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The molar excess enthalpies and volumes of three 1-alkynes + 1-propanol and + 2-propanol mixtures at 298.15 K
313
Fluid Phase Equilibria, 91 (1993) 313-320 Elsevier Science Publishers B.V., Amsterdam
The molar excess enthalpies and volumes of three 1-alkynes + I-propanol and + 2-propanol mixtures at 298.15 K Trevor M. Letcher *, June D. Mercer-Chalmers
and Penny U. Govender
Department of Chemistry, University of Natal, King George V Avenue, Durban (South Africa)
Sarah E. Radloff Department of Mathematical Statistics, Rhodes University, Grahamstown (South Africa) (Received January
11, 1993; accepted in final form March 30, 1993)
ABSTRACT Letcher, T.M., Mercer-Chalmers, J.D. and Radloff, S.E., 1993. The molar excess enthalpies and volumes of three 1-alkynes + 1-propanol and + 2-propanol mixtures at 298.15 K. Fluid Phase Equilibria, 91: 3 13-320. The molar excess enthalpies, H&, and volumes, VE, of three I-alkyne + I-propanol and 1-alkyne + 2-propanol mixtures have been measured at 298.15 K. The alkynes include 1-hexyne, I-heptyne and 1-octyne. These measurements are compared with the Hg and VE values for the binary mixtures: I-alkyne + methanol, I-alkyne + ethanol and as n-alkane + an alkanol. Keywords: experiments, data, excess enthalpies, excess volumes, 1-alkynes, alcohols. INTRODUCTION
In a previous paper by Letcher and co-workers (1990), the molar excess enthalpies HE and molar excess volumes VE at 298.15 K for binary mixtures of three I-alkynes with methanol and ethanol are reported and discussed. In this work the above Hk and Vz measurements were extended to include the alkanols, 1-propanol and 2-propanol. The results are discussed in terms of specific interactions between the triple bonds in the alkyne molecules and the hydrogen bonds between the alkanol molecules. No Hz and VE measurements have been reported in the literature for any 1-alkyne - alkanol mixtures. * Corresponding
author.
0378-3812/93/$06.00 0 1993 - Elsevier Science Publishers B.V. All rights reserved
314
TM. Letcher et al. /Fluid Phase Equilibria 91 (1993) 313-320
EXPERIMENTAL
Materials The suppliers, purification and properties of the 1-alkynes have been described by Letcher and co-workers (1990). The propanols were supplied by Aldrich Chemical Company and were dried repeatedly using the method of Lund and Bjerrum described by Vogel ( 1978). The water impurity in the alkanols was determined by a Karl Fischer titration to be less than 0.01 mol%. The alkanols were kept dry before use. The densities of the 1-propanol and 2-propanol at 298.15 K was found to be 0.79982 and 0.78152 g cmp3, respectively. Procedure The excess volumes were measured using a (Paar DMA 601) vibrating tube density meter and the excess enthalpies were measured using an LKB 2107 calorimeter. The methods have been described by Letcher and coworkers ( 1990). The accuracy of the Hi and Vi measurements was estimated to be 4 J mol-’ and 0.004 cm3 mol-‘, respectively.
RESULTS
The HE and Vk results are given in Tables 1 and 2 respectively together with the deviations AH: and AVE. These were calculated from the smoothing equation AH:=
HE-x(1
-x)
c A,(1 -2x)‘/[l
+k(l
r=O
-2x)]
(1)
and AV:=
V:-x(1
-x)
c B,(1 -2x)’ r=O
where x refers to the mole fraction. The values of the coefficients A, and B, together with the standard deviation Q are given in Tables 3 and 4, respectively. The standard deviation, 6, was determined from the equation o2 = C [XE(exp) - _XE(calc)12/(p - 12- 1) where p is the number of measurements or V.
in the set and X refers to either H
0.4526 0.5032 0.5658 0.6318 0.7015 0.7525 0.4940 0.4969 0.6214 0.6532 0.6998 0.7050 0.3706 0.4265
+ (1 - x)CH,CH,CH20H 95.6 - 19.5 278.0 0.5 322.9 5.4 470.9 6.1 654.8 1.2 760.8 3.5
+ (1 - x)CH,CH,CH,OH 192.2 10.8 359.6 6.0 399.4 0.4 615.6 -9.1 726.3 -7.5 746.2 -0.8
+ (1 - x)CH,CH(OH)CH, 198.9 - 10.7 451.3 -0.3
xl-C,H,, 0.0652 0.1543 0.1753 0.2558 0.3668 0.4370
xl-CsH,, 0.0887 0.1762 0.2001 0.3283 0.3997 0.4091
xl-C,H,, 0.0637 0.1457
X
0.3826 0.4458 0.5463 0.5756 0.6538 0.6928
AH: (Jmol-‘)
943.8 1019.4
850.7 861.2 957.2 965.0 976.2 975.8
775.2 839.7 891.9 931.2 941.0 929.2
658.2 740.4 849.6 869.2 914.7 921.7
1.2 -2.4
-2.5 4.9 2.5 -1.1 6.3 6.5
-2.9 0.7 -6.0 -5.0 -3.1 5.6
-5.4 -5.1 1.1 -1.6 5.5 7.5
AH: (J mol-‘)
0.6578 0.7098
0.7553 0.8302 0.8596 0.8664 0.9502
0.7715 0.7874 0.8363 0.8721 0.9502
0.7359 0.7569 0.8045 0.8642 0.9012
X
at 298 K and the deviations
(J mol-‘)
H.5
+ (1 - x)C,H,OH]
+ (1 - x)CH,CH,CH,OH 154.6 -4.6 225.8 -0.1 276.3 4.0 290.1 -2.5 379.4 2.7 467.4 5.6
(J mol-I)
HEi
for [xl -C,H,_,
xl-C,H,, 0.0827 0.1182 0.1434 0.1545 0.2016 0.2513
X
Molar excess enthalpies coefficients in Table 3
TABLE 1
1127.8 1196.5
950.8 857.2 800.7 789.6 454.2
916.3 898.6 822.4 741.8 450.7
904.4 892.0 851.5 745.6 648.7
(J mol-‘)
HEi
AHE calculated
-4.3 -1.6
0.6 -8.2 -5.4 0.0 5.8
7.2 4.7 -2.9 -7.4 2.3
-1.6 -3.8 -2.2 -4.8 4.8
$I%-1)
from eqn. (1) and the
2 ul
-1.2 2.8 5.0
590.8 785.9 864.2
-x)CH,CH(OH)CH, 342.9 -0.6 406.7 -8.6 768.6 -0.6 972.1 2.7 8.5 1007.4
-x)CH,CH(OH)CH, 284.2 -7.0 594.8 -2.6 0.5 798.0 4.8 926.2 1013.9 4.3
0.1992 0.283 1 0.3220
xl-C,H,,+(l 0.0970 0.1200 0.2559 0.3635 0.3833
xl-C*H,,+(l 0.0749 0.1714 0.2511 0.3123 0.3656
AH:
(J mol-‘)
HE
(J molk’)
X
TABLE 1 (continued)
0.4724 0.5017 0.5532 0.6098 0.6768
0.4736 0.4805 0.5802 0.6115 0.6534
0.5062 0.5997 0.6280
X
1129.8 1158.7 1177.8 1189.0 1159.0
1107.6 1109.6 1160.5 1163.2 1152.7 3.8 3.2 -3.1 0.5 -7.1
3.4 -0.7 -3.6 -3.7 -6.0
2.3 -0.4 -1.6
(J mol-‘)
(J mol-‘) 1104.2 1140.9 1138.7
AH:
HITi
0.7514 0.8037 0.8412 0.8482 0.9135
0.7084 0.7816 0.8025 0.8593 0.9462
0.7538 0.8685 0.9102
X
1089.7 1004.5 898.2 885.8 610.2
1119.6 1027.7 986.5 836.0 407.7
1047.6 796.8 608.9
(J mol-‘)
HfTl
E
- 1.4 7.9 -1.8 7.0 -7.3
-4.3 3.0 4.1 9.7 -11.2
0.4 12.7 -9.7
f?k-1)
Vtf,
0.3495 0.472 1 0.5744
0.3277 0.4429 0.5386
0.2954 0.3899 0.5284 0.6151 0.3668 0.5033
+ (1 - x)CH,CH,CH,OH -0.036 -4 - 0.047 2 -0.055 2 - 0.052 0
+ (1 - x)CH,CH,CH,OH -0.013 2 - 0.025 0 - 0.026 0 -0.017 2
+ (1 - x)CH,CH(OH)CH, -0.012 -5 -0.010 -5 0.117 2 0.055 6
+ (1 - x)CH,CH(OH)CH, 0.007 2 0.025 -3
xl-C,H,, 0.0509 0.0997 0.1811 0.2497
xl-&H,, 0.0400 0.0899 0.1657 0.2248
xl-&H,, 0.0560 0.0779 0.1129 0.2067
xl-C,H,, 0.0356 0.1008
X
0.5097 0.6332 0.7128
lo3 Al’: (cm3 mol-r)
+ (1 - x)CH,CH,CH,OH - 0.054 2 - 0.083 -3 - 0.094 3 - 0.092 -1
( cm3 mol-‘)
xl-C,H,, 0.0637 0.1123 0.2544 0.3968
X
Molar excess volumes for [x 1-C, H, _ 2 + ( 1 - x)C,H,OH] Table 4
TABLE 2
0.188 0.262
0.102 0.155 0.209 0.226
- 0.005 0.039 0.061
-0.034 0.001 0.028
- 0.085 - 0.073 - 0.060
VE (Gr3 mol-I)
-7
-2 -4
-7 6 1
1 1
3
0
0
-2
0 0 0
lo3 AV: ( cm3 mol- I)
0.7319 0.8506
0.7737 0.8970 0.8425
0.6815 0.7830 0.8906
0.7378 0.8037 0.8771
0.7558 0.8260 0.9009
X
0.258 0.195
0.203 0.110 0.151
0.089 0.096 0.080
0.059 0.065 0.060
- 0.050 - 0.033 -0.015
(cm3 mol-‘)
v:
-5
-3 -4
9
3
0 0
0
-2 -2
-1
-1
1 0
lo3 AVE (cm3 mol-‘)
at 298.15 K and the deviations calculated from eqn. (2) and the coefficients of
xl-C8H,, 0.0939 0.1678 0.2377 0.3422
0.1889 0.2523
X
1O’AV:
3 2
( cm3 mol- ‘)
+ (1 - x)CH,CH(OH)CH, 0.036 2 0.076 -2 0.125 -2 0.205 4
0.084 0.125
VE (cl3 mol-‘)
TABLE 2 (continued)
0.4548 0.5555 0.6969
0.5840
X Vi
0.266 0.296 0.290
0.282
( cm3 mol- ‘)
-3 3
0
4
lo3 AV: ( cm3 mol- ‘)
0.7899 0.8561 0.9322
0.9205
X CA
0.236 0.174 0.094
0.126
(cm3 mol-‘)
-3 2
0
3
lo3 AV: (cm3 mol-‘)
319
TM. L.etcher et al. /Fluid Phase Equilibria 91 (1993) 313-320 TABLE 3
Coefficients of eqn. (1) for [XC,,H, _ 2 + ( 1 - x)C, H,, + IOH] at 298.15 K and the standard deviation a(Hfi) Mixture
ACI
A,
k
4
MC3 (J mol- ‘)
3222 3342 3438 4388 4503 4617
xl-C,H,,+ (1 -x)CH,CH,CH,OH xl-C,H,, + (1 - x)CH,CH,CH,OH xl-C,H,,+(l -x)CH,CH,CH,OH xl-&H,, + (1 - x)CH,CH(OH)CH, xl-C,H,, + (1 - x)CH,CH(OH)CH, xl-CsH,,+(l -x)CH,CH(OH)CH,
511 702 647 1682 1254 1488
-242 -845 - 347 -82 497 698
0.79 0.87 0.81 0.74 0.60 0.61
4.8 7.3 6.5 6.3 6.7 5.7
TABLE 4 Coefficients of eqn. (2) for [xCyHs_ deviation a( VE)
2 + (1 - x)C, Hz=+, OH] at 298.15 K and the standard
Mixture
B0
B,
B,
4
w:) (cm3 mol-‘)
l-C,H,, + CH,CH&H,OH l-r&H,, + CH,CH,CH,OH 1-C,H,, + CH,CH$H,OH l-CgHu,+CH3CH(OH)CH3 I-C,H,, + CH,CH(OH)CH, 1-CsH,, + CH,CH(OH)CH,
-0.339 0.030 0.197 0.819 1.031 1.140
-0.122 -0.532 -0.549 -0.644 - 0.663 -0.687
-0.239 - 0.007 0.101 -0.314 -0.089 -0.324
-0.469 -0.282 -0.212 -0.188 - 0.247 -0.061
0.002 0.002 0.004 0.005 0.005 0.003
DISCUSSION
The Hi for a I-alkyne + I-propanol or 2-propanol mixture are all positive with a maximum at about 0.7 mole fraction of 1-alkyne. The large positive value is most likely a reflection of the breaking of the hydrogen bonds between the alkanol molecules as a result of the mixing process. Comparing these results with those published previously by Letcher and co-workers ( 1990) for a I-alkyne with methanol or ethanol, it can be seen that HE (maximum) increases with increasing carbon number. For example Hk (maximum) for mixtures of I-hexyne with methanol, ethanol, lpropanol and 2-propanol are 642, 775, 922 and 1142 J mol-’ respectively. For each l-alkyne, Hk (maximum) for mixtures containing l-propanol are less positive than HE (maximum) for mixtures containing 2-propanol. For example Hz (maximum) for I-heptyne with 1-propanol and 2-propanol are 943 and 1165 J mol-’ respectively.
320
TM.
Letcher et al. / Fluid Phase Equilibria 91 (1993) 313-320
For each alkanol, the Hi (maximum) value increases only slightly with increasing I-alkene carbon number. For example, HL (maximum) for mixtures containing 1-propanol with 1-hexyne, I-heptyne and I-octyne are 922, 945 and 980 J mol-’ respectively. The triple bond in the I-alkyne has a major effect on the Hi (maximum) value. This can be seen by comparing the HE (maximum) for l-heptyne + I-propanol (945 J mol-‘) with the HE (maximum) for heptane + lpropanol (640 J mol-‘) determined by Ragaini and co-workers (1968). The effect is probably due to the combined positive effects of the dissociation of alkanols (breakdown of hydrogen bonds) and the dissociation of I-alkynes (breakdown of lI . . . II interactions). There is no evidence of II . . . H or OH interactions between I-alkynes and alkanols from the HE results. The volume changes Vk on mixing a 1-alkyne with an alkanol are more complicated in that some of the results are negative while most results show a positive excess molar volume. These results reflect a positive effect of the breakdown of the hydrogen bonds between the alkanol molecules on mixing, a positive effect of the breakdown of l7 . . . II interactions between the I-alkyne molecule, a negative effect of the association between an alkanol and a I-alkyne and an unpredictable effect due to molecular packing. ACKNOWLEDGEMENTS
The authors wish to thank the FRD (South Africa) and Natal University Research Committee for financial support. REFERENCES Letcher, T.M., Schoonbaert, F.E.Z. and Bean, B., 1990. The molar excess enthalpies and volumes of I-alkyne + methanol and + ethanol mixtures at 298.15 K. Fluid Phase Equilibria, 61: 111-119. Ragaini, V., Santi, R. and Car& S., 1968. The molar excess enthalpies for an alkano1 + heptane. Atti. Accad. Naz. Lincei, Cl. Sci. Fis., Mat. Natur., Rend., 45: 540-549. Vogel, 1978. Text book of Practical Organic Chemistry, revised by B. Furniss, A. J. Hannaford, V. Rogers, P. W. G. Smith and A. R. Tatchell(4th edn.), Longmans, London, p. 268.
Fluid Phase Equilibria, 91 (1993) 313-320 Elsevier Science Publishers B.V., Amsterdam
The molar excess enthalpies and volumes of three 1-alkynes + I-propanol and + 2-propanol mixtures at 298.15 K Trevor M. Letcher *, June D. Mercer-Chalmers
and Penny U. Govender
Department of Chemistry, University of Natal, King George V Avenue, Durban (South Africa)
Sarah E. Radloff Department of Mathematical Statistics, Rhodes University, Grahamstown (South Africa) (Received January
11, 1993; accepted in final form March 30, 1993)
ABSTRACT Letcher, T.M., Mercer-Chalmers, J.D. and Radloff, S.E., 1993. The molar excess enthalpies and volumes of three 1-alkynes + 1-propanol and + 2-propanol mixtures at 298.15 K. Fluid Phase Equilibria, 91: 3 13-320. The molar excess enthalpies, H&, and volumes, VE, of three I-alkyne + I-propanol and 1-alkyne + 2-propanol mixtures have been measured at 298.15 K. The alkynes include 1-hexyne, I-heptyne and 1-octyne. These measurements are compared with the Hg and VE values for the binary mixtures: I-alkyne + methanol, I-alkyne + ethanol and as n-alkane + an alkanol. Keywords: experiments, data, excess enthalpies, excess volumes, 1-alkynes, alcohols. INTRODUCTION
In a previous paper by Letcher and co-workers (1990), the molar excess enthalpies HE and molar excess volumes VE at 298.15 K for binary mixtures of three I-alkynes with methanol and ethanol are reported and discussed. In this work the above Hk and Vz measurements were extended to include the alkanols, 1-propanol and 2-propanol. The results are discussed in terms of specific interactions between the triple bonds in the alkyne molecules and the hydrogen bonds between the alkanol molecules. No Hz and VE measurements have been reported in the literature for any 1-alkyne - alkanol mixtures. * Corresponding
author.
0378-3812/93/$06.00 0 1993 - Elsevier Science Publishers B.V. All rights reserved
314
TM. Letcher et al. /Fluid Phase Equilibria 91 (1993) 313-320
EXPERIMENTAL
Materials The suppliers, purification and properties of the 1-alkynes have been described by Letcher and co-workers (1990). The propanols were supplied by Aldrich Chemical Company and were dried repeatedly using the method of Lund and Bjerrum described by Vogel ( 1978). The water impurity in the alkanols was determined by a Karl Fischer titration to be less than 0.01 mol%. The alkanols were kept dry before use. The densities of the 1-propanol and 2-propanol at 298.15 K was found to be 0.79982 and 0.78152 g cmp3, respectively. Procedure The excess volumes were measured using a (Paar DMA 601) vibrating tube density meter and the excess enthalpies were measured using an LKB 2107 calorimeter. The methods have been described by Letcher and coworkers ( 1990). The accuracy of the Hi and Vi measurements was estimated to be 4 J mol-’ and 0.004 cm3 mol-‘, respectively.
RESULTS
The HE and Vk results are given in Tables 1 and 2 respectively together with the deviations AH: and AVE. These were calculated from the smoothing equation AH:=
HE-x(1
-x)
c A,(1 -2x)‘/[l
+k(l
r=O
-2x)]
(1)
and AV:=
V:-x(1
-x)
c B,(1 -2x)’ r=O
where x refers to the mole fraction. The values of the coefficients A, and B, together with the standard deviation Q are given in Tables 3 and 4, respectively. The standard deviation, 6, was determined from the equation o2 = C [XE(exp) - _XE(calc)12/(p - 12- 1) where p is the number of measurements or V.
in the set and X refers to either H
0.4526 0.5032 0.5658 0.6318 0.7015 0.7525 0.4940 0.4969 0.6214 0.6532 0.6998 0.7050 0.3706 0.4265
+ (1 - x)CH,CH,CH20H 95.6 - 19.5 278.0 0.5 322.9 5.4 470.9 6.1 654.8 1.2 760.8 3.5
+ (1 - x)CH,CH,CH,OH 192.2 10.8 359.6 6.0 399.4 0.4 615.6 -9.1 726.3 -7.5 746.2 -0.8
+ (1 - x)CH,CH(OH)CH, 198.9 - 10.7 451.3 -0.3
xl-C,H,, 0.0652 0.1543 0.1753 0.2558 0.3668 0.4370
xl-CsH,, 0.0887 0.1762 0.2001 0.3283 0.3997 0.4091
xl-C,H,, 0.0637 0.1457
X
0.3826 0.4458 0.5463 0.5756 0.6538 0.6928
AH: (Jmol-‘)
943.8 1019.4
850.7 861.2 957.2 965.0 976.2 975.8
775.2 839.7 891.9 931.2 941.0 929.2
658.2 740.4 849.6 869.2 914.7 921.7
1.2 -2.4
-2.5 4.9 2.5 -1.1 6.3 6.5
-2.9 0.7 -6.0 -5.0 -3.1 5.6
-5.4 -5.1 1.1 -1.6 5.5 7.5
AH: (J mol-‘)
0.6578 0.7098
0.7553 0.8302 0.8596 0.8664 0.9502
0.7715 0.7874 0.8363 0.8721 0.9502
0.7359 0.7569 0.8045 0.8642 0.9012
X
at 298 K and the deviations
(J mol-‘)
H.5
+ (1 - x)C,H,OH]
+ (1 - x)CH,CH,CH,OH 154.6 -4.6 225.8 -0.1 276.3 4.0 290.1 -2.5 379.4 2.7 467.4 5.6
(J mol-I)
HEi
for [xl -C,H,_,
xl-C,H,, 0.0827 0.1182 0.1434 0.1545 0.2016 0.2513
X
Molar excess enthalpies coefficients in Table 3
TABLE 1
1127.8 1196.5
950.8 857.2 800.7 789.6 454.2
916.3 898.6 822.4 741.8 450.7
904.4 892.0 851.5 745.6 648.7
(J mol-‘)
HEi
AHE calculated
-4.3 -1.6
0.6 -8.2 -5.4 0.0 5.8
7.2 4.7 -2.9 -7.4 2.3
-1.6 -3.8 -2.2 -4.8 4.8
$I%-1)
from eqn. (1) and the
2 ul
-1.2 2.8 5.0
590.8 785.9 864.2
-x)CH,CH(OH)CH, 342.9 -0.6 406.7 -8.6 768.6 -0.6 972.1 2.7 8.5 1007.4
-x)CH,CH(OH)CH, 284.2 -7.0 594.8 -2.6 0.5 798.0 4.8 926.2 1013.9 4.3
0.1992 0.283 1 0.3220
xl-C,H,,+(l 0.0970 0.1200 0.2559 0.3635 0.3833
xl-C*H,,+(l 0.0749 0.1714 0.2511 0.3123 0.3656
AH:
(J mol-‘)
HE
(J molk’)
X
TABLE 1 (continued)
0.4724 0.5017 0.5532 0.6098 0.6768
0.4736 0.4805 0.5802 0.6115 0.6534
0.5062 0.5997 0.6280
X
1129.8 1158.7 1177.8 1189.0 1159.0
1107.6 1109.6 1160.5 1163.2 1152.7 3.8 3.2 -3.1 0.5 -7.1
3.4 -0.7 -3.6 -3.7 -6.0
2.3 -0.4 -1.6
(J mol-‘)
(J mol-‘) 1104.2 1140.9 1138.7
AH:
HITi
0.7514 0.8037 0.8412 0.8482 0.9135
0.7084 0.7816 0.8025 0.8593 0.9462
0.7538 0.8685 0.9102
X
1089.7 1004.5 898.2 885.8 610.2
1119.6 1027.7 986.5 836.0 407.7
1047.6 796.8 608.9
(J mol-‘)
HfTl
E
- 1.4 7.9 -1.8 7.0 -7.3
-4.3 3.0 4.1 9.7 -11.2
0.4 12.7 -9.7
f?k-1)
Vtf,
0.3495 0.472 1 0.5744
0.3277 0.4429 0.5386
0.2954 0.3899 0.5284 0.6151 0.3668 0.5033
+ (1 - x)CH,CH,CH,OH -0.036 -4 - 0.047 2 -0.055 2 - 0.052 0
+ (1 - x)CH,CH,CH,OH -0.013 2 - 0.025 0 - 0.026 0 -0.017 2
+ (1 - x)CH,CH(OH)CH, -0.012 -5 -0.010 -5 0.117 2 0.055 6
+ (1 - x)CH,CH(OH)CH, 0.007 2 0.025 -3
xl-C,H,, 0.0509 0.0997 0.1811 0.2497
xl-&H,, 0.0400 0.0899 0.1657 0.2248
xl-&H,, 0.0560 0.0779 0.1129 0.2067
xl-C,H,, 0.0356 0.1008
X
0.5097 0.6332 0.7128
lo3 Al’: (cm3 mol-r)
+ (1 - x)CH,CH,CH,OH - 0.054 2 - 0.083 -3 - 0.094 3 - 0.092 -1
( cm3 mol-‘)
xl-C,H,, 0.0637 0.1123 0.2544 0.3968
X
Molar excess volumes for [x 1-C, H, _ 2 + ( 1 - x)C,H,OH] Table 4
TABLE 2
0.188 0.262
0.102 0.155 0.209 0.226
- 0.005 0.039 0.061
-0.034 0.001 0.028
- 0.085 - 0.073 - 0.060
VE (Gr3 mol-I)
-7
-2 -4
-7 6 1
1 1
3
0
0
-2
0 0 0
lo3 AV: ( cm3 mol- I)
0.7319 0.8506
0.7737 0.8970 0.8425
0.6815 0.7830 0.8906
0.7378 0.8037 0.8771
0.7558 0.8260 0.9009
X
0.258 0.195
0.203 0.110 0.151
0.089 0.096 0.080
0.059 0.065 0.060
- 0.050 - 0.033 -0.015
(cm3 mol-‘)
v:
-5
-3 -4
9
3
0 0
0
-2 -2
-1
-1
1 0
lo3 AVE (cm3 mol-‘)
at 298.15 K and the deviations calculated from eqn. (2) and the coefficients of
xl-C8H,, 0.0939 0.1678 0.2377 0.3422
0.1889 0.2523
X
1O’AV:
3 2
( cm3 mol- ‘)
+ (1 - x)CH,CH(OH)CH, 0.036 2 0.076 -2 0.125 -2 0.205 4
0.084 0.125
VE (cl3 mol-‘)
TABLE 2 (continued)
0.4548 0.5555 0.6969
0.5840
X Vi
0.266 0.296 0.290
0.282
( cm3 mol- ‘)
-3 3
0
4
lo3 AV: ( cm3 mol- ‘)
0.7899 0.8561 0.9322
0.9205
X CA
0.236 0.174 0.094
0.126
(cm3 mol-‘)
-3 2
0
3
lo3 AV: (cm3 mol-‘)
319
TM. L.etcher et al. /Fluid Phase Equilibria 91 (1993) 313-320 TABLE 3
Coefficients of eqn. (1) for [XC,,H, _ 2 + ( 1 - x)C, H,, + IOH] at 298.15 K and the standard deviation a(Hfi) Mixture
ACI
A,
k
4
MC3 (J mol- ‘)
3222 3342 3438 4388 4503 4617
xl-C,H,,+ (1 -x)CH,CH,CH,OH xl-C,H,, + (1 - x)CH,CH,CH,OH xl-C,H,,+(l -x)CH,CH,CH,OH xl-&H,, + (1 - x)CH,CH(OH)CH, xl-C,H,, + (1 - x)CH,CH(OH)CH, xl-CsH,,+(l -x)CH,CH(OH)CH,
511 702 647 1682 1254 1488
-242 -845 - 347 -82 497 698
0.79 0.87 0.81 0.74 0.60 0.61
4.8 7.3 6.5 6.3 6.7 5.7
TABLE 4 Coefficients of eqn. (2) for [xCyHs_ deviation a( VE)
2 + (1 - x)C, Hz=+, OH] at 298.15 K and the standard
Mixture
B0
B,
B,
4
w:) (cm3 mol-‘)
l-C,H,, + CH,CH&H,OH l-r&H,, + CH,CH,CH,OH 1-C,H,, + CH,CH$H,OH l-CgHu,+CH3CH(OH)CH3 I-C,H,, + CH,CH(OH)CH, 1-CsH,, + CH,CH(OH)CH,
-0.339 0.030 0.197 0.819 1.031 1.140
-0.122 -0.532 -0.549 -0.644 - 0.663 -0.687
-0.239 - 0.007 0.101 -0.314 -0.089 -0.324
-0.469 -0.282 -0.212 -0.188 - 0.247 -0.061
0.002 0.002 0.004 0.005 0.005 0.003
DISCUSSION
The Hi for a I-alkyne + I-propanol or 2-propanol mixture are all positive with a maximum at about 0.7 mole fraction of 1-alkyne. The large positive value is most likely a reflection of the breaking of the hydrogen bonds between the alkanol molecules as a result of the mixing process. Comparing these results with those published previously by Letcher and co-workers ( 1990) for a I-alkyne with methanol or ethanol, it can be seen that HE (maximum) increases with increasing carbon number. For example Hk (maximum) for mixtures of I-hexyne with methanol, ethanol, lpropanol and 2-propanol are 642, 775, 922 and 1142 J mol-’ respectively. For each l-alkyne, Hk (maximum) for mixtures containing l-propanol are less positive than HE (maximum) for mixtures containing 2-propanol. For example Hz (maximum) for I-heptyne with 1-propanol and 2-propanol are 943 and 1165 J mol-’ respectively.
320
TM.
Letcher et al. / Fluid Phase Equilibria 91 (1993) 313-320
For each alkanol, the Hi (maximum) value increases only slightly with increasing I-alkene carbon number. For example, HL (maximum) for mixtures containing 1-propanol with 1-hexyne, I-heptyne and I-octyne are 922, 945 and 980 J mol-’ respectively. The triple bond in the I-alkyne has a major effect on the Hi (maximum) value. This can be seen by comparing the HE (maximum) for l-heptyne + I-propanol (945 J mol-‘) with the HE (maximum) for heptane + lpropanol (640 J mol-‘) determined by Ragaini and co-workers (1968). The effect is probably due to the combined positive effects of the dissociation of alkanols (breakdown of hydrogen bonds) and the dissociation of I-alkynes (breakdown of lI . . . II interactions). There is no evidence of II . . . H or OH interactions between I-alkynes and alkanols from the HE results. The volume changes Vk on mixing a 1-alkyne with an alkanol are more complicated in that some of the results are negative while most results show a positive excess molar volume. These results reflect a positive effect of the breakdown of the hydrogen bonds between the alkanol molecules on mixing, a positive effect of the breakdown of l7 . . . II interactions between the I-alkyne molecule, a negative effect of the association between an alkanol and a I-alkyne and an unpredictable effect due to molecular packing. ACKNOWLEDGEMENTS
The authors wish to thank the FRD (South Africa) and Natal University Research Committee for financial support. REFERENCES Letcher, T.M., Schoonbaert, F.E.Z. and Bean, B., 1990. The molar excess enthalpies and volumes of I-alkyne + methanol and + ethanol mixtures at 298.15 K. Fluid Phase Equilibria, 61: 111-119. Ragaini, V., Santi, R. and Car& S., 1968. The molar excess enthalpies for an alkano1 + heptane. Atti. Accad. Naz. Lincei, Cl. Sci. Fis., Mat. Natur., Rend., 45: 540-549. Vogel, 1978. Text book of Practical Organic Chemistry, revised by B. Furniss, A. J. Hannaford, V. Rogers, P. W. G. Smith and A. R. Tatchell(4th edn.), Longmans, London, p. 268.