Thermodynamic, ultrasonic and FT-IR studies on binary liquid mixtures of anisaldehyde and alkoxyethanols at different temperatures

Journal of Molecular Liquids 178 (2013) 99–112

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Thermodynamic, ultrasonic and FT-IR studies on binary liquid mixtures of anisaldehyde and alkoxyethanols at different temperatures Zareena Begum, P.B. Sandhya Sri, D.B. Karuna Kumar, C. Rambabu ⁎ Department of Chemistry, Acharya Nagarjuna University — Dr. M.R. Appa Rao Campus, Nuzvid-521201, Krishna District, Andhra Pradesh, India

a r t i c l e

i n f o

Article history: Received 3 November 2012 Accepted 19 November 2012 Available online 11 December 2012 Keywords: Alkoxyethanol Anisaldehyde Ultrasonic speed Excess molar volume Redlich–Kister polynomial FT-IR

a b s t r a c t The experimental density, viscosity, and ultrasonic speeds of anisaldehyde (AA) and alkoxyethanols namely 2-methoxy ethanol (MOE), 2-ethoxy ethanol (EOE) and 2-butoxy ethanol (BOE) have been measured over the full range of compositions at atmospheric pressure and at different temperatures (303.15, 308.15, 313.15 and 318.15 K). From these experimental values the molar volume (Vm), adiabatic compressibility (βad) and intermolecular free length (Lf), are computed and their excess properties along with deviation in viscosity (Δη) are fitted to Redlich–Kister type equation, a multi parametric nonlinear regression analysis technique to derive the binary coefficients and to estimate the standard deviation between experimental and calculated data. The experimental data of viscosity is also used to test the applicability of empirical relations of Grunberg–Nissan, Katti–Chaudhri, Heric–Brewer and Hind et al. for the systems studied. Further, FT IR analysis of these binary mixtures at different concentrations, confirms the presence of hydrogen bonding, and supported the results as observed in thermodynamic analysis with respect to forces of association/dispersion between unlike molecules. The interaction of AA with alkoxyethanol is found to decrease with increase in alkyl chain length of the alkoxy group. © 2012 Elsevier B.V. All rights reserved.

1. Introduction Chemical thermodynamics is used to predict whether a mixture of reactants has a spontaneous tendency to change into products, to predict the composition of the reaction mixture at equilibrium, and to predict how that composition will be modified by changing the conditions. Physico-chemical and thermodynamic investigations play an important role in understanding the nature and extent of the patterns of molecular aggregation that exist in binary liquid mixtures due to their sensitivities to variations in composition and the molecular structure of the pure components [1,2]. The experimental data of excess thermodynamic properties of liquid mixtures provide useful information about molecular interactions and can be used to test thermodynamic models [3–5]. Interactions of the type: ion–ion, ion–solvent, and solvent–solvent within the liquid system are understood by the interpretation of data obtained from thermo-chemical, electrochemical, biochemical, and kinetic studies. The physical properties, such as density, viscosity, surface tension, refractive index, dielectric constant, molar polarization, group frequency shift in IR spectra, etc. give important information about the overall changes resulting from various interactions that occur when liquids are mixed together.

⁎ Corresponding author. Fax: +91 8656 235200. E-mail address: [email protected] (C. Rambabu). 0167-7322/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.molliq.2012.11.016

Alkoxyethanols are a very interesting class of substances from a practical point of view, as oxygenated compounds are increasingly used as additives to gasoline due to their octane enhancing and pollution-reducing properties [6,7]. They have wide use as monomers in the production of polymers and emulsion formulations. Alkoxyethanols are considered as constituted of two different functional subgroups viz., an ether subgroup (R-O-), which includes an oxygen atom attached to a methylene group, and a primary alcohol sub group (\OH). From a theoretical point of view, mixtures containing alkoxy alcohols are very important, not only because of their self association but also due to the strong intra-molecular effects which is produced by the presence of \O and \OH groups in the same molecule [8]. In particular, the formation of the intra-molecular H-bonds leads to enhanced dipole–dipole interactions in solutions containing oxy-ethanols and alkanes relative to those present in mixtures with homomorphic alkanols [9]. There has been a recent upsurge of interest in the study of thermodynamic properties of binary liquid mixtures [10,11]. Different spectroscopic techniques like IR and NMR have been used to investigate the existence of intra-molecular hydrogen bonds [12], even in vapor phase. For molecules of the type CH3\(CH2) n\O\(CH2) n\OH, 5 or 6 or 7 membered rings are formed (for n = 2, 3 and 4 respectively). It is reported that, alkoxyethanols with two ether groups and n =1 form 5-membered rings similar to those previously cited; but can also form 8-membered rings of quite different properties [13]. P-anisaldehyde (CH3OC6H4CHO) — an aromatic pale clear liquid, with a methoxy group in para-position of the benzene ring. Chemically

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it is 4-methoxy-benzaldehyde, which is soluble in alcohol and ether and insoluble in water.

Detailed research has shown that research work has been done on the binary mixtures of anisaldehyde with a variety of compounds. Less amount of work is done with anisaldehyde as common compound. It's been studied with acetonitrile [14]; cresols [15] halobenzenes [16] benzenes [17]. It is evident from the existing available data that no work is yet done on the binary mixtures of alkoxyethanols and anisaldehyde. The present work reports the density (ρ) and viscosity (η) for binary mixtures of anisaldehyde (AA) with 2-methoxyethanol (MOE), 2-ethoxyethanol (EOE), and 2-butoxyethanol (BOE) over the entire range of composition at 303.15 K, 313.15 K, and 323.15 K, and the derived thermodynamic properties of the above mentioned binary mixtures. It is also aimed to study the molecular interactions between AA and alkoxyethanols, giving a stress on dipole induced interactions and hydrogen bonding. The infrared spectroscopic studies (FT-IR) further support/reveal the existence of specific interactions through their bond stretching vibrations/change in intensity in specific wave lengths. Further, the empirical relations of viscosity like Katti–Chaudhry, Grunberg–Nissan Heric Brewer and Hind et al. are tested for the applicability on the experimental viscosity data of all systems studied.

2. Experimental 2.1. Materials and method 2-methoxyethanol (MOE); 2-ethoxyethanol (EOE) and 2butoxyethanol (BOE) and anisaldehyde (AA) were purchased from S.D Fine Chemicals India and were purified as described in the literature [18]. The pure chemicals were stored over activated 4 Å molecular sieves to reduce water content before use. The chemicals after purification were 99.8% pure, and their purity was ascertained by GLC and also by comparing experimental values of density, viscosity, and ultrasound velocity with those reported in the literature when available, as presented in Table 1. The binary mixtures are prepared gravimetrically using an electronic balance (Shimadzu AY120) with an uncertainty of ±1 × 10−7 kg and stored in airtight bottles. The uncertainty on mole fraction is estimated to be 1 × 10 −4. It is ensured that the mixtures are properly mixed and

the measurement of the required parameters was done within one day of preparation. The viscosity, η, of the pure liquids and liquid mixtures is determined using an Ubbelohde suspended-level viscometer. The viscometer is suspended in a thermostatted water bath in which the temperature is maintained constant to ±0.01 K. Three sets of readings for the flow time are taken by using a Racer stop watch that can register time to ±0.01 s, and the arithmetic mean is taken for the calculation of the viscosity. Because the flow times are greater than 200 s and the capillary diameter is 0.55 mm, which is much less than the tube length of 100 mm, both kinetic energy and tube end corrections are negligible. The viscometer is calibrated with triple distilled water and dry cyclohexane. It is estimated using the following formula: η=ηw ¼ ρ t=ρw t w :

ð1Þ

The estimated uncertainty in the viscosity measurements is found to be less than 1%. The densities, ρ, of pure liquids and their mixtures are determined using a 10−5 m 3 double-arm pycnometer, and the values from triplicate replication at each temperature are reproducible within 2 × 10– 1 kg m 3. The pycnometer is calibrated using conductivity water with 995.61 kg m−3 as its density at 303.15 K. The position of the liquid levels, in the two arms of the pycnometer (which is made sure that it is air bubble-free), is recorded with the help of a traveling microscope that could be read to 0.01 mm, and the uncertainty in the measurement of density is found to be 2 parts in 104 parts. The reproducibility in mole fractions was within ±0.0002. Temperature control for the measurement of viscosity and density is achieved by using a microprocessor assisted circulating water bath, (supplied by Mac, New Delhi) regulated to ±0.01 K, using a proportional temperature controller. Adequate precautions were taken to minimize evaporation losses during the actual measurements. Ultrasonic velocity of sound (u) were determined by a multifrequency ultrasonic Interferometer (Mittal Enterprise, New Delhi, M-81) working at 1 MHz, The uncertainty of the ultrasonic velocity measurements was 0.8 m s −1. IR measurements for all the three binary mixtures of AA over the entire composition range are recorded through Nicolet nexus 670 spectrometer (Germany), using KBr pellet in the region (400 to 4000) cm −1 with 4.0 cm −1 resolution. The uncertainty in the measurement of wave number is within ± 0.1 cm −1. 2.2. Calculations Following are the equations adopted for calculating the parameters from the measured parameters mentioned above.   2 −1 Adiabatic compressibility βad ¼ ρ U

ð2Þ

Table 1 Comparison of density ρ, viscosity η and ultrasonic velocity U, of the pure liquids with literature data at 303.15 K. Compound

Experimental ρ × 10−3 kg/m3

Literature ρ × 10−3 kg/m3

Experimental η/m·pas

Literature η/m.pas

Experimental u/m·s−1

Literature u/m·s−1

Anisaldehyde M.O.E E.O.E B.O.E

1.1204 0.9527 0.9186 0.8921

1.1200a 0.9558b 0.9212b 0.8923b

3.5783 1.5476 1.6315 2.4031

3.5783a 1.544d 1.643b 2.408b

1543.0 1354.0 1314.4 1321.4

1542.0a 1359.2c 1319.2c 1322.0c

a b c d

[38]. [39]. [40]. [41].

Z. Begum et al. / Journal of Molecular Liquids 178 (2013) 99–112

Molar volume V ¼ ðX 1 M 1 þ X 2 M 2 Þ=ρ Intermolecular free length Lf ¼ KT =U ρ

1=2

ð3Þ

2.3. Theoretical considerations for viscosity

ð4Þ

There are several semi-empirical relations used to correlate the viscosity of binary liquid mixtures, which help us to know the strength of molecular interactions. The dynamic viscosities have been calculated by the following empirical relations. The Grunberg–Nissan proposed the empirical relation as

where K is the temperature dependent Jacobson constant and T is the absolute temperature. The excess properties such as Δβad, V E, Δη Ε and LfE have been calculated using the equation E

Y ¼ Y mix −ðX 1 Y 1 þ X 2 Y 2 Þ:

ð5Þ

These excess functions were fitted to Redlich–Kister type polynomial equation E

Y cal ¼ X 1 X 2 ∑A J−1 ðX 2 −X 1 Þ

J−1

:

ð6Þ

The values of coefficient a j-1 evaluated by the method of least squares with all points weighed equally with the standard deviations are calculated as     E E E 1=2 σ Y ¼ Y ob −Y cal =ðm−nÞ

101

ð7Þ

where ‘m’ is the number of experimental data points and n is the number of coefficients considered (n = 5 in the present calculation).

ln η ¼ x1 ln η1 þ x2 ln η2 þ x1 x2 G12

ð8Þ

where G12 is an interaction parameter, which is a function of viscosity of component liquids 1 and 2 and temperature. Katti and Choudhri equation for the dynamic viscosity of the liquid mixture is

lnðη V Þ ¼ x1 ln η1 V 1 þ x2 ln η2 V 2 þ x1 x2 W vis =RT

ð9Þ

where Wvis is an interaction term. Heric and Brewer derived the following equation to calculate the viscosity of binary liquid mixtures ln η ¼ x1 ln η1 þ x2 ln η2 þ x1 ln M 1 þ x2 ln M2 − lnðx1 M 1 þ x2 M2 Þx1 x2 Δ12

ð10Þ

where Δ12 is the interaction term and other symbols have their usual meaning.

Table 2 Ultrasonic velocities (u/m·sec−1), densities (ρ/Kg·m−3) and viscosities (η/m·Pas) of binary mixtures of Anisaldehyde with oxyalcohols at different temeratures. (303.15, 308.15, 313.15 and 318.15 K). X1

303.15 K u/m·s

−1

308.15 K ρ/g·cm

−3

η/m·Pas

u/m·s

−1

313.15 K ρ/g·cm

−3

η/m·Pas

u/m·s

−1

318.15 K ρ/g·cm

−3

η/m·Pas

u/m·s−1

ρ/g·cm−3

η/m·Pas

AA + MOE 0.0000 0.0753 0.1549 0.2391 0.3283 0.4231 0.5238 0.6311 0.7457 0.8684 1.0000

1354.0 1369.5 1387.0 1406.3 1427.0 1448.6 1470.6 1492.2 1512.4 1529.8 1543.0

0.9527 0.9664 0.9808 0.9957 1.0113 1.0275 1.0445 1.0622 1.0808 1.1002 1.1204

1.5476 1.5021 1.5178 1.5672 1.6564 1.7927 1.9844 2.2418 2.5773 3.0058 3.5783

1344.0 1355.8 1369.9 1385.8 1403.5 1422.6 1442.6 1462.9 1482.8 1501.3 1517.0

0.9503 0.9649 0.9799 0.9953 1.0111 1.0274 1.0441 1.0611 1.0785 1.0961 1.1140

1.4895 1.4628 1.4884 1.5374 1.6139 1.7229 1.8700 2.0622 2.3079 2.6172 3.0347

1335.0 1345.3 1358.0 1372.8 1389.6 1408.1 1428.0 1448.7 1469.7 1490.2 1509.0

0.9456 0.9606 0.9760 0.9917 1.0077 1.0240 1.0404 1.0570 1.0737 1.0903 1.1067

1.2176 1.2137 1.2580 1.3205 1.4043 1.5132 1.6513 1.8237 2.0367 2.2979 2.6487

1312.0 1320.8 1332.2 1346.0 1362.0 1380.3 1400.5 1422.2 1445.2 1468.7 1492.0

0.9420 0.9575 0.9732 0.9891 1.0051 1.0213 1.0374 1.0535 1.0693 1.0847 1.0995

1.1284 1.1292 1.1754 1.2356 1.3120 1.4076 1.5253 1.6690 1.8433 2.0538 2.3402

AA + EOE 0.0000 0.0825 0.1683 0.2576 0.3506 0.4474 0.5484 0.6539 0.7641 0.8793 1.0000

1314.4 1332.7 1351.9 1372.0 1393.0 1415.0 1438.0 1462.3 1487.8 1514.7 1543.0

0.9186 0.9351 0.9522 0.9701 0.9888 1.0083 1.0287 1.0500 1.0724 1.0958 1.1204

1.5720 1.5211 1.5341 1.5861 1.6821 1.8281 2.0301 2.2941 2.6291 3.0441 3.5783

1298.0 1313.4 1329.9 1347.6 1366.7 1387.2 1409.3 1433.1 1458.9 1486.8 1517.0

0.9160 0.9330 0.9505 0.9687 0.9874 1.0067 1.0268 1.0475 1.0689 1.0910 1.1140

1.4870 1.4591 1.4831 1.5351 1.6181 1.7351 1.8911 2.0901 2.3381 2.6411 3.0347

1272.0 1286.8 1303.1 1321.1 1340.8 1362.5 1386.4 1412.8 1441.8 1473.7 1509.0

0.91030 0.92770 0.94557 0.96392 0.98276 1.00208 1.02192 1.04230 1.06322 1.08467 1.10670

1.3360 1.3301 1.3711 1.4311 1.5121 1.6171 1.7491 1.9121 2.1081 2.3421 2.6487

1248.0 1261.7 1277.3 1294.7 1314.3 1336.3 1360.9 1388.5 1419.2 1453.6 1492.0

0.9067 0.9243 0.9423 0.9607 0.9795 0.9986 1.0180 1.0379 1.0581 1.0786 1.0995

1.2500 1.2511 1.2941 1.3511 1.4231 1.5131 1.6231 1.7551 1.9111 2.0961 2.3402

AA + BOE 0.0000 0.1088 0.2154 0.3201 0.4227 0.5234 0.6223 0.7193 0.8146 0.9081 1.0000

1321.4 1332.9 1347.2 1364.1 1383.4 1405.0 1428.8 1454.6 1482.3 1511.8 1543.0

0.8921 0.9100 0.9292 0.9496 0.9712 0.9938 1.0174 1.0419 1.0673 1.0935 1.1204

2.4030 2.1972 2.0893 2.0549 2.0900 2.1908 2.3536 2.5749 2.8515 3.1801 3.5783

1274.0 1284.7 1299.0 1316.5 1337.2 1360.8 1387.2 1416.1 1447.5 1481.2 1517.0

0.8870 0.9060 0.9260 0.9469 0.9687 0.9912 1.0145 1.0385 1.0631 1.0883 1.1140

2.2880 2.1068 2.0061 1.9626 1.9732 2.0349 2.1448 2.3002 2.4987 2.7376 3.0347

1266.0 1274.7 1287.5 1304.0 1324.1 1347.6 1374.3 1403.9 1436.4 1471.4 1509.0

0.8822 0.9016 0.9219 0.9429 0.9645 0.9869 1.0098 1.0333 1.0573 1.0818 1.1067

2.1190 1.9841 1.9122 1.8810 1.8884 1.9321 2.0102 2.1206 2.2618 2.4317 2.6487

1243.0 1250.7 1262.8 1279.2 1299.5 1323.4 1351.0 1381.7 1415.6 1452.4 1492.0

0.8796 0.8996 0.9201 0.9412 0.9627 0.9846 1.0069 1.0296 1.0526 1.0759 1.0995

1.9370 1.8360 1.7861 1.7656 1.7729 1.8065 1.8649 1.9467 2.0507 2.1755 2.3402

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Z. Begum et al. / Journal of Molecular Liquids 178 (2013) 99–112

Table 3 E Molar volume (Vm), adiabatic compressibility(βad), intermolecular free length (Lf), excess molar volume (vm ), excess adiabatic compressibility(βadE), excess intermolecular free length (LfE), and excess viscosity (ηE) for the binary systems of all three oxy-ethanols at different temperatures. X1

Vm/cm3·mol−1

VE/cm3·mol−1

Lf/10−10 m

LfE/10−10 m

βad/10−12 m2·N−1

βad E/10−12 m2N−1

ηE/mPa·s

AA + MOE/303.15 K 0.0000 79.773 0.0753 82.870 0.1549 86.137 0.2391 89.592 0.3283 93.259 0.4231 97.161 0.5238 101.332 0.6311 105.805 0.7457 110.625 0.8684 115.841 1.0000 121.519

0.0000 0.2591 0.4782 0.6530 0.7779 0.8438 0.8465 0.7752 0.6189 0.3649 0.0000

0.4744 0.4657 0.4565 0.4468 0.4369 0.4270 0.4172 0.4077 0.3988 0.3907 0.3839

0.0000 −0.0026 −0.0052 −0.0077 −0.0099 −0.0116 −0.0123 −0.0120 −0.0101 −0.0063 0.0000

57.254 55.169 52.998 50.782 48.562 46.375 44.268 42.280 40.454 38.838 37.488

0.0000 −0.7412 −1.4698 −2.1323 −2.6751 −3.0454 −3.1792 −3.0157 −2.4860 −1.5119 0.0000

0.0000 −0.1835 −0.3161 −0.4263 −0.5094 −0.5596 −0.5707 −0.5344 −0.4410 −0.2786 0.0000

308.15 K 0.0000 0.0753 0.1549 0.2391 0.3283 0.4231 0.5238 0.6311 0.7457 0.8684 1.0000

79.975 83.005 86.215 89.629 93.272 97.173 101.375 105.920 110.861 116.266 122.217

0.0000 0.1588 0.2853 0.3787 0.4375 0.4578 0.4419 0.3874 0.2941 0.1633 0.0000

0.4786 0.4708 0.4624 0.4535 0.4443 0.4348 0.4254 0.4161 0.4072 0.3989 0.3916

0.0000 −0.0019 −0.0039 −0.0060 −0.0078 −0.0093 −0.0101 −0.0099 −0.0084 −0.0053 0.0000

58.256 56.379 54.385 52.314 50.204 48.093 46.023 44.035 42.171 40.477 39.007

0.0000 −0.5686 −1.1573 −1.7156 −2.1918 −2.5350 −2.6825 −2.5749 −2.1447 −1.3162 0.0000

0.0000 −0.1318 −0.2190 −0.2914 −0.3460 −0.3789 −0.3861 −0.3622 −0.3007 −0.1939 0.0000

313.15 K 0.0000 0.0753 0.1549 0.2391 0.3283 0.4231 0.5238 0.6311 0.7457 0.8684 1.0000

80.372 83.371 86.555 89.952 93.590 97.502 101.733 106.332 111.359 116.891 123.023

0.0000 0.0989 0.1702 0.2150 0.2342 0.2270 0.1996 0.1547 0.0987 0.0416 0.0000

0.4830 0.4755 0.4674 0.4586 0.4495 0.4400 0.4305 0.4210 0.4117 0.4030 0.3950

0.0000 −0.0015 −0.0032 −0.0050 −0.0067 −0.0081 −0.0088 −0.0088 −0.0075 −0.0048 0.0000

59.338 57.516 55.560 53.506 51.392 49.255 47.137 45.078 43.118 41.303 39.682

0.0000 −0.4851 −1.0070 −1.5163 −1.9619 −2.2934 −2.4483 −2.3676 −1.9845 −1.2244 0.0000

0.0000 −0.1012 −0.1614 −0.2113 −0.2489 −0.2715 −0.2764 −0.2598 −0.2173 −0.1436 0.0000

318.15 K 0.0000 0.0753 0.1549 0.2391 0.3283 0.4231 0.5238 0.6311 0.7457 0.8684 1.0000

80.679 83.646 86.808 90.191 93.828 97.756 102.024 106.687 111.814 117.491 123.829

0.0000 0.0337 0.0449 0.0369 0.0131 −0.0241 −0.0641 −0.0988 −0.1145 −0.0915 0.0000

0.4924 0.4851 0.4771 0.4684 0.4592 0.4495 0.4396 0.4295 0.4196 0.4099 0.4008

0.0000 −0.0010 −0.0024 −0.0039 −0.0053 −0.0066 −0.0074 −0.0074 −0.0065 −0.0041 0.0000

61.671 59.868 57.901 55.809 53.627 51.392 49.146 46.928 44.778 42.738 40.857

0.0000 −0.3883 −0.8354 −1.2921 −1.7075 −2.0304 −2.1979 −2.1500 −1.8195 −1.1316 0.0000

0.0000 −0.0816 −0.1238 −0.1589 −0.1852 −0.2010 −0.2044 −0.1926 −0.1627 −0.1110 0.0000

AA + EOE303.15 0.0000 0.0823 0.1679 0.2571 0.3499 0.4467 0.5477 0.6532 0.7636 0.8790 1.0000 308.15 K 0.0000 0.0823 0.1679 0.2571 0.3499 0.4467 0.5477 0.6532

K 98.1047 100.4292 102.7579 105.0906 107.4270 109.7699 112.1153 114.4624 116.8127 119.1662 121.5191

0.0000 0.3970 0.7211 0.9670 1.1297 1.2060 1.1863 1.0627 0.8298 0.4797 0.0000

0.49771 0.48652 0.47528 0.46399 0.45266 0.44129 0.42989 0.41843 0.40695 0.39544 0.38390

0.0000 −0.0018 −0.0033 −0.0045 −0.0052 −0.0056 −0.0055 −0.0049 −0.0039 −0.0022 0.0000

63.0106 60.2094 57.4596 54.7624 52.1195 49.5357 47.0079 44.5369 42.1261 39.7772 37.4882

0.0000 −0.7003 −1.2649 −1.6876 −1.9610 −2.0742 −2.0238 −1.8018 −1.3968 −0.7987 0.0000

0.0000 −0.2161 −0.3749 −0.5017 −0.5919 −0.6401 −0.6408 −0.5885 −0.4749 −0.2915 0.0000

98.3886 100.6564 102.9430 105.2503 107.5807 109.9395 112.3261 114.7427

0.0000 0.3063 0.5527 0.7364 0.8546 0.9068 0.8863 0.7885

0.50472 0.49425 0.48359 0.47274 0.46169 0.45048 0.43907 0.42747

0.0000 −0.0012 −0.0021 −0.0029 −0.0034 −0.0037 −0.0037 −0.0034

64.7999 62.1381 59.4859 56.8461 54.2218 51.6196 49.0385 46.4817

0.0000 −0.5386 −0.9824 −1.3236 −1.5533 −1.6588 −1.6343 −1.4696

0.0000 −0.1553 −0.2639 −0.3498 −0.4105 −0.4433 −0.4436 −0.4079

Z. Begum et al. / Journal of Molecular Liquids 178 (2013) 99–112

103

Table 3 (continued) X1

Vm/cm3·mol−1

308.15 K 0.7636 0.8790 1.0000

117.1946 119.6858 122.2172

313.15 K 0.0000 0.0823 0.1679 0.2571 0.3499 0.4467 0.5477 0.6532 0.7636 0.8790 1.0000

VE/cm3·mol−1

Lf/10−10 m

LfE/10−10 m

βad/10−12 m2·N−1

βad E/10−12 m2N−1

ηE/mPa·s

0.6116 0.3514 0.0000

0.41569 0.40374 0.39160

−0.0027 −0.0015 0.0000

43.9551 41.4632 39.0071

−1.1506 −0.6642 0.0000

−0.3307 −0.2064 0.0000

99.0003 101.2279 103.4829 105.7688 108.0894 110.4518 112.8572 115.3100 117.8180 120.3878 123.0234

0.0000 0.2500 0.4483 0.5932 0.6835 0.7205 0.6991 0.6171 0.4748 0.2707 0.0000

0.51664 0.50588 0.49481 0.48342 0.47171 0.45969 0.44736 0.43470 0.42175 0.40850 0.39497

0.0000 −0.0007 −0.0014 −0.0019 −0.0024 −0.0026 −0.0026 −0.0025 −0.0020 −0.0012 0.0000

67.8955 65.0976 62.2791 59.4445 56.5993 53.7527 50.9066 48.0673 45.2450 42.4481 39.6818

0.0000 −0.4755 −0.8783 −1.1985 −1.4244 −1.5399 −1.5359 −1.3982 −1.1079 −0.6470 0.0000

0.0000 −0.1140 −0.1854 −0.2424 −0.2832 −0.3053 −0.3059 −0.2814 −0.2303 −0.1478 0.0000

318.15 K 0.0000 0.0823 0.1679 0.2571 0.3499 0.4467 0.5477 0.6532 0.7636 0.8790 1.0000

99.3934 101.5979 103.8395 106.1230 108.4539 110.8409 113.2871 115.7993 118.3877 121.0618 123.8290

0.0000 0.1930 0.3425 0.4483 0.5106 0.5322 0.5101 0.4439 0.3364 0.1890 0.0000

0.52762 0.51687 0.50570 0.49408 0.48202 0.46954 0.45662 0.44326 0.42949 0.41532 0.40078

0.0000 −0.0003 −0.0006 −0.0009 −0.0012 −0.0014 −0.0015 −0.0015 −0.0013 −0.0008 0.0000

70.8121 67.9571 65.0499 62.0958 59.1021 56.0808 53.0363 49.9782 46.9208 43.8773 40.8571

0.0000 −0.3891 −0.7317 −1.0162 −1.2288 −1.3505 −1.3691 −1.2664 −1.0190 −0.6037 0.0000

0.0000 −0.0887 −0.1390 −0.1792 −0.2084 −0.2239 −0.2241 −0.2071 −0.1714 −0.1122 0.0000

AA + BOE/303.15 0.0000 0.0896 0.1812 0.2751 0.3712 0.4696 0.5705 0.6738 0.7798 0.8885 1.0000

K 132.463 131.990 131.317 130.467 129.470 128.347 127.117 125.806 124.424 122.992 121.519

0.0000 0.7095 1.1984 1.4884 1.6128 1.5916 1.4453 1.1981 0.8632 0.4609 0.0000

0.5024 0.4931 0.4828 0.4717 0.4599 0.4477 0.4351 0.4223 0.4094 0.3966 0.3839

0.0000 0.0035 0.0058 0.0070 0.0074 0.0071 0.0062 0.0050 0.0034 0.0018 0.0000

64.1975 61.8504 59.2965 56.5931 53.8038 50.9751 48.1481 45.3626 42.6424 40.0137 37.4882

0.0000 0.5384 0.8189 0.9002 0.8473 0.7077 0.5239 0.3367 0.1713 0.0548 0.0000

0.0000 −0.3328 −0.5654 −0.7223 −0.8076 −0.8252 −0.7786 −0.6718 −0.5075 −0.2895 0.0000

308.15 K 0.0000 0.0896 0.1812 0.2751 0.3712 0.4696 0.5705 0.6738 0.7798 0.8885 1.0000

133.224 132.572 131.772 130.841 129.805 128.680 127.479 126.222 124.917 123.581 122.217

0.0000 0.5366 0.9050 1.1214 1.2135 1.1962 1.0847 0.8986 0.6467 0.3454 0.0000

0.5047 0.4942 0.4836 0.4727 0.4617 0.4505 0.4391 0.4275 0.4157 0.4037 0.3916

0.0000 0.0043 0.0071 0.0086 0.0090 0.0085 0.0075 0.0059 0.0041 0.0021 0.0000

69.4604 66.8708 64.0017 60.9289 57.7350 54.4827 51.2274 48.0210 44.8961 41.8863 39.0071

0.0000 0.7003 1.0630 1.1652 1.0913 0.9051 0.6634 0.4196 0.2077 0.0622 0.0000

0.0000 −0.2619 −0.4418 −0.5631 −0.6290 −0.6426 −0.6065 −0.5238 −0.3967 −0.2280 0.0000

313.15 K 0.0000 0.0896 0.1812 0.2751 0.3712 0.4696 0.5705 0.6738 0.7798 0.8885 1.0000

133.949 133.216 132.363 131.403 130.360 129.244 128.070 126.852 125.598 124.321 123.023

0.0000 0.4471 0.7536 0.9325 1.0085 0.9935 0.9002 0.7456 0.5363 0.2865 0.0000

0.5166 0.5059 0.4948 0.4834 0.4717 0.4597 0.4474 0.4347 0.4217 0.4085 0.3950

0.0000 0.0050 0.0083 0.0100 0.0105 0.0101 0.0088 0.0070 0.0049 0.0025 0.0000

70.7238 68.2555 65.4433 62.3711 59.1316 55.7975 52.4341 49.1027 45.8434 42.6963 39.6818

0.0000 0.8853 1.3673 1.5315 1.4722 1.2635 0.9720 0.6605 0.3704 0.1430 0.0000

0.0000 −0.1922 −0.3202 −0.4066 −0.4535 −0.4631 −0.4375 −0.3786 −0.2881 −0.1680 0.0000

318.15 K 0.0000 0.0896 0.1812 0.2751 0.3712

134.344 133.517 132.612 131.638 130.612

0.0000 0.3089 0.5204 0.6421 0.6939

0.5276 0.5169 0.5057 0.4941 0.4820

0.0000 0.0055 0.0091 0.0110 0.0116

73.5813 71.0624 68.1483 64.9322 61.5175

0.0000 1.0164 1.5750 1.7708 1.7086

0.0000 −0.1446 −0.2373 −0.2998 −0.3338 (continued on next page)

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Table 3 (continued) X1

Vm/cm3·mol−1

318.15 K 0.4696 0.5705 0.6738 0.7798 0.8885 1.0000

129.543 128.437 127.308 126.158 124.998 123.829

VE/cm3·mol−1 0.6829 0.6176 0.5113 0.3672 0.1963 0.0000

Lf/10−10 m

LfE/10−10 m

0.4695 0.4566 0.4433 0.4295 0.4153 0.4008

0.0111 0.0097 0.0078 0.0054 0.0027 0.0000

Hind et al. gave an expression to determine the viscosity of the liquid mixtures as 2

2

η ¼ x1 η1 þ x2 η2 þ 2x1 x2 H12 :

ð11Þ

3. Results and discussions The experimental values of Ultrasonic velocity, density and viscosity of three binary mixtures at temperatures 303.15, 308.15, 313.15 and 318.15 K are presented in Table 2. From these values, it is observed that, in all the systems, ultrasonic speed, density and viscosity increased non-linearly with mole fraction of AA. This non-linear variation is a deviation from ideal behavior which suggests the presence of intermolecular interactions between the component molecules of the mixtures, however the strength of interaction is well reflected in the excess parameters like excess molar volume (VE), and deviation in viscosity (Δη) etc, as these parameters are found to be more sensitive towards intermolecular interactions in the liquid mixtures [19]. Larger dispersion with temperature at lower values of mole fractions of AA has been observed. However this dispersion gradually decreased with mole fraction of AA and is almost zero at X1 = 1. The dominance of AA over oxy-ethanols in breaking the intermolecular associations, followed by new hydrogen bond formation (oxygen atom of anisaldehyde and the hydrogen atom of alkoxyethanol) can be inferred. This is further supported by decrease of βad and Lf values in MOE and EOE; whereas, in BOE, a reverse trend is observed (positive) in those indicating very less or no associations. From the thermodynamic point of view — the ultrasonic velocity, adiabatic compressibility, deviation in adiabatic compressibility, free length along with the other data like excess molar volume, viscosity, are strongly affected by the changes of concentration and temperature, besides the type of bonding present between the molecules of the constituent liquids. Hydrogen bonding causes considerable influence on these parameters, because of the fact that specific interactions between the molecules are controlled mainly by hydrogen bond that binds the molecules together and therefore the density variation with temperature is less at higher values of X1. Computed values of the parameters analyzed/and their excess values are given in Table 3. 3.1. Excess molar volumes The magnitude and the sign of VE can be qualitatively examined by considering the physical, structural and chemical contributions [20]. Fig. 1a, b, and c illustrates the excess molar volumes (VE) for the binary systems of AA with MOE, EOE and BOE at 303.15 K. Similar trends were found at higher temperatures. The sign of the excess volume (VE) of a system depends on the relative magnitude of expansion/contraction on mixing of two liquids. As the factors causing expansion dominate the factors causing contraction, positive (VE) values are noted. Conversely when the contractive factors dominate the expansive factors, negative signs are observed. Mixing of AA with alkoxyethanol induces a decrease in the molecular order in the latter resulting in an expansion in volume and hence positive (VE) values. Sometimes the behavior of liquid mixtures may also depend on the orientation of molecules within

βad/10−12 m2·N−1 57.9870 54.4155 50.8728 47.4054 44.0589 40.8571

βad E/10−12 m2N−1 1.4728 1.1398 0.7806 0.4434 0.1748 0.0000

ηE/mPa·s −0.3408 −0.3223 −0.2797 −0.2143 −0.1274 0.0000

the liquid mixture to favor the bond formation, the alkoxyethanols have been well known to exist in relative energetically favorable rotameric conformers [21,22] (anti and gauche)and this property may also play a vital role in volume changes. The self-association of alkoxyethanols via intramolecular H-bonds and the strong dipole dipole interactions lead to values of the self-association enthalpy and of the adjustable parameter of the physical contribution to H E and VE that are higher than those of the homomorphic 1-alkanols [23]. One of the two pairs of electrons that make up a carbon–oxygen double bond is even more easily pulled towards the oxygen, which makes the carbon–oxygen double bond very highly polar.

This polarity with a dipole moment of 3.7855 [24] further tries to pull the hydrogen from oxyethanol molecules (protonators), which are already self-associated. We have speculated the possible non-involvement of methoxy (OCH3) group in heteromolecular associations, as there is a possibility of it already interacting with the π electrons of the aromatic residues, whereby the oxygen atom of the methoxy group gets stabilized. We can thus consider only the action of carbonyl group in bond formations. The addition of anisaldehyde into the alcohols first breaks the intermolecular hydrogen bond within alkoxyethanols, and then forms a new hydrogen bond (intermolecular) between heteromolecules, leading to complex formation. It is assumed that the hydrogen atom of the aldehyde group has a tendency to form both intra, and inter-molecular hydrogen bonding [25] but, because of polarized C_O\H bond. The newly formed inter molecular hydrogen bond (C_O…H) has more effect than the intramolecular hydrogen bonding causing the breakage of self associates. This is evident from the IR graphs, which are discussed in separate section of this paper. The graphical representation in Fig. 1a, b and c and values from Table 3 show that excess molar volumes at 303.15 k for the binary E mixtures increase in their values gradually. For AA+ MOE (Vm = 3 −1 3 E 0.8465 cm mol at X1 = 0.5238,) AA +EOE (Vm =1.1863 cm mol−1 at x1 =0.5477) and for AA+BOE it is found to be 1.5916 cm3.mol−1 at X1 =0.4696. The observed higher positive values of (VE) over the entire range of mole fraction in AA +BOE system may be attributed to the dominance of molecular dissociation over association. In addition to this the intestinal accommodation of MOE and EOE molecules into the voids of AA whose molar volume (121.5191 cm 3 mol − 1) is greater than the two alkoxyethanols under study at 303.15 K.(Vm = 79.7733 cm 3 mol − 1 for MOE and 98.1047 cm 3 mol − 1 for EOE) is expected, but alkoxyethanol molecules being expected to exist in rings of 5/6/7members, it is expected that the molar volume remains positive even though there is possibility of hydrogen bond formation between the C_O group of anisaldehyde and the \OH group of alkoxyethanol, whereas for BOE it is clear from the values from Table 3 that its molar volume is higher

Z. Begum et al. / Journal of Molecular Liquids 178 (2013) 99–112

a

105

b

c

Fig. 1. Plot of excess molar volume deviations against mole fraction of AA(X1) at 303.15 K, (♦) 318.15 K (■), 313.15 K (▲) and 318.15 K (•) for (AA+ MOE), (AA + EOE), and (AA + BOE) systems.

a

b

c

Fig. 2. Plot of adiabatic compressibility deviations against mole fraction of AA (X1) at 303.15 K, (♦) 318.15 K (■), 313.15 K (▲) and 318.15 K (•) for (AA + MOE), (AA + EOE), and (AA + BOE) systems.

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Z. Begum et al. / Journal of Molecular Liquids 178 (2013) 99–112

(132.4630 cm3 mol−1) than the AA (value mentioned above) molecules at 303.15 K indicating a very possible reason for the positive values of VE ‘s. Same is observed in the research analysis of anisaldehyde with cresols by Narendra et al. [15]. In all systems the VE values decreased with a rise in temperature from 303.15 to 318.15 K. This may be attributed to the rise in kinetic energy of interacting molecules and breakage of intermolecular association followed by new hydrogen bond formations. The algebraic values of (VE) for the studied systems are in the order:

a

MOE > EOE > BOE:

3.2. Deviations in adiabatic compressibility Δβad The measure of a change in volume of liquid as a response to a change in pressure, relative to volume at constant temperature is called isothermal or adiabatic compressibility. The deviations in adiabatic compressibility are graphically represented in Fig. 2a, b and c as a function of mole fraction of AA at 303.15 K. The values for βad increase with an increase in temperature and are related to the change of hydrophilic hydration with temperature of oxyethanol with anisaldehyde, and the magnitude of negative values decrease with increasing chain length of the alkoxyethanols. The deviation is positive for BOE, which is an indication of existence of more dispersive forces than association. According to Fort and Moore [26] a negative excess compressibility is an indication of strong hetromolecular interaction in the liquid mixtures which is attributable to charge transfer, dipole–dipole, dipoleinduced dipole interactions, and hydrogen bonding between unlike components, while a positive sign indicates weak interaction and is attributed to dispersion forces (London forces), which are likely to be operative in every cases. The magnitude of the contributions made by these different types of interactions will vary with the components and composition of the mixture. In the present study, the excess compressibility is negative for the binary mixtures of AA + MOE and AA + EOE This observation together with Fort and Moore's result suggests the existence of intermolecular interactions in both above mentioned mixtures, and it is possible that there is a dipole–dipole interaction existing in these mixtures between the carbonyl group (\C_O) of Anisaldehyde and \OH group of oxyethanol, whereas it is positive for AA+ BOE, indicating decreasing ability of the oxyethanol to associate with dissimilar molecule owing to the stearic hindrance effect. The term molecular geometry/cage/skeleton is more appropriate to explain the positive excess molar volumes and negative adiabatic compressibilities, besides hydrogen bonding. Here one must assume that the molecular cages of oxyethanol anisaldehyde binaries as having more spaces still cannot be further compressed, owing to their various orientations. Bond torsions by specified angles, especially in molecules like oxyethanols is a basis for explaining the structural orientations and active centers of reactivity, unlike linear molecules which lie in a single plane and react. These molecules are expected be arranged in a

b Fig. 4. a and b: Molecular models depicting hydrogen bond in the binaries of AA+MOE. Color reference: Blue: carbon atoms, Red: oxygen atoms; white: hydrogen atoms.

haphazard manner without really getting packed tightly, thus bringing positive excess molar volumes and negative compressibilities. Fig. 3a, b, c and d indicates various associated clusters of pure MOE and Fig. 4a and b shows the possible overlap of the electron clouds of AA and MOE, resulting in hydrogen bond formations. Also it is of great interest to expect other possible overlaps of electron clouds (the pi bonded hydrogen of AA and oxygen of MOE) which though may not fully result in hydrogen bond formation but may have effect on over all associations. Reddy et al. [27] also reported that positive values of excess velocity and negative values of excess compressibility are attributable to molecular association and complex formation where as negative values of excess velocity and positive values of excess compressibility are attributable to molecular dissociation. In the present study excess compressibility values are negative for AA + MOE and EOE mixtures which indicate molecular association or complex formation. But for AA + BOE system it is not.

3.3. Excess intermolecular free length (LfE) Excess intermolecular free length (LfE) free length showed an increase with increase of mole fraction of AA in all the systems. The

Fig. 3. a, b, c and d: Molecular models depicting possible associated micilli of MOE (groups of 2, 3, 5 and 7) through intermolecular hydrogen bonding. Color reference: Blue: carbon atoms, Red: oxygen atoms; white: hydrogen atoms.

Z. Begum et al. / Journal of Molecular Liquids 178 (2013) 99–112

a

107

b

c

Fig. 5. plot of deviation in excess intermolecular free length against mole fraction of AA(X1) at 303.15 K,(♦)318.15 K(■),313.15 K(▲) and 318.15 K (•)for (AA + MOE),(AA + EOE), and (AA + BOE) systems.

adiabatic compressibility and free length are the deciding factors of the transmission of ultrasonic velocity in liquid systems. While the pressure is nearly constant, rise in temperature increases the distance between the surfaces of the two molecules. Liquids with longer Lf s have lower ultrasonic velocity values as proposed by Eyring's theory

a

[28]. (AA + BOE) system shows lower ultrasound velocity values, proving lesser associations. Fig. 5a, b and c indicates the LfE deviations against mole fraction of AA at 303.15 K. These results are supported by fact that, in liquids, increases in temperature result in an increase of inter-molecular distance. Therefore the liquid becomes less packed,

b

c

Fig. 6. Plot of deviation in viscosity against mole fraction of AA(X1) at 303.15 K,(♦)318.15(■),313.15 K(▲) and 318.15 K (•)for (AA + MOE),(AA + EOE),and (AA + BOE) systems.

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Z. Begum et al. / Journal of Molecular Liquids 178 (2013) 99–112

Table 4 Coefficients Aj-1 of the Redlich–Kister equation, and the corresponding standard deviations of excess parameters for the binary mixtures of studied anisaldehyde and oxyethanols. (MOE, EOE, BOE). T/K

A0

A1

AA + MOE: βad (10−12 N−1·m2) 303.15 −12.71536 308.15 −10.73392 313.15 −9.79986 318.15 −8.79234

−0.28900 0.40255 0.74388 1.14927

A2

A3

A4

σ

0.92505 1.12241 1.23624 1.37822

0.66185 0.67450 0.68853 0.82982

0.26738 0.24856 0.23986 0.27639

0.00893 0.00071 0.00070 0.00376

VE(cm3·mol−1) 303.15 308.15 313.15 318.15

3.380253 1.761796 0.792072 −0.263128

0.676060 0.718774 0.719809 0.747052

0.142578 0.035177 0.161171 0.160626

0.050867 −0.008175 0.059013 0.060794

−0.025093 0.183862 −0.019521 −0.017459

0.000453 0.001665 0.000462 0.000464

Lf E(10−10 m) 303.15 308.15 313.15 318.15

−0.049183 −0.035084 −0.035068 −0.029761

0.000055 0.004931 0.004831 0.007580

0.019695 0.007299 0.007361 0.016587

−0.000420 0.004554 0.004762 0.006445

−0.009915 −0.001000 −0.001171 −0.017031

0.000401 0.000173 0.000522 0.000119

Δη/m·Pas 303.15 308.15 313.15 318.15

−2.28963 −1.55196 −1.10647 −0.83020

−0.24429 −0.16129 −0.15627 −0.08043

0.07052 0.07962 0.12131 0.20068

−0.05439 −0.05522 0.03374 −0.03238

−0.74204 −0.73995 −0.83931 −0.92743

0.00257 0.00257 0.00370 0.00319

A.A + EOE βad (10−12 N −1·m2) 303.15 −8.07700 308.15 −6.52538 313.15 −6.12854 318.15 −5.47461

−2.70128 −1.87454 −1.38042 −0.81709

−0.72254 −0.43256 −0.29997 −0.02201

−0.17934 −0.09391 −0.07078 −0.00430

0.02548 0.05010 0.15514 0.10613

0.00063 0.00063 0.00193 0.00095

4.73231 3.53438 2.78689 2.03183

1.42144 1.17358 1.02590 0.87574

0.30821 0.27829 0.25932 0.23746

0.05726 0.05907 0.05941 0.09831

0.06867 0.07154 0.07363 0.03089

0.00052 0.00051 0.00467 0.00085

Lf E(10−10·m) 303.15 308.15 313.15 318.15

−0.02154 −0.01541 −0.01092 −0.00613

−0.00644 −0.00325 0.00085 0.00087

−0.00017 0.01609 −0.00181 0.00050

0.00033 −0.00601 −0.00501 0.00005

−0.00305 −0.03786 0.00549 0.00031

0.00006 0.00027 0.00010 0.00010

Δη/m·Pas 303.15 308.15 313.15 318.15

−2.56885 −1.77984 −1.22915 −0.90397

−0.50788 −0.34707 −0.23422 −0.16425

0.00596 0.01384 0.07511 0.08741

−0.05583 −0.05186 −0.03744 −0.04291

−0.66621 −0.62600 −0.71699 −0.70215

0.00243 0.00207 0.00244 0.00263

A.A + BOE βad (10−12 N −1·m2) 303.15 2.07740 308.15 2.62823 313.15 3.85372 318.15 4.51819

3.65470 4.78229 5.94677 6.82979

2.51617 3.35161 4.01658 4.60184

1.44004 1.89497 2.15281 2.41221

0.81578 1.01791 1.06399 1.13088

0.00150 0.00175 0.00171 0.00175

VE(cm3·mol−1) 303.15 308.15 313.15 318.15

5.75989 4.32443 3.59016 2.46530

3.89751 2.94663 2.45533 1.69896

1.78445 1.35081 1.12338 0.77032

0.77448 0.60124 0.50531 0.35025

0.42713 0.36301 0.32306 0.25216

0.00125 0.00125 0.00125 0.00123

Lf E(10−10 m) 303.15 308.15 313.15 318.15

0.02317 0.02950 0.03515 0.03895

0.02421 0.02691 0.02997 0.03305

0.01282 0.01388 0.01571 0.01120

−0.00166 0.00437 0.00703 0.00978

0.00562 0.00388 0.00323 0.01740

0.00022 0.00022 0.00017 0.00018

−3.10900 −2.42300 −1.74926 −1.29008

−1.51959 −1.17610 −0.83698 −0.60436

−0.50590 −0.37666 −0.25083 −0.16625

−0.23439 −0.19110 −0.14572 −0.11255

−0.54127 −0.52012 −0.50116 −0.48949

0.00166 0.00165 0.00163 0.00160

VE(cm3·mol−1) 303.15 308.15 313.15 318.15

Δη/m·Pas 303.15 308.15 313.15 318.15

Z. Begum et al. / Journal of Molecular Liquids 178 (2013) 99–112

109

Table 5 Experimental and calculated values of viscosity (η)for the binary mixtures of Anisaldehyde and studied oxyethanols(MOE+EOE+BOE) at temperatures 303.15 k,308.15 k,313.15 k and 318.15 k. η Expt

ηGN(Eq. (8))

ηKC(Eq. (9).)

ηHB(Eq. (10))

ηH(Eq. (11).)

1.548 1.757 1.986 2.233 2.493 2.757 3.015 3.249 3.438 3.557 3.578

1.548 1.719 1.908 2.115 2.337 2.572 2.812 3.048 3.268 3.452 3.578

1.548 1.712 1.894 2.093 2.308 2.537 2.773 3.009 3.234 3.430 3.578

1.548 1.520 1.523 1.562 1.643 1.774 1.964 2.225 2.570 3.014 3.578

1.218 1.341 1.474 1.617 1.769 1.929 2.092 2.253 2.407 2.543 2.649

1.218 1.316 1.426 1.546 1.678 1.821 1.975 2.139 2.309 2.482 2.649

1.218 1.307 1.406 1.517 1.640 1.776 1.925 2.089 2.265 2.453 2.649

1.218 1.232 1.263 1.315 1.391 1.495 1.632 1.807 2.030 2.307 2.649

1.572 1.805 2.057 2.322 2.594 2.860 3.109 3.324 3.487 3.577 3.578

1.572 1.786 2.016 2.261 2.513 2.765 3.007 3.226 3.406 3.529 3.578

1.572 1.781 2.006 2.246 2.493 2.742 2.982 3.201 3.385 3.516 3.578

1.572 1.536 1.537 1.580 1.669 1.812 2.013 2.282 2.625 3.053 3.578

1.336 1.471 1.613 1.762 1.914 2.066 2.214 2.354 2.477 2.578 2.649

1.336 1.459 1.589 1.726 1.869 2.014 2.160 2.302 2.435 2.553 2.649

1.336 1.451 1.574 1.703 1.840 1.980 2.124 2.267 2.405 2.535 2.649

1.336 1.345 1.374 1.424 1.499 1.600 1.733 1.899 2.104 2.352 2.649

2.403 2.818 3.204 3.540 3.806 3.987 4.077 4.073 3.981 3.811 3.578

2.403 2.786 3.142 3.454 3.703 3.878 3.973 3.984 3.917 3.778 3.578

2.403 2.812 3.193 3.525 3.787 3.967 4.058 4.056 3.969 3.805 3.578

2.403 2.205 2.088 2.048 2.080 2.180 2.344 2.570 2.853 3.190 3.578

η Expt

ηGN(Eq. (8))

ηKC(Eq.(9).)

ηHB(Eq. (10))

ηH(Eq. (11).)

1.490 1.650 1.822 2.005 2.194 2.386 2.573 2.745 2.890 2.993 3.035

1.490 1.618 1.758 1.909 2.071 2.242 2.417 2.593 2.762 2.914 3.035

1.490 1.608 1.738 1.879 2.032 2.195 2.366 2.542 2.718 2.886 3.035

1.490 1.481 1.494 1.532 1.600 1.704 1.850 2.046 2.301 2.626 3.035

1.128 1.229 1.338 1.456 1.580 1.711 1.846 1.982 2.114 2.236 2.340

1.128 1.209 1.298 1.397 1.505 1.624 1.752 1.890 2.036 2.187 2.340

1.128 1.198 1.277 1.366 1.465 1.577 1.701 1.838 1.991 2.158 2.340

1.128 1.147 1.181 1.230 1.298 1.389 1.505 1.653 1.836 2.063 2.340

1.487 1.665 1.854 2.050 2.248 2.443 2.626 2.789 2.919 3.005 3.035

1.487 1.650 1.822 2.003 2.189 2.374 2.553 2.719 2.861 2.970 3.035

1.487 1.642 1.808 1.982 2.161 2.342 2.519 2.685 2.833 2.953 3.035

1.487 1.474 1.487 1.529 1.605 1.719 1.874 2.077 2.334 2.650 3.035

1.250 1.359 1.473 1.592 1.714 1.836 1.957 2.072 2.177 2.269 2.340

1.250 1.349 1.454 1.564 1.679 1.796 1.915 2.032 2.145 2.249 2.340

1.250 1.341 1.437 1.540 1.648 1.761 1.877 1.996 2.114 2.230 2.340

1.250 1.266 1.297 1.345 1.410 1.497 1.607 1.742 1.907 2.105 2.340

2.288 2.613 2.905 3.150 3.334 3.450 3.494 3.468 3.377 3.229 3.035

2.288 2.590 2.862 3.090 3.264 3.377 3.425 3.410 3.335 3.207 3.035

2.288 2.608 2.895 3.136 3.318 3.433 3.478 3.454 3.367 3.224 3.035

2.288 2.115 2.005 1.956 1.963 2.024 2.136 2.295 2.500 2.747 3.035

AA + MOE 303.15 K 1.548 1.502 1.518 1.567 1.656 1.793 1.984 2.242 2.577 3.006 3.578

303.15 K

313.15 K 1.218 1.214 1.258 1.321 1.404 1.513 1.651 1.824 2.037 2.298 2.649

1.490 1.463 1.488 1.537 1.614 1.723 1.870 2.062 2.308 2.617 3.035 318.15 K 1.128 1.129 1.175 1.236 1.312 1.408 1.525 1.669 1.843 2.054 2.340

AA + EOE 303.15 K 1.572 1.521 1.534 1.586 1.682 1.828 2.030 2.294 2.629 3.044 3.578

303.15 K

313.15 K 1.336 1.330 1.371 1.431 1.512 1.617 1.749 1.912 2.108 2.342 2.649

1.487 1.459 1.483 1.535 1.618 1.735 1.891 2.090 2.338 2.641 3.035 318.15 K 1.250 1.251 1.294 1.351 1.423 1.513 1.623 1.755 1.911 2.096 2.340

AA + BOE 303.15 K 2.403 2.197 2.089 2.055 2.090 2.191 2.354 2.575 2.852 3.180 3.578

308.15 K 2.288 2.107 2.006 1.963 1.973 2.035 2.145 2.300 2.499 2.738 3.035

(continued on next page)

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Table 5 (continued) η Expt

ηGN(Eq. (8))

ηKC(Eq. (9).)

ηHB(Eq. (10))

ηH(Eq. (11).)

2.119 2.356 2.563 2.733 2.859 2.937 2.967 2.948 2.886 2.784 2.649

2.119 2.338 2.530 2.689 2.808 2.885 2.917 2.906 2.855 2.768 2.649

2.119 2.351 2.554 2.721 2.845 2.923 2.953 2.937 2.877 2.779 2.649

2.119 1.992 1.911 1.874 1.878 1.921 2.001 2.115 2.263 2.441 2.649

η Expt

ηGN(Eq. (8))

ηKC(Eq.(9).)

ηHB(Eq. (10))

ηH(Eq. (11).)

1.937 2.113 2.266 2.389 2.481 2.538 2.560 2.549 2.506 2.435 2.340

1.937 2.102 2.245 2.362 2.449 2.505 2.529 2.523 2.487 2.425 2.340

1.937 2.109 2.258 2.379 2.469 2.525 2.548 2.539 2.499 2.431 2.340

1.937 1.844 1.785 1.759 1.763 1.795 1.856 1.942 2.052 2.185 2.340

AA + BOE 313.15 K

318.15 K

2.119 1.984 1.912 1.881 1.888 1.932 2.010 2.121 2.262 2.432 2.649

Table 6 Interaction parameters calculated from Eqs. (8) to (11) and the corresponding standard deviations(σ) for the binary mixtures of Anisaldehyde and three oxyethanols under study(MOE,EOE,BOE) at temperatures 303.15 K, 308.15 K 313.15 K, and 318.15 K. T/K

G12

Δ12

Wvis/RT

H12

AA+ MOE 303.15 0.913 308.15 0.696 313.15 0.537 318.15 0.443

0.7402 0.5082 0.3212 0.2359

0.770 0.568 0.420 0.336

0.5985 0.3987 0.2389 0.1692

0.743 0.525 0.370 0.279

0.5712 0.3626 0.2037 0.1329

1.266 1.362 1.260 1.218

0.0131 0.0132 0.0130 0.0132

AA+ EOE 303.15 308.15 313.15 318.15

0.933 0.717 0.524 0.421

0.7773 0.5331 0.3398 0.2457

0.865 0.659 0.473 0.377

0.7063 0.4817 0.3014 0.2159

0.848 0.632 0.440 0.337

0.6887 0.4575 0.2758 0.1891

1.245 1.329 1.339 1.308

0.0112 0.0110 0.0114 0.0111

AA+ BOE 303.15 1.195 308.15 1.053 313.15 0.841 318.15 0.686

1.2995 1.0258 0.7317 0.5340

1.139 1.010 0.804 0.660

1.2230 0.9742 0.6942 0.5105

1.185 1.043 0.831 0.676

1.2856 1.0137 0.7213 0.5250

1.310 1.348 1.431 1.432

0.0076 0.0073 0.0074 0.0073

and hence the density and ultrasonic velocity decreases and the compressibility increases as a result of increased intermolecular distances.

1.937 1.836 1.786 1.766 1.773 1.806 1.865 1.947 2.051 2.176 2.340

3.4. Viscosity deviations The value and magnitude of Δη depend on molecular shape of the components in addition to intermolecular forces. In the present study, the values of deviations in viscosity Δη are all negative in the entire range of composition with a maximum at a mole fraction range of 0.42–0.46 indicating specific interactions at this point between unlike molecules. Deviations in viscosity (ηE) for the mixture of AA with alkoxyethanols at 303.15 K are depicted in Fig. 6a, b, c. The trend in increasing negative deviation of η E is MOE>EOE > BOE. The ηE value shows a systematic increase with increase in temperature for the binary mixtures. Similar results have been reported earlier [29] Also, the deviations in η values are found to be opposite to the sign of excess molar volumes VE for all three binary mixtures, which is in agreement with the views proposed by Brocos et al. [30,31]. A correlation between the sign of η E and VE has been observed for a number of binary solvent systems [32,33], i.e., η E is positive when VE is negative and vice-versa. Same is observed in these binaries under study. The uncertainty in the deviation in viscosity is found to be 0.083%. The binary coefficients and to estimate the standard deviation between experimental and calculated data of these excess values from Eqs. (6) to (7) are represented in Table 4. The experimental and theoretical values of viscosity of the liquid mixtures calculated using Eqs. (8)–(11) are presented in Table 5 and

Fig. 7. Neat FT-IR spectrum of pure anisaldehyde at 303.15 K. (Possible regions of C\C, C\O and C\H stretching are shown with lines.) (note: carbon number is not to be taken into consideration here).

Z. Begum et al. / Journal of Molecular Liquids 178 (2013) 99–112

the interaction parameters derived by all above equations are presented in Table 6 along with standard deviation, σ, values. All the empirical relations gave a reasonable fit, but the viscosity values calculated using Hind et al. are in good agreement with the experimental values. 4. FTIR Study FTIR spectroscopy is a successful method to probe the molecular structure of association effects among molecules since it gives precise information about water sensitive bonds. Generally, these techniques offer the advantages to measure the association properties and hydrogen bonding capability, to assess interactions of alcohol with water by analyzing band shifts and shape. Furthermore, FTIR is also advantageous to evaluate the vibrational properties of bonds through very thin solution films, which are usually difficult to handle for the floating properties of solution [34]. FTIR studies on anisaldehyde have been done by various researchers [24,35,36]. The dipole moment of anisaldehyde is 3.7855D. This is responsible for the formation of dipole induced-dipole interactions with other easily polarisable molecules. The spectra for pure components, and binary mixtures at different concentrations of specific compositions were recorded using Nicolet nexus 670 spectrometer, using KBr pellet in the region (400 to 4000) cm−1 with 4.0 cm−1

111

resolution to investigate the presence of hydrogen bonding and strength of molecular associations. FT-IR spectrum of pure anisaldehyde recorded at 303.15 K is presented in Fig. 7. The hetero-aromatic structure shows the C\H stretching vibrations in the region 3200– 3000 cm−1, which is characteristic region for the ready identification of C\H stretching vibrations. C\H stretching vibrations of heterocyclic compound absorption bands are usually weak, and in many cases it is too weak for detection [24]. Also there are clear bands assigned for C\O vibrations (1323–1290 cm−1) and C\C vibrations (1600– 1400 cm−1). Our study mainly is focused on the changes in intramolecular hydrogen bond intensities and how the addition of anisaldehyde to the oxyethanol is affecting the spectral properties of the strength of hydrogen bonding between unlike molecules. Fig. 8 and Table 7 explain the relative strengths of associations within the binaries at different mole fractions of AA. It is observed that a broad band depicting the hydrogen bond is observed at frequencies between 3640 and 3160 wave lengths in pure alkoxyethanols. There is a linear variation in intensity of the hydrogen bond loop which is existing in the pure components and decreased as the anisaldehyde molecules form associated complexes at specific molar concentrations. In case of MOE, and EOE binaries, the IR graph showed gradual reduction in intensity and wave length. The disappearance occurred at a concentration of 0.75 M of anisaldehyde.

100

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95

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10 3500

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100 95 90

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70 65

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60 55 50 45 40 35

45 4000

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100 90 80

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Fig. 8. Variation in hydrogen bond intensity with mole fraction (X1) for (AA + MOE), (AA + EOE) and (AA + BOE) binary systems at different concentrations as given in Table 7.

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Table 7 Shift in hydrogen bond intensity \OH (υ/cm−1): comparison of all three oxy-alcohols. Pure/binary mixture (AA + oxy-alcohol)

MOE

EOE

BOE

Pure 0.25 M + 0.75 M 0.5 M + 0. 50 M 0.75 M + 0.25 M

3411.47 3421.75 3527.64 3548.75

3407.26 3436.48 3452.56 3466.73

3414.32 3440.38 3467.68 3472.41

A.Anis Fathima et al. [37] studied the changes in spectral features with varying mole fractions of anisaldehyde in a variety of polar and non polar binary mixtures. They found the carbonyl stretching, aldehydic δ (C\H) and ring-breathing modes, showed a linear variation in the peak position for varying concentrations of AA in different solvents. Same is observed in our study. Careful observation of IR intensities revealed that at concentrations of 0.25 M and 0.5 M of the binary mixture, the loop showed little change in frequency where monomeric alkoxyethanols are expected to show the cluster breaking phenomenon by the addition of AA. Here at this point, the dispersive forces are more than the attraction (dipole induced-hydrogen bonding). The formation of intermolecular hydrogen bond is favored more at 0.75 M of anisaldehyde, where the disappearance of intramolecular hydrogen bonding loop has taken place. Shift from lower frequencies to higher frequencies indicate weakening of molecular interactions, it may be inferred that the addition of AA is bringing changes in over all associations within alkoxyethanols, forming a new association through hydrogen bond (C\O…H\O). Since the interactions are weak in case of (AA+ BOE), there is a slight red shift in hydrogen bond intensity, but not total disappearance of the loop. Even the shift is observed only at 0.75 M anisaldehyde, indicating lesser strength of association between BOE, as compared to other alkoxyethanol, which does not permit the formation of intermolecular hydrogen-bonded network even at higher concentrations of AA. The self association of BOE is still being observed at this concentration, indicating all related reasons, like steric hindrance by longer carbon chains, dispersive forces by the monomers, longer intermolecular free lengths, and lesser sound velocities. 5. Conclusion After a thorough study of the behavior of alkoxyethanols with anisaldehyde, at different temperature and concentrations, using ultrasonic, thermodynamic and FTIR techniques, molecular interactions of the type dipole–dipole and dipole induced hydrogen bonding between the components were confirmed, and is found that the interactions between the solvent molecules decrease with increasing chain length of alkoxyethanols. The experimental values of viscosity were correlated with the empirical relations of viscosity and Hind et al. relation gave a good agreement with the experimental values. References [1] H.A. Zarei, H. Iloukhani, Thermochimica Acta 405 (2003) 123–128. [2] H. Iloukhani, H.A. Zarei, Journal of Chemical and Engineering Data 47 (2002) 195–197. [3] B. Lowen, S. Schulz, Thermochimica Acta 262 (1995) 69–82. [4] R. Francesconi, F. Comelli, Journal of Chemical and Engineering Data 44 (1999) 44–47.

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