sound, u of {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + pyridine or a- or b- or c-picoline (j)} at T/K = (293.15, 298.15, 303.15, and 308.15) and excess molar enthalpies, HE of the same set of mixtures at T/K = (298.15) have been measured over entire mole fraction range using DSA-5000 and 2-drop microcalorimeter. Excess molar volumes, VE and excess isentropic compressibilities, jES values have been predicted by utilizing the measured densities and speeds of sound data. It has been observed that VE, HE, and jES values for the studied mixtures are negative over entire composition. The connectivity parameter of third degree of a molecule, 3n (which in turn depends upon its topology) have been applied to predict (i) state of components of ionic liquid mixtures in their pure and mixed state; (ii) nature and extent of interactions existing in mixtures; and (iii) VE, HE, and jES values. The analysis of VE data in terms of Graph theory (which deals with topology of a molecule) suggest that while 1ethyl-3-methylimidazolium tetrafluoroborate is characterised by electrostatic forces of attraction and exist as monomer; a- or b- or c-picoline exist as associated molecular entities. Further, (i + j) mixtures are characterized by interactions between nitrogen and florine atoms of 1-ethyl-3-methylimidazolium tetrafluoroborate with nitrogen and carbon atoms of pyridine or isomeric picolines to form 1:1 molecular complex. The IR studies also support to this view point. The VE, HE, and jES values predicted by Graph theory compare well with experimental values. Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction Ionic liquids are known to be environmentally benign solvents. These are organic salts composed of cations, anions and are liquids at or near room temperature. In the past decade these liquids have emerged as replacement for traditionally used volatile organic salts as they possess physical and chemical properties like negligible vapour pressure, low melting point, a wide liquid range, high thermal solubility, high electro conductivity, etc. They have also been used as reaction media, separation solvent, novel electrolytes, and catalyst in synthesis [1–3]. The vast majority of work published on physical properties of ionic liquid mixtures relates to the systems based on N-alkylpyridinium and 1-alkyl-3-methylimidazolium cations with chloroaluminate (III) ions. The chloroaluminate ions proved to be unstable in air and the problem was overcome by making use of alternative Cl, Br, BF 4 , PF6 , etc. anions. Despite their importance and interest, thermodynamic data on ionic liquid mixtures reported in literature are limited [4–7] which in turn restrict their applications. 1-Ethyl-3-methylimidazolium tetrafluoroborate is one of the latest investigated ionic liquid and ⇑ Corresponding author. Tel.: +91 9729071881. E-mail addresses: [email protected], [email protected] (V.K. Sharma). 0021-9614/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jct.2012.07.007
thermodynamic data of mixtures relating to this ionic liquid is scarce [8–11]. In recent studies [12–15] Graph theory has been employed successfully to predict excess molar volumes, VE, excess molar enthalpies, HE, excess isentropic compressibilities, jES and excess Gibb’s free energy, GE data of the various binary as well as ternary mixtures comprising of organic solvents. It would be of interest to see how Graph theory describes the VE, HE, and jES values of the investigated binary ionic liquid mixtures. These considerations prompted us to measure densities, speeds of sound and excess molar enthalpies data of {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + pyridine or a- or b- or c-picoline (j)} binary mixtures.
2. Experimental section 1-Ethyl-3-methylimidazolium tetrafluoroborate [emim][BF4] (Fluka, 0.98 GC) was used without further purification. The content of water in ionic liquid was regularly checked using Karl Fischer titration [16] and the content of water was less than 340 ppm. Pyridine (Py) (Fluka, 0.99 GC), a-picoline (Fluka, 0.98 GC), b-picoline (Fluka, 0.99 GC) and c-picoline (Fluka, 0.99 GC) were purified by standard methods [17]. The purities of the purified liquids were checked by measuring their densities and speeds of sound values.
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S. Solanki et al. / J. Chem. Thermodynamics 56 (2013) 123–135
The values for the purified liquids at T/K = (298.15 ± 0.01) are recorded in table 1 and compare well with their literature values [9–11,13,17–21]. Densities, q and speeds of sound, u values of the pure liquids and their binary mixtures were measured using a commercial density and sound analyzer apparatus (Anton Paar DSA 5000) in the manner as described elsewhere [22,23]. The calibration of the apparatus was carried out with double distilled deionised water. The mole fraction of each mixture was obtained with uncertainty of 1 104 from the measured apparent masses of the components. All the measurements were performed on an electric balance. The density and speed of sound can be measured to ±103 kg m3 and 102 m s1 respectively. However, uncertainties in the density and speed of sound measurements are 2 103 kg m3 and 101 m s1 respectively. The uncertainty in VE values predicted from density results is 0.1%. Further, uncertainty in the temperature measurement is ±0.01 K. Excess molar enthalpies, HE for the studied mixtures were measured by a 2-drop calorimeter (model, 4600) supplied by the Calorimeter Sciences Corporation (CSC), USA at T/K = (298.15) in a manner described elsewhere [24]. The uncertainties in the measured HE values are 1%.
jES ¼ jS jidS :
The j values were obtained in the manner suggested by Benson and Kiyohara [25]
id S
j
j j X X T v i a2i T ¼ /i jS;i þ xi v i C p;i i¼i i¼i
i¼i /i
P
ai
2
j i¼i xi C p;i
;
ð4Þ
X E ðX ¼ V or H or ð0Þ
jS Þ
þ X ð1Þ ð2xi 1Þ þ X ð2Þ ð2xj 1Þ2 ;
ð5Þ
ðnÞ
The densities, q, excess molar enthalpies, HE at T/K = (298.15) and speeds of sound, u, data of {[emim][BF4] (i) + Py or a-, b-, or c-picoline (j)} mixtures measured as a function of composition at T/K = (293.15, 298.15, 303.15, and 308.15) are recorded in tables 2 and 3. Excess molar volumes, VE and excess isentropic compressibilities, jES for the various (i + j) mixtures were determined from their measured densities and speeds of sound data using j j X X VE ¼ xi Mi ðqÞ1 xi M i ðqi Þ1 ; i¼i
! Pj
where /i is the volume fraction of component (i) in the mixed state jS;i , v i , ai , and C p;i are isentropic compressibility, molar volume, thermal expansion coefficient, and molar heat capacity respectively of the pure component (i). The C p for liquids were taken from literature [14,26] and a values for [emim][BF4] as well as liquids were predicted by employing presented experimental data [27]. Such jES values for the investigated mixtures are recorded in table 2. The VE, HE, and jES values for the studied (i + j) mixtures are plotted in figures 1 to 9. The VE, HE, and jES data of the investigated mixtures were fitted to Redlich–Kister equation [28]:
¼ xi xj ½X 3. Results
ð3Þ
id S
ð1Þ
i¼i
jS ¼ ðqu2 Þ1 ;
ð2Þ
where xi , Mi, and qi are the mole fraction, molar mass and density of component (i). Excess isentropic compressibilities, jES for the various (i + j) mixtures were determined using
where X ðn ¼ 0—2Þ, etc. are the parameters characteristic of (i + j) mixtures. These parameters were determined by fitting XE (X = V or H or jS ) data to equation (5) using least-squares optimization. Such parameters along with standard deviations, r (XE) (X = V or H or jS ) defined by
rðX E ÞðX ¼ V or H or jS Þ ¼
X 0:5 2 ðm nÞ ; X Eexptl X Ecalc:equationð4Þ
ð6Þ
where m is the number of data points, n is the number of adjustable parameters in equation (6) are listed in tables 2 and 3. 4. Discussion We are unaware of any VE, HE, and jES data for the investigated mixtures with which to compare our results. The measured VE, HE,
TABLE 1 Comparison of densities, q and speeds of sound, u data of pure liquids with their literature values at T/K = (293.15, 298.15, 303.15, 308.15). Liquids
1-Ethyl-3-methylimidazolium tetrafluoroborate
Pyridine
a-picoline
b-picoline
c-picoline
Temperature/K
q/(kg m3)
u/(m s1)
(Expt.)
(Lit.)
(Expt.)
293.15 298.15
1283.89 1279.91
1631.1 1619.4
303.15
1276.26
308.15
1272.07
1284.3 [9] 1279.6 [10] 1280.07 [11] 1276.5 [9] 1275.7 [10] 1271.9 [10] 1272.48 [11]
293.15 298.15 303.15 308.15 293.15 298.15 303.15 308.15 293.15 298.15 303.15 308.15 293.15 298.15 303.15 308.15
983.191 978.249 973.224 968.166 944.401 939.802 935.117 930.414 956.581 952.002 947.449 942.831 955.099 950.179 945.413 940.821
978.24 [17]
939.81 [17]
951.97 [17]
950.20 [13]
(Lit.)
1607.6 1596.3 1442.0 1417.8 1398.0 1377.1 1400.5 1380.1 1361.0 1339.9 1445.9 1424.0 1404.1 1384.0 1451.1 1431.5 1410.7 1389.9
1436.77 [18] 1418.0 [19] 1397.02 [18]
1379.18 [20]
1423.08 [21]
1431.89 [19]
The uncertainty in temperature is 0.01 K; The uncertainty in density value ±103 kg m3; The uncertainty in speed of sound value is 101 m s1; atmospheric pressure.
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TABLE 2 Measured densities, q; excess molar volumes, VE; speeds of sound, u; isentropic compressibilities, jS ; and excess isentropic compressibilities, jES data for the various (i + j) mixtures as a function of mole fraction, xi, of component (i) at T/K = (293.15, 298.15, 303.15, and 308.15). Also included are the various X(n) (n = 0–2) parameters along with standard deviations r(XE) (X = V or jS ).
qmix/(kg m3)
xi
VE/(cm3 mol1)
u/(m s1)
jS /TPa1
jES /TPa1
427.9 406.7 388.8 376.9 366.6 356.0 346.7 339.2 332.2 326.0 320.6 315.3 310.6 306.2 302.6 298.8 296.2 295.5
37.2 47.4 54.2 57.5 59.4 60.2 59.4 57.2 54.6 50.6 46.6 41.9 36.7 31.0 25.1 18.3 11.9 10.1
1466.6 1486.7 1505.5 1517.7 1528.8 1541.1 1550.9 1560.4 1568.3 1575.5 1582.6 1589.2 1595.2 1601.3 1607.0 1612.2 1616.0 1616.8
441.1 418.2 398.5 386.0 375.2 364.0 354.6 346.3 339.3 333.0 327.2 321.9 317.1 312.5 308.5 304.5 301.5 300.9
41.6 52.8 60.6 63.9 65.6 66.3 64.9 62.7 59.4 54.9 50.5 45.1 39.2 33.1 27.0 19.4 12.8 10.8
1450.1 1470.9 1489.4 1502.2 1513.9 1525.0 1536.1 1544.6 1552.8 1561.4 1568.1 1575.5 1583.1 1589.7 1595.8 1602.0 1605.5 1606.2
453.2 429.0 408.8 395.5 384.0 372.9 362.7 354.6 347.2 340.0 334.2 328.4 322.9 317.9 313.6 309.2 306.3 305.6
45.3 57.2 64.7 68.2 70.2 70.1 68.9 66.0 62.5 58.2 53.2 47.8 42.1 35.6 29.2 21.5 14.1 12.0
1431.6 1453.6 1473.3 1487.6 1499.2
467.0 441.0 419.3 404.8 393.1
48.7 61.6 69.8 74.0 75.6
1-Ethyl-3-methylimidazolium tetrafluoroborate (i) + pyridine (j) T/K = 293.15 0.1225 1057.86 0.940 1486.4 0.1781 1085.74 1.225 1504.8 0.2349 1111.05 1.440 1521.5 0.2787 1128.56 1.550 1533.4 0.3215 1144.24 1.622 1543.9 0.3716 1160.99 1.666 1555.6 0.4229 1176.47 1.663 1565.7 0.4723 1189.98 1.620 1574.0 0.5213 1202.28 1.552 1582.4 0.5731 1214.14 1.447 1589.6 0.6212 1224.23 1.324 1596.3 0.6719 1234.08 1.178 1603.2 0.7224 1243.17 1.015 1609.3 0.7737 1251.76 0.839 1615.2 0.8219 1259.31 0.664 1619.9 0.8764 1267.33 0.461 1625.1 0.9223 1273.71 0.287 1628.2 0.9349 1275.41 0.240 1628.9 V(0) = 6.341; V(1) = 2.988; V(2) = 0.274; r(VE) = 0.001 cm3 mol1 ð1Þ ð2Þ 1 E jð0Þ S = 223.3; jS = 117.4; jS = 58.8; r(jS ) = 0.1 TPa
T/K = 298.15 0.1225 0.1781 0.2349 0.2787 0.3215 0.3716 0.4229 0.4723 0.5213 0.5731 0.6212 0.6719 0.7224 0.7737 0.8219 0.8764 0.9223 0.9349 V(0) = -6.511; V(1) = 3.305;
1053.89 1.022 1081.91 1.317 1107.24 1.532 1124.75 1.640 1140.37 1.704 1156.91 1.725 1172.38 1.717 1185.87 1.667 1198.15 1.592 1209.97 1.478 1220.11 1.354 1230.00 1.206 1239.16 1.045 1247.81 0.869 1255.42 0.695 1263.49 0.491 1269.86 0.312 1271.55 0.262 V(2) = -0.889; r(VE) = 0.002 cm3 mol1
ð1Þ ð2Þ 1 E jð0Þ S = 243.3; jS = 137.8; jS = 71.0; r(jS ) = 0.1 TPa
T/K = 303.15 0.1225 1049.31 1.055 0.1781 1077.49 1.359 0.2349 1102.93 1.576 0.2787 1120.49 1.685 0.3215 1136.25 1.756 0.3716 1152.96 1.786 0.4229 1168.48 1.777 0.4723 1182.12 1.735 0.5213 1194.47 1.660 0.5731 1206.44 1.553 0.6212 1216.67 1.433 0.6719 1226.63 1.285 0.7224 1235.85 1.124 0.7737 1244.54 0.945 0.8219 1252.16 0.767 0.8764 1260.17 0.548 0.9223 1266.47 0.355 0.9349 1268.13 0.299 V(0) = 6.776; V(1) = 3.138; V(2) = 1.153; r(VE) = 0.002 cm3 mol1 ð1Þ ð2Þ 1 E jð0Þ S = 257.0; jS = 147.4; jS = 91.2; r(jS ) = 0.1 TPa
T/K = 308.15 0.1225 0.1781 0.2349 0.2787 0.3215
1044.82 1073.08 1098.58 1116.15 1131.85
1.106 1.416 1.637 1.744 1.807
(continued on next page)
126
S. Solanki et al. / J. Chem. Thermodynamics 56 (2013) 123–135
TABLE 2 (continued) xi
qmix/(kg m3)
VE/(cm3 mol1)
0.3716 1148.63 1.840 0.4229 1164.16 1.826 0.4723 1177.75 1.775 0.5213 1190.17 1.702 0.5731 1202.20 1.597 0.6212 1212.48 1.476 0.6719 1222.55 1.335 0.7224 1231.85 1.177 0.7737 1240.61 1.001 0.8219 1248.26 0.821 0.8764 1256.28 0.598 0.9223 1262.53 0.394 0.9349 1264.16 0.333 (0) (1) (2) E 3 V = 6.947; V = 3.615; V = -0.058; r(V ) = 0.002 cm mol1
u/(m s1)
jS /TPa1
jES /TPa1
1512.2 1523.4 1533.8 1541.1 1549.5 1557.4 1564.3 1571.5 1578.5 1584.8 1590.5 1594.0 1594.8
380.7 370.1 361.3 353.8 346.5 340.0 334.2 328.7 323.5 319.0 314.6 311.7 311.0
76.2 74.7 71.8 67.8 62.9 57.9 51.7 45.4 38.4 31.6 23.0 15.1 12.8
1438.3 1457.5 1478.2 1494.2 1509.3 1527.3 1544.8 1560.0 1572.9 1585.5 1595.6 1603.9 1609.8 1614.6 1618.6 1621.8 1624.6 1625.4
476.7 451.1 427.0 410.0 394.9 378.4 363.5 351.1 340.8 331.1 323.6 317.1 312.0 307.7 304.0 300.7 297.9 297.3
33.0 44.8 55.0 61.2 65.7 69.6 71.8 71.9 70.2 66.9 62.7 56.7 49.3 41.3 32.8 23.2 14.2 12.3
1415.5 1434.8 1454.8 1471.0 1487.7 1506.4 1525.5 1542.7 1557.7 1572.9 1585.0 1596.4 1605.1 1611.1 1615.6 1618.7 1619.8 1619.6
493.7 466.9 442.1 424.3 407.7 390.3 374.1 360.4 348.7 337.5 328.9 320.9 314.6 309.7 305.8 302.5 300.4 300.1
33.1 45.5 55.5 61.9 67.2 71.4 74.2 75.0 74.0 71.4 67.6 62.4 55.6 47.5 38.6 28.3 18.0 15.6
1397.7 1417.2 1438.3 1454.4 1470.8 1490.5 1509.0 1525.2 1540.6 1555.3 1567.5 1577.8 1586.2 1592.1
508.7 480.6 454.1 435.6 418.6 399.9 383.5 369.7 357.5 346.2 337.2 329.4 323.0 318.1
35.2 48.1 59.0 65.5 70.7 75.4 77.8 78.0 76.8 73.7 69.7 63.6 56.1 47.5
ð1Þ ð2Þ 1 E jð0Þ S = 278.6; jS = 158.9; jS = 93.9; r(jS ) = 0.1 TPa
{1-Ethyl-3-methylimidazolium tetrafluoroborate T/K = 293.15 0.1219 1013.90 0.921 0.1776 1043.45 1.377 0.2341 1071.82 1.823 0.2778 1092.45 2.131 0.3209 1111.76 2.405 0.3721 1133.09 2.660 0.4232 1152.77 2.843 0.4727 1170.31 2.948 0.5217 1186.07 2.961 0.5742 1201.42 2.891 0.6217 1214.02 2.756 0.6724 1226.14 2.528 0.7228 1236.96 2.227 0.7725 1246.69 1.878 0.8216 1255.54 1.492 0.8741 1264.27 1.045 0.9218 1271.82 0.634 0.9319 1273.41 0.550 V(0) = 11.863; V(1) = 0.563; V(2) = 4.967; r(VE) = 0.002 cm3 mol1
(i) + a-picoline (j)}
ð1Þ ð2Þ 1 E jð0Þ S = 284.6; jS = 65.0; jS = 46.0; r(jS ) = 0.1 TPa
T/K = 298.15 0.1219 1010.93 1.096 0.1776 1040.53 1.558 0.2341 1068.69 1.983 0.2778 1089.12 2.269 0.3209 1108.07 2.506 0.3721 1129.16 2.735 0.4232 1148.64 2.896 0.4727 1166.05 2.984 0.5217 1181.95 3.008 0.5742 1197.47 2.951 0.6217 1210.21 2.826 0.6724 1222.71 2.635 0.7228 1233.88 2.367 0.7725 1243.95 2.050 0.8216 1252.96 1.679 0.8741 1261.73 1.230 0.9218 1269.01 0.783 0.9319 1270.50 0.686 (0) (1) (2) E 3 V = 12.021; V = 0.591; V = 2.319; r(V ) = 0.002 cm mol1 ð1Þ ð2Þ 1 E jð0Þ S = 298.6; jS = 36.0; jS = 27.2; r(jS ) = 0.1 TPa
T/K = 303.15 0.1219 0.1776 0.2341 0.2778 0.3209 0.3721 0.4232 0.4727 0.5217 0.5742 0.6217 0.6724 0.7228 0.7725
1006.33 1036.16 1064.53 1085.10 1104.33 1125.57 1145.21 1162.72 1178.63 1194.21 1206.93 1219.36 1230.44 1240.41
1.107 1.591 2.036 2.335 2.598 2.838 3.010 3.104 3.123 3.068 2.933 2.727 2.441 2.104
127
S. Solanki et al. / J. Chem. Thermodynamics 56 (2013) 123–135 TABLE 2 (continued) xi
qmix/(kg m3)
VE/(cm3 mol1)
0.8216 1249.32 1.713 0.8741 1257.98 1.243 0.9218 1265.26 0.786 0.9319 1266.74 0.686 V(0) = 12.508; V(1) = 0.613; V(2) = 2.963; r(VE) = 0.002 cm3 mol1
u/(m s1)
jS /TPa1
jES /TPa1
1596.9 1600.8 1603.5 1604.0
313.9 310.2 307.4 306.8
38.2 27.5 17.2 15.0
1379.6 1400.0 1422.0 1439.1 1455.6 1475.5 1495.0 1513.6 1530.3 1545.9 1559.0 1571.1 1581.6 1589.0 1593.8 1597.4 1598.2 1598.4
524.2 494.3 466.3 446.6 428.9 409.5 392.1 376.7 363.6 351.6 342.1 333.4 326.0 320.4 316.2 312.6 310.4 310.0
39.1 52.8 64.4 71.5 76.6 81.2 83.8 84.8 83.7 80.4 76.2 70.2 62.9 54.1 44.1 32.5 20.7 18.2
445.6 426.1 402.9 394.0 379.6 366.5 355.8 345.5 336.9 328.5 321.6 315.6 310.4 306.1 302.1 298.8 296.6 295.6
29.2 38.1 47.1 49.9 53.8 56.2 56.8 56.8 55.2 52.9 49.4 44.9 40.1 34.2 27.5 20.7 14.4 11.4
456.6 435.8 412.1 402.7 388.5 375.5 364.8 354.4 345.6 336.8 329.4 322.4 316.3 310.9 306.2 302.5 300.2 299.4
34.6 44.2 52.8 55.6 58.7 60.3 60.3 59.7 57.8 55.3 51.7 47.5 43.0 37.5 30.8 23.7 17.2 13.6
ð1Þ ð2Þ 1 E jð0Þ S = 310.8; jS = 53.3; jS = 37.3; r(jS ) = 0.1 TPa
T/K = 308.15 0.1219 1002.14 1.172 0.1776 1032.07 1.668 0.2341 1060.50 2.121 0.2778 1081.18 2.432 0.3209 1100.37 2.690 0.3721 1121.65 2.933 0.4232 1141.21 3.096 0.4727 1158.68 3.184 0.5217 1174.56 3.196 0.5742 1190.05 3.126 0.6217 1202.85 2.996 0.6724 1215.15 2.771 0.7228 1226.27 2.482 0.7725 1236.19 2.135 0.8216 1245.10 1.737 0.8741 1253.82 1.266 0.9218 1261.08 0.799 0.9319 1262.57 0.699 (0) (1) (2) E 3 V = 12.811; V = 0.331; V = 2.804; r(V ) = 0.003 cm mol1 ð1Þ ð2Þ 1 E jð0Þ S = 336.9; jS = 47.3; jS = 12.4; r(jS ) = 0.1 TPa
{1-Ethyl-3-methylimidazolium tetrafluoroborate (i) + b-picoline (j) T/K = 293.15 0.1217 1024.56 0.915 1479.9 0.1729 1050.57 1.272 1494.7 0.2415 1082.96 1.695 1513.9 0.2711 1096.07 1.854 1521.7 0.3214 1117.16 2.085 1535.6 0.3732 1137.38 2.273 1548.8 0.4219 1154.95 2.389 1560.1 0.4718 1171.59 2.450 1571.8 0.5209 1186.68 2.451 1581.6 0.5723 1201.17 2.389 1591.9 0.6221 1214.02 2.269 1600.3 0.6731 1226.02 2.084 1607.5 0.7212 1236.43 1.866 1614.1 0.7708 1246.34 1.599 1619.1 0.8224 1255.77 1.274 1623.7 0.8713 1264.10 0.940 1627.2 0.9119 1270.62 0.648 1629.0 0.9317 1273.70 0.504 1629.8 V(0) = 9.812; V(1) = 0.152; V(2) = 2.382; r(VE) = 0.002 cm3 mol1 ð1Þ ð2Þ 1 E jð0Þ S = 224.1; jS = 59.4; jS = 7.3; r(jS ) = 0.1 TPa
T/K = 298.15 0.1217 0.1729 0.2415 0.2711 0.3214 0.3732 0.4219 0.4718 0.5209 0.5723 0.6221 0.6731 0.7212 0.7708 0.8224 0.8713 0.9119 0.9317
1020.46 1046.54 1079.02 1092.10 1113.25 1133.44 1151.03 1167.70 1182.83 1197.38 1210.25 1222.36 1232.83 1242.76 1252.24 1260.53 1266.99 1270.00
0.969 1.334 1.766 1.922 2.158 2.341 2.457 2.518 2.520 2.460 2.338 2.161 1.944 1.673 1.348 1.005 0.701 0.546
1465.0 1480.8 1499.7 1507.9 1520.5 1532.8 1543.2 1554.4 1564.0 1574.7 1583.7 1593.0 1601.4 1608.8 1614.9 1619.3 1621.6 1621.8
(continued on next page)
128
S. Solanki et al. / J. Chem. Thermodynamics 56 (2013) 123–135
TABLE 2 (continued)
(0)
VE/(cm3 mol1)
qmix/(kg m3)
xi (1)
(2)
E
3
u/(m s1)
jS /TPa1
jES /TPa1
1443.4 1459.7 1481.3 1490.3 1504.5 1519.4 1532.2 1544.1 1556.0 1566.4 1576.1 1585.5 1592.8 1598.7 1604.2 1607.5 1609.0 1609.2
472.1 450.1 423.8 413.7 398.2 383.5 371.3 360.4 350.3 341.4 333.5 326.3 320.5 315.6 311.0 307.7 305.6 304.8
35.0 45.2 55.5 58.8 62.6 65.3 66.1 65.5 64.2 61.1 57.4 52.8 47.4 40.8 33.4 25.4 18.0 14.2
1427.1 1443.9 1465.6 1474.6 1488.8 1503.4 1517.0 1530.0 1541.8 1554.1 1565.4 1576.2 1585.3 1593.7 1599.5 1603.0 1603.9 1603.2
485.4 462.0 434.8 424.3 408.2 393.1 380.0 368.1 357.8 347.8 339.0 331.0 324.4 318.4 313.8 310.4 308.5 308.1
38.5 49.3 59.7 63.0 66.7 69.1 70.3 69.9 68.2 65.6 62.2 57.6 52.4 46.2 38.3 29.7 21.6 17.2
443.6 424.0 407.8 392.2 378.9 366.8 355.7 345.8 337.5 329.4 322.6 316.4 311.0 306.2 302.6 299.0 296.7 295.7
28.9 37.8 44.2 49.1 52.4 54.6 55.4 54.9 53.3 50.8 47.5 43.2 38.6 32.8 26.9 20.0 14.2 11.2
458.4 437.8 420.6 403.7 389.4
29.1 38.4 45.3 50.8 54.6
1
= 10.095; V = 0.097; V = 1.913; r(V ) = 0.002 cm mol ð1Þ ð2Þ 1 E jð0Þ S = 234.9; jS = 74.2; jS = 58.2; r(jS ) = 0.1 TPa V
T/K = 303.15 0.1217 1016.63 1.045 0.1729 1042.83 1.422 0.2415 1075.30 1.850 0.2711 1088.37 2.003 0.3214 1109.49 2.234 0.3732 1129.62 2.406 0.4219 1147.27 2.524 0.4718 1163.94 2.580 0.5209 1179.20 2.591 0.5723 1193.82 2.533 0.6221 1206.88 2.425 0.6731 1219.18 2.263 0.7212 1229.78 2.054 0.7708 1239.81 1.790 0.8224 1249.34 1.464 0.8713 1257.58 1.108 0.9119 1263.93 0.786 0.9317 1266.86 0.617 V(0) = 10.369; V(1) = 0.051; V(2) = 0.944; r(VE) = 0.002 cm3 mol1 ð1Þ ð2Þ 1 E jð0Þ S = 259.3; jS = 67.8; jS = 30.3; r(jS ) = 0.1 TPa
T/K = 308.15 0.1217 1011.73 1.026 0.1729 1038.13 1.425 0.2415 1070.72 1.868 0.2711 1084.01 2.043 0.3214 1105.30 2.291 0.3732 1125.73 2.493 0.4219 1143.60 2.634 0.4718 1160.52 2.714 0.5209 1175.87 2.733 0.5723 1190.64 2.689 0.6221 1203.74 2.583 0.6731 1215.94 2.406 0.7212 1226.48 2.187 0.7708 1236.40 1.907 0.8224 1245.81 1.562 0.8713 1253.89 1.183 0.9119 1260.07 0.836 0.9317 1262.91 0.656 (0) (1) (2) E 3 V = 10.918; V = 0.599; V = 1.498; r(V ) = 0.002 cm mol1 ð1Þ ð2Þ 1 E jð0Þ S = 276.3; jS = 62.1; jS = 63.6; r(jS ) = 0.1 TPa
1-Ethyl-3-methylimidazolium tetrafluoroborate (i) + c-picoline (j) T/K = 293.15 0.1211 1022.19 0.836 1485.0 0.1734 1048.92 1.208 1499.5 0.2215 1072.35 1.550 1512.2 0.2738 1096.49 1.902 1525.0 0.3226 1117.74 2.202 1536.7 0.3709 1137.61 2.472 1548.0 0.4215 1157.13 2.714 1558.7 0.4721 1175.31 2.905 1568.6 0.5207 1191.56 3.039 1576.9 0.5728 1207.52 3.109 1585.7 0.6218 1221.15 3.096 1593.2 0.6731 1234.15 3.013 1600.4 0.7224 1245.20 2.836 1607.0 0.7743 1255.49 2.557 1613.0 0.8203 1263.45 2.224 1617.3 0.8717 1270.96 1.737 1622.3 0.9111 1275.81 1.286 1625.3 0.9312 1278.00 1.031 1626.7 V(0) = 11.955; V(1) = 5.122; V(2) = 0.396; r(VE) = 0.002 cm3 mol1 ð1Þ ð2Þ 1 E jð0Þ S = 216.5; jS = 61.8; jS = 15.0; r(jS ) = 0.1 TPa
T/K = 298.15 0.1211 0.1734 0.2215 0.2738 0.3226
1017.25 1043.93 1067.26 1091.32 1112.60
0.834 1.202 1.532 1.873 2.174
1464.4 1479.3 1492.6 1506.5 1519.3
129
S. Solanki et al. / J. Chem. Thermodynamics 56 (2013) 123–135 TABLE 2 (continued) xi
qmix/(kg m3)
VE/(cm3 mol1)
0.3709 1132.52 2.446 0.4215 1152.20 2.700 0.4721 1170.56 2.905 0.5207 1186.91 3.045 0.5728 1203.15 3.138 0.6218 1217.12 3.156 0.6731 1230.36 3.093 0.7224 1241.78 2.949 0.7743 1252.28 2.687 0.8203 1260.27 2.350 0.8717 1267.85 1.863 0.9111 1272.56 1.390 0.9312 1274.64 1.119 V(0) = 11.972; V(1) = 5.869; V(2) = 0.558; r(VE) = 0.003 cm3 mol1
u/(m s1)
jS /TPa1
jES /TPa1
1531.8 1543.8 1554.4 1564.8 1573.8 1582.4 1589.4 1595.7 1601.8 1606.3 1610.6 1613.4 1614.9
376.3 364.2 353.6 344.1 335.6 328.1 321.8 316.3 311.2 307.5 304.1 301.9 300.8
57.3 58.5 58.2 57.2 54.5 51.4 46.7 41.5 35.4 29.2 21.6 15.2 11.9
1448.9 1464.5 1478.1 1492.3 1505.1 1517.3 1529.7 1541.8 1553.0 1564.2 1574.8 1585.1 1594.6 1602.4 1608.5 1612.2 1613.3 1613.3
470.5 448.6 430.7 413.1 398.3 384.9 372.2 360.5 350.3 340.6 332.1 324.2 317.3 311.6 307.3 304.1 302.6 302.1
33.4 43.3 50.3 55.9 59.6 61.9 63.1 63.2 62.3 60.1 57.4 53.6 49.2 43.1 36.9 28.4 20.9 16.8
1428.2 1443.7 1457.6 1472.9 1486.3 1499.9 1514.7 1528.9 1542.6 1557.1 1570.3 1582.6 1593.7 1603.4 1609.8 1612.8 1611.5 1609.7
486.1 463.4 444.4 425.4 409.6 395.0 380.6 367.6 356.1 344.8 335.2 326.4 319.0 312.6 308.1 305.2 304.6 304.7
34.8 44.9 52.3 58.7 62.7 65.6 67.7 68.5 68.2 67.0 64.7 61.1 56.6 50.5 43.8 34.3 25.4 20.4
ð1Þ ð2Þ 1 E jð0Þ S = 231.0; jS = 54.1; jS = 2.9; r(jS ) = 0.1 TPa
T/K = 303.15 0.1211 1012.54 0.838 0.1734 1039.26 1.208 0.2215 1062.71 1.547 0.2738 1086.94 1.903 0.3226 1108.38 2.217 0.3709 1128.45 2.501 0.4215 1148.31 2.769 0.4721 1166.92 2.995 0.5207 1183.59 3.163 0.5728 1200.15 3.285 0.6218 1214.30 3.316 0.6731 1227.81 3.275 0.7224 1239.32 3.136 0.7743 1249.84 2.869 0.8203 1257.85 2.528 0.8717 1265.24 2.013 0.9111 1269.80 1.514 0.9312 1271.69 1.218 V(0) = 12.403; V(1) = 6.763; V(2) = 1.058; r(VE) = 0.003 cm3 mol1 ð1Þ ð2Þ 1 E jð0Þ S = 250.8; jS = 39.1; jS = 59.1; r (jS ) = 0.1 TPa
T/K = 308.15 0.1211 1008.40 0.893 0.1734 1035.43 1.298 0.2215 1059.13 1.664 0.2738 1083.63 2.050 0.3226 1105.18 2.376 0.3709 1125.39 2.675 0.4215 1145.11 2.928 0.4721 1163.65 3.146 0.5207 1180.05 3.285 0.5728 1196.14 3.354 0.6218 1209.95 3.346 0.6731 1222.97 3.249 0.7224 1234.16 3.068 0.7743 1244.37 2.760 0.8203 1252.23 2.394 0.8717 1259.65 1.872 0.9111 1264.37 1.386 0.9312 1266.47 1.108 (0) (1) (2) E 3 V = 12.921; V = 5.556; V = 0.538; r(V ) = 0.003 cm mol1 ð1Þ ð2Þ 1 E jð0Þ S = 273.3; jS = 12.5; jS = 76.1; r (jS ) = 0.1 TPa
The uncertainty in mole fraction value is 1 104. The uncertainty in temperature is 0.01 K. The uncertainty in VE value is 0.1%; atmospheric pressure.
and jES data are negative over entire composition range. While VE values for the present mixtures at equimolar composition vary in order: Py > b-picoline > a-picoline c-picoline; HE values follow the sequence: b-picoline > a-picoline > c-picoline > Py. Further, jES values vary as: a-picoline c-picoline > Py > b-picoline. The HE data of the various (i + j) mixtures can be explained qualitatively, if it is assumed that (i) [emim][BF4] is characterized by strong ionic interactions and Py or a- or b-, or c-picoline are associated entities; (ii) there are ion–dipole interactions between nitrogen and carbon atoms of Py or isomeric picolines with nitrogen and florine atoms of [emim][BF4]; (iii) interactions between i and j weaken self association of Py or isomeric picolines and ionic inter-
action in [emim][BF4] to form (j) monomers; and (iv) monomers of (i) and (j) undergo interactions and may form 1:1 molecular complex. The HE values for {[emim][BF4] (i) + Py (j)} mixture suggest that contribution to HE due to factors (i), (ii), and (iv) far outweigh the contribution due to factor (iii), so that HE values are negative. The introduction of –CH3 group in aromatic ring of pyridine (as in a- or b- or c-picoline) would increase the p-electron density on nitrogen atom of pyridine or isomeric picolines which in turn suggest strong ion–dipole interactions in {[emim][BF4] (i) + isomeric picoline (j)} mixtures as compared to {[emim][BF4] (i) + Py} mixture (j). Consequently, HE values for {[emim][BF4] (i) + a- or b- or c-picoline (j)} mixtures should be less (more negative) than
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TABLE 3 Measured excess molar enthalpies, HE values for the various (i + j) mixtures as a function of mole fraction xi, of component (i) at T/K = 298.15. Also included are the various Hn (n = 0–2) parameters along with standard deviations r (HE). xi
HE/(J mol1)
xi
HE/(J mol1)
{1-Ethyl-3-methylimidazolium tetrafluoroborate (i) + pyridine (j)} 0.1025 147 0.4956 452 0.1335 188 0.5325 453 0.1727 232 0.5890 443 0.2121 280 0.6312 420 0.2654 328 0.6983 381 0.3078 364 0.7567 337 0.3587 405 0.8078 279 0.4112 424 0.8654 212 0.4632 448 0.9123 144 H(0) = 1797; H(1) = 129; H(2) = 171; r(HE) = 3 J mol1 {1-Ethyl-3-methylimidazolium tetrafluoroborate (i) + a-picoline (j)} 0.1132 109 0.5123 408 0.1578 148 0.5734 437 0.2087 194 0.6145 448 0.2467 225 0.6634 453 0.2976 266 0.7145 436 0.3245 286 0.7856 399 0.3789 326 0.8265 360 0.4235 356 0.8723 304 0.4876 395 0.9226 209 H(0) = 1600; H(1) = 1071; H(2) = 550; r(HE) = 3 J mol1 {1-Ethyl-3-methylimidazolium tetrafluoroborate (i) + b-picoline (j)} 0.1256 136 0.5223 369 0.1676 171 0.5990 376 0.2089 205 0.6345 372 0.2578 245 0.6890 360 0.2976 272 0.7356 339 0.3387 294 0.7909 298 0.3898 320 0.8479 244 0.4367 341 0.8890 197 0.4876 362 0.9109 165 H(0) = 1450; H(1) = 483; H(2) = 247; r(HE) = 2 J. mol1
FIGURE 1. Excess molar volumes, VE at 293.15 K: (I) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + pyridine (j)} Expt. ( ), Graph ( ); (II) {1-ethyl-3methylimidazolium tetrafluoroborate (i) + a-picoline (j)} Expt. ( ), Graph ( ); (III) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + b-picoline (j)} Expt. ( ), Graph ( ); (IV) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + cpicoline (j)} Expt. ( ), Graph ( ).
{1-Ethyl-3-methylimidazolium tetrafluoroborate (i) + c-picoline (j)} 0.1110 130 0.5267 436 0.1679 190 0.5908 444 0.2098 234 0.6150 443 0.2387 261 0.6786 423 0.2909 306 0.7234 408 0.3267 330 0.7945 352 0.3790 365 0.8346 303 0.4167 387 0.8890 226 0.4834 417 0.9267 163 H(0) = 1704; H(1) = 629; H(2) = 186; r(HE) = 3 J mol1 The uncertainty in mole fraction value is 1 104; the uncertainty in temperature is 0.01 K; the uncertainty in HE values is 1%; atmospheric pressure.
those of {[emim][BF4] (i) + Py (j)} mixture. This is indeed not true. It may be due to higher molar volumes (at T/K = 298.15) of a(98.96 106 m3 mol1) or b- (97.69 106 m3 mol1) or c(97.88 106 m3 mol1) picolines as compared to Py (80.80 106 m3 mol1) which restrict their approach between the clathrates of [emim][BF4] as compared to Py. Thus contribution to HE values due to factor (iv) will be more in pyridine as compared to picolines. The magnitude and sign of VE and jES data is a cumulative effect of contributions due to (i) breaking of self associated molecules (positive volume); (ii) break down of ionic interactions (positive volume); and (iii) packing effect and ion–dipole interactions between Py or isomeric picoline and [emim][BF4] molecules. The negative values of VE for the investigated mixtures suggest strong ion– dipole interactions (between [emim][BF4] and Py or isomeric picolines) and more closed packing of the constituent of mixtures in mixed state as compared to pure state. Further, temperature coefficient (oVE/oT) and (ojES /oT) is negative. This suggest that there may be a formation of associated species in {[emim][BF4] + Py or isomeric picoline} mixture with increase in temperature which
FIGURE 2. Excess molar volumes, VE at 298.15 K: (I) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + pyridine (j)} Expt. ( ), Graph ( ); (II) {1-ethyl-3methylimidazolium tetrafluoroborate (i) + a-picoline (j)} Expt. ( ), Graph ( ); (III) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + b-picoline (j)} Expt. ( ), Graph ( ); (IV) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + cpicoline (j)} Expt. ( ), Graph ( ).
results in contraction in volume of the mixture and hence negative VE or jES values.
4.1. Graph theory 4.1.1. Excess molar volumes Graph theory deals with the topology of the constituent of the mixtures. The topology of the pure (i)/(j) components changes with the addition of (i) to (j) or vice versa in (i + j) mixtures. Since excess molar volumes, VE reflects change in topology of the constituents of mixtures, it would therefore be worthwhile to analyze the observed VE data of (i + j) mixtures in terms of Graph theory to extract
S. Solanki et al. / J. Chem. Thermodynamics 56 (2013) 123–135
FIGURE 3. Excess molar volumes, VE at 303.15 K: (I) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + pyridine (j)} Expt. ( ), Graph ( ); (II) {1-ethyl-3methylimidazolium tetrafluoroborate (i) + a-picoline (j)} Expt. ( ), Graph ( ); (III) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + b-picoline (j)} Expt. ( ), Graph ( ); (IV) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + cpicoline (j)} Expt. ( ), Graph ( ).
FIGURE 4. Excess molar volumes, VE at 308.15 K: (I) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + pyridine (j)} Expt. ( ), Graph ( ); (II) {1-ethyl-3methylimidazolium tetrafluoroborate (i) + a-picoline (j)} Expt. ( ), Graph ( ); (III) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + b-picoline (j)} Expt. ( ), Graph ( ); (IV) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + cpicoline (j)} Expt. ( ), Graph ( ).
information about the state of components in pure and mixed state along with nature and extent of molecular interaction existing in mixtures. According to this theory [29] VE is given by
V E ¼ aij
hX
xi ð 3 n i Þ m
i1
X
xi ð3 nt Þ1 ;
ð7Þ
where aij is a constant characteristic of (i + j) mixture. The (3ni), (3ni)m (i = i or j) are the connectivity parameters of third degree of the components (i) and (j) in pure and mixed state and are defined [30] by 3
n¼
X m
ðdmm dmn dmo dmp Þ0:5 ;
ð8Þ
131
FIGURE 5. Excess isentropic compressibilities, jES at 293.15 K: (I) {1-ethyl-3methylimidazolium tetrafluoroborate (i) + pyridine (j)} Expt. ( ), Graph ( ); (II) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + a-picoline (j)} Expt. ( ), Graph ( ); (III) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + bpicoline (j)} Expt. ( ), Graph ( ); (IV) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + c-picoline (j)} Expt. ( ), Graph ( ).
FIGURE 6. Excess isentropic compressibilities, jES at 298.15 K: (I) {1-ethyl-3methylimidazolium tetrafluoroborate (i) + pyridine (j)} Expt. ( ), Graph ( ); (II) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + a-picoline (j)} Expt. ( ), Graph ( ); (III) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + bpicoline (j)} Expt. ( ), Graph ( ); (IV) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + c-picoline (j)} Expt. ( ), Graph ( ).
where dmm , etc. have the same significance as described elsewhere [31a,31b]. The (3ni), (3nj)m (i = i or j) parameters have been determined by fitting experimental VE data to equation (7) and only those values that best reproduced the experimental VE data have been retained. Such VE values are plotted in figures 1 to 4 and (3ni), (3nj)m (i = i or j) parameters at various mole fraction of (i), xi are listed in table 4. Examination of data in figures reveals that VE values compare well with their experimental values which in turn suggest that (3ni), (3nj)m (i = i or j) values can be utilized to extract information about the nature of i and j components in pure and mixed state. Various structures were proposed for [emim][BF4], Py or a- or b- or c-picoline and only those structures or combination of structures that yielded 3n/ value (calculated from structural con-
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FIGURE 7. Excess isentropic compressibilities, jES at 303.15 K: (I) {1-ethyl-3methylimidazolium tetrafluoroborate (i) + pyridine (j)} Expt. ( ), Graph ( ); (II) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + a-picoline (j)} Expt. ( ), Graph ( ); (III) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + bpicoline (j)} Expt. ( ), Graph ( ); (IV) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + c-picoline (j)} Expt. ( ), Graph ( ).
FIGURE 8. Excess Isentropic compressibilities, jES at 308.15 K: (I) {1-ethyl-3methylimidazolium tetrafluoroborate (i) + pyridine (j)} Expt. ( ), Graph ( ); (II) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + a-picoline (j)} Expt. ( ), Graph ( ); (III) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + bpicoline (j)} Expt. ( ), Graph ( ); (IV) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + c-picoline (j)} Expt. ( ), Graph ( ).
sideration via equation (8)) comparing well with 3n value (obtained via equation (7)) were taken to be representative structure of that component. For the investigated mixtures, It was assumed that [emim][BF4], Py or a-, b-, or c-picoline exist as molecular entities I, II–IV, V–VIII, IX–XI, and XII–XIII, respectively (scheme 1) and their 3n/ values were determined. The dmm , etc. values for the various vertices are shown in various molecular entities. For [BF4] anion in [emim][BF4], dmm value is taken as 1.5 and for p-electron cloud of aromatic ring of Py or picolines (dm (p) = 1). In evaluating 3n/ values for molecules entity I, it was assumed that [BF4] ion is positioned above the imidazolium ring of [emim][BF4] and [emim][BF4] is characterised by interactions between (i) hydrogen atom attached to C(2) atom of imidazolium ring and two florine atoms of [BF4]; and (ii)
FIGURE 9. Excess molar enthalpies, HE at 298.15 K: (I) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + pyridine (j)} Expt. ( ), Graph ( ); (II) {1-ethyl-3methylimidazolium tetrafluoroborate (i) + a-picoline (j)} Expt. ( ), Graph ( ); (III) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + b-picoline (j)} Expt. ( ), Graph ( ); (IV) {1-ethyl-3-methylimidazolium tetrafluoroborate (i) + cpicoline (j)} Expt. ( ), Graph ( ).
hydrogen atom of –CH3 group of imidazolium ring and florine atoms of [BF4]. The 3n/ values for these molecular entities were then calculated to be 1.639, 0.516, 0.706, 1.033, 0.814, 1.050, 1.184, 1.247, 0.788, 1.371, 1.226, 0.847, 0.933 respectively. The 3n values of 1.615 or 1.241, 0.901, 1.182, 1.312 and 1.513 for [emim][BF4], Py, a-, b-, c-picoline (table 4) suggest that [emim][BF4] exist as (molecular entity I; 3n/ = 1.639) monomer; pyridine (mixture of molecular entities III–IV; 3n/ = 0.869); a-picoline (molecular entity VII; 3 / n = 1.184); b-picoline (mixture of molecular entities X–XI; 3 / n = 1.298); c-picoline (molecular entity XII; 3n/ = 0.933) associated molecular entities. Our observations about the state of [emim][BF4] are consistent with earlier observations inferred from IR, Raman spectra and scaled quantum mechanics analysis of [emim][BF4] [32–34] which suggest that (i) [BF4] is positioned over the imidazolium ring and has short contacts not only with H–C(2), but also with a proton of the –CH3 group; and (ii) the ion pair formation strongly influences three antisymmetric B–F stretching vibrations of the anion, and out-of-plane and stretching vibrations of the H–C(2) moiety of the cation. Further, our observations about the state of Py or isomeric picolines are also in agreement with ab initio molecular orbital calculations [35] on the structural, energetic and electronic properties of Py, a-, b-, c-picoline suggesting that p-electron density at C2, C4, and C6 positions in pyridine is less than that in benzene. Thus either one, two or all three electron deficient carbon atoms in Py or isomeric picolines can involve in interaction with p-electron cloud of other molecule to yield associated molecular entity. The (3n/i)m values were then determined to extract information about the state of [emim][BF4] in {[emim][BF4] (i) + Py or a- or bor c-picoline (j)} mixtures. For this purpose it was assumed that studied mixtures may contain molecular entity XIV. In evaluating (3n/i)m value for this molecular entity it was assumed that nitrogen atom and electron deficient carbon atoms of Py or a- or b- or c-picoline are interacting with nitrogen atom (N-3) of imidazolium ring and florine atom of [BF4]. The (3n/i)m value for this molecular entity was then calculated to be 1.729. The (3ni)m values of 1.615 or 1.241 in {[emim][BF4] (i) + Py or a- or b- or c-picoline (j)} mixtures (table 4) suggest that these mixtures are characterized by the presence of molecular entity XIV. The existence of these molecular entities suggest that addition of [emim][BF4] to Py or a- or b- or c-picoline should change H–C(2) vibration of [emim]+ cation, B–F stretching
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S. Solanki et al. / J. Chem. Thermodynamics 56 (2013) 123–135 TABLE 4 The (3ni) = (3nj)m (i = i or j); aij , v=ij , etc. parameters for the various (i + j) mixtures at T/ K = (293.15, 298.15, 303.15, and 308.15). {1-Ethyl-3-methylimidazolium tetrafluoroborate (i) + pyridine (j)} T/K = 293.15 ( ni) = (3ni)m = 1.615; (3nj) = (3nj)m = 0.901 3 1 aij = 22.779 cm mol 3
v=ij ¼ 17:7 TPa1; v12 = 300.4 TPa1 T/K = 298.15
aij = 23.390 cm3 mol1 v=ij ¼ 15:6 TPa1; v12 = 339.1 TPa1
v=ij = 549 J mol-1; v12 = 1139 J mol1 T/K = 303.15
aij = 24.340 cm3 mol1 v=ij = 16.0 TPa1; v12 = 360.8 TPa1 T/K = 308.15
aij = 24.956 cm3 mol1 v=ij = 17.6 TPa1; v12 = 389.9 TPa1 {1-Ethyl-3-methylimidazolium tetrafluoroborate (i) + a-picoline (j)} T/K = 293.15 ( ni) = (3ni)m = 1.615; (3nj) = (3nj)m = 1.182 3 1 aij = 168.913 cm mol
of [BF4] anion, ring vibrations of Py or isomeric picolines. To substantiate this we analyzed IR spectral data of pure [emim][BF4], Py, b-picoline, and equimolar mixtures of {[emim][BF4] (i) + Py or bpicoline (j)}. It was observed that [emim][BF4], Py, and b-picoline in their pure state showed characteristic vibrations at 3124 cm1 (C–H vibrations), 522 cm1 (B–F stretching) and (1582, 1488, and 1440) cm1 (ring vibrations) [36] respectively. The IR data of {[emim][BF4] (i) + Py or b-picoline (j)} mixtures showed characteristic absorption at 3164 cm1, 3160 cm1 (C–H vibration), 533, 535 cm1 (B–F stretching); (1590, 1496, 1455; 1586, 1493, and 1450) cm1 (ring vibrations) respectively. The Shifting of H– C vibrations towards higher wave number suggest breakdown of interactions between hydrogen atom of imidazolium ring and florine atom of [BF4] anion. Further shifting of ring vibrations towards higher wave number indicates the interaction through nitrogen atom of Py or b-picoline ring [37]. The IR spectral data of investigated mixture suggest that the addition of i to j thus influence H–C vibrations of [emim], B–F stretching of [BF4], and ring vibration of Py or b-picoline. This lends additional support to the existence of molecular entity XIV.
3
v=ij = 75.5 TPa1; v12 = 263.9 TPa1 T/K = 298.15
aij = 171.169 cm3 mol1 v=ij = 93.4 TPa1; v12 = 235.4 TPa1
v=ij = -1055 J mol1; v12 = 365 J mol-1 T/K = 303.15
aij = 178.100 cm3 mol1 v=ij = 90.2 TPa1; v12 = 265.7 TPa1 T/K = 308.15
aij = 182.418 cm3 mol1 v=ij = 102.8 TPa1; v12 = 274.9 TPa1
4.1.2. Excess molar enthalpies and excess isentropic compressibilities Graph theory was next employed to predict HE and jES data of the {[emim][BF4] (i) + Py or a- or b- or c-picoline (j)} mixtures. For this purpose, it was assumed that investigated (i + j) mixtures formation may involve processes; (1) formation of unlike i–jn contacts; (2) unlike contact formation then weakens jn–jn interactions and ionic interactions which leads to the depolymerization of jn to form j monomers; (3) monomers of i and j undergo ion–dipole interactions to form 1:1 molecular complex. If vij ; vjj , and v12 are molar interactions and molar compressibilities interaction parameters for i–j, j–j contacts and specific interactions respectively, then change in thermodynamic properties, DXðX ¼ H or jS ) due to processes (1 to 3) is given [38–40] by
{1-Ethyl-3-methylimidazolium tetrafluoroborate (i) + b-picoline (j)} T/K = 293.15 ( ni) = (3ni)m = 1.615; (3nj) = (3nj)m = 1.312 aij = 331.712 cm3 mol1
xi xj vij v j DX 1 ðX ¼ H or jS Þ ¼ Pj ; i¼i xi v i
ð9Þ
v=ij = 64.3 TPa1; v12 = 214.0 TPa1
x2i xj vjj v j DX 2 ðX ¼ H or jS Þ ¼ P ; j i¼i xi v i
ð10Þ
xi x2j v12 v j DX 3 ðX ¼ H or jS Þ ¼ Pj ; i¼i xi v i
ð11Þ
3
T/K = 298.15
aij = 340.953 cm3 mol1 v=ij = 62.9 TPa1; v12 = 241.8 TPa1
v=ij = 811 J mol1; v12 = 209 J mol1 T/K = 303.15
aij = 350.235 cm3 mol1 v=ij = 75.2 TPa1; v12 = 247.0 TPa1 T/K = 308.15
aij = 368.771 cm3 mol1 v=ij = 85.2 TPa1; v12 = 250.1 TPa1 {1-Ethyl-3-methylimidazolium tetrafluoroborate (i) + c-picoline (j)} T/K = 293.15 (3ni) = (3ni)m = 1.241; (3nj) = (3nj)m = 1.513 aij = 417.782 cm3 mol1 = ij
1
v = 97.9 TPa ; v12 = 187.4 TPa
1
T/K = 298.15 3
1
aij = 418.369 cm mol v=ij = 110.7 TPa1; v12 = 180.2 TPa1
v=ij = 1393 J mol1; v12 = 377 J mol1 T/K = 303.15
aij = 433.438 cm3 mol1 v=ij = 132.5 TPa1; v12 = 163.9 TPa1 T/K = 308.15 aij = 451.568 cm3 mol1 = ij
1
v = 161.5 TPa ; v12 = 128.5 TPa
1
where v i is the molar volume of component (i). The overall change in thermodynamic properties, HE or jES for the investigated (i + j) mixtures due to processes (1 to 3) can, therefore, be expressed by equation (12)
HE or
jES ¼
3 h .X i X DX 1 ¼ x i xj v j xi v i ½vij þ xi vjj þ xj v12 :
ð12Þ
1¼1
Singh et al. [41] have suggested tion (12) reduces to
HE or
jES ¼
v j =v i ¼ 3 ni =3 nj . Consequently equa-
xi xj ð 3 n i = 3 n j Þ ½v þ xi vjj þ xj v12 : xi þ xj ð3 ni =3 nj Þ ij
ð13Þ
For the studied mixtures, it is reasonable to assume that vij ffi vjj ¼ v=ij equation (13) can therefore be expressed by
HE or
jES ¼
xi xj ð 3 n i = 3 n j Þ ½ð1 þ xi Þv=ij þ x=j v12 : xi þ xj ð3 ni =3 nj Þ
ð14Þ
Equation (14) contains two unknown parameters. These parameters were predicted by using HE and jES data at xi = 0.4 and 0.6 and were then utilized to determine HE and jES values of (i + j)
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S. Solanki et al. / J. Chem. Thermodynamics 56 (2013) 123–135
SCHEME 1. Connectivity parameters, 3n/ of the third degree for various molecular entities.
mixtures at other values of xi. Such jES and HE values are plotted in figures 5 to 9 and v=ij and v12 parameters are recorded in table 4. Examination of data in figures reveals that HE and jES values com-
pare well with their experimental values which in turn provide additional support to the various assumptions made in deriving equation (14).
S. Solanki et al. / J. Chem. Thermodynamics 56 (2013) 123–135
5. Conclusion The measured densities and speeds of sound data of the investigated mixtures are employed to predict excess molar volumes, VE and Excess isentropic compressibilities, jES . The topology of the molecules constituting the mixtures have been utilized to extract information about the state of components in pure and mixed state along with molecular entities existing in mixtures. The observed VE, HE, and jES have been analysed in terms of Graph theory. It has been observed that VE, HE, and jES values predicted by Graph theory compare well with experimental values. Even in those cases where the calculated and experimental values are not in agreement, they are of same sign and magnitude. Acknowledgement The Authors are thankful to the Head, Department of Chemistry and authorities of M.D. University, Rohtak, for providing research facilities. References [1] T. Welton, Chem. Rev. 99 (1999) 2071–2084. [2] P. Wasserscheid, T. Welton (Eds.), Ionic Liquid in Synthesis, Wiley-VCH, Weinheim, 2003. [3] C. Reichardt, Org. Process Res. Dev. 11 (2007) 105–113. [4] W. Marczak, S.P. Verevkin, A. Heintz, J. Solution Chem. 32 (2003) 519–526. [5] C.P. Fredlake, J.M. Crosthwaite, D.G. Hert, S.N.V.K. Aki, J.F. Brennecke, J. Chem. Eng. Data 49 (2004) 954–961. [6] M. Abareshi, E.K. Goharshadi, S.M. Zebarjad, J. Mol. Liq. 149 (2009) 66–73. [7] K.A. Kurnia, B. Ariwahjoedi, M.I.A. Mutalib, T. Murugesan, J. Solution Chem. 40 (2011) 470–480. [8] S. Zhang, X. Li, H. Chen, J. Wang, J. Zhang, M. Zhang, J. Chem. Eng. Data 49 (2004) 760–764. [9] M.R. Curras, M.F.C. Gomes, P. Husson, A.A.H. Padua, J. Garcia, J. Chem. Eng. Data 55 (2010) 5504–5512. [10] P. Navia, J. Troncoso, L. Romani, J. Chem. Eng. Data 52 (2007) 1369–1374. [11] A. Stoppa, O. Zech, W. Kunz, R. Buchner, J. Chem. Eng. Data 55 (2010) 1768– 1773. [12] J.S. Yadav, D. Sharma, V.K. Sharma, Thermochim. Acta 489 (2009) 45–52. [13] Neeti, S.K. Jangra, J.S. Yadav, Dimple, V.K. Sharma, J. Mol. Liq. 163 (2011) 36– 45.
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JCT 12-105