Partial molar volumes and isentropic compressibilities in mixtures ofc-butyrolactam (n = 5) with 2,2,2-trichloroethanol or2,2,2-triÑuoroethanol or 1,1,1,3,3,3-hexaÑuoropropan-2-ol¤

S. K. Mehta,* A. K. Sharma, Ram Parkash and S. L. ChadhaDepartment of Chemistry, Panjab University, Chandigarh - 160 014, India

The partial molar volumes and isentropic compressibilities of 2,2,2-trichloroethanol, 2,2,2-triÑuoroethanol and 1,1,1,3,3,3-hexaÑuoropropan-2-ol have been obtained in pyrrolidin-2-one at 303.15 K from measurements of excess volume and ultrasonicvelocity. In the mixture of pyrrolidin-2-one and 2,2,2-triÑuoroethanol the V E is negative throughout the composition range, witha tendency to become positive at large x. The other two mixtures present an S-shaped behaviour of V E with composition, beingnegative at low x and positive at high x. Quantitative estimation of di†erent contributions viz. interactional, free volume and P*e†ect to V E have been obtained by utilizing the well known PrigogineÈFloryÈPatterson theory. The ultrasonic velocity data havebeen combined with excess volume to compute molar isentropic compressibility and its excess values is negative in allK

sK

sE. K

sE

the mixtures over the whole composition range and the values vary in the order 2,2,2-trichloroethanol \ 2,2,2-triÑuoroethanol \1,1,1,3,3,3-hexaÑuoropropan-2-ol. Several related quantities have been calculated and presented graphically. The results are com-pared and discussed to gain insight into the changes in molecular association equilibria and structural e†ects in these systems.

Replacement of H by halogen atoms in the alkyl group of analkanol shows a signiÐcant e†ect on dispersion interactions inmixtures. Alkanols are relatively poor proton donors, buthighly electronegative substituents increase their proton-donating ability. Krueger and Mettee1 have found that theintramolecular hydrogen bonding in trihaloethanol increasesin the order a trend which is the reverseF3C\ Cl3C\Br3C,of the normal accepted order of propensity of hydrogen bondsby halogens. The dipole moment2 increases from tribromo-ethanol, 1.73 D, to trichloroethanol, 2.04 D, to triÑuoro-ethanol, 2.52 D. Although trihaloethanols are much strongerproton donors than ethanol, the oxygen atom is correspond-ingly weaker as a base, and spectroscopic evidence suggeststhat trihaloethanols are less associated than ethanol. In com-parison with the large aggregates in ethanol, X-ray di†ractionanalysis of 2,2,2-triÑuoroethanol by OhtakiÏs group3 hasshown that small clusters consisting of two to three tri-Ñuoroethanol molecules are distributed randomly in theliquid, forming an intramolecular (OwHwF), an inter-molecular (OwHwO), or an intercluster (OwHwO) hydro-gen bond.

Although halogenated alkanols are interesting solvents ofindustrial importance, there are only a few reports4h8 ofstudies of excess thermodynamic functions of mixtures involv-ing them. On the other hand, the thermodynamic propertiesof mixtures of aliphatic alkanols have been extensively investi-gated. Recently, results of the measurements of the partialmolar volumes and the molar isentropic compressibilityV12 K1 0of mixtures of c-butyrolactam (n \ 5) i.e. pyrrolidin-2-onewith alkanols over the entire composition range at(C1ÈC10)303.15 K have been reported by Mehta et al.9,10 The inÑuenceof the alkyl chain length of the alkanol and the sensitivity tocomposition on the excess molar properties was investigated.

In addition to high dipole moment, cyclic amides (lactams)possess the basic (CO) and acidic (NH) groups of the verycommon, naturally occurring wCOwNHw peptide bond. Inpyrrolidin-2-one the nitrogen and carbon of a peptide bondare linked by a ring composed of methylene groups. These

¤ Primary data are available as supplementary material (SUP57407 ; 4pp.) deposited with the British Library. Details are availablefrom the editorial office.

compounds11h13 are of special interest because the amidefunctional group is a structural part of peptides, polypeptidesand proteins and they are important for understandingcomplex molecules of biological interest.

As a contribution towards a more comprehensive ther-modynamic description, and to illustrate how the substitutionof alkanol with halogen atoms a†ects the behaviour of thethermodynamic properties of pyrrolidin-2-one and alkanol,we report here the partial molar volume and isentropic com-pressibility measurements of pyrrolidin-2-one and 2,2,2-tri-chloroethanol or 2,2,2-triÑuoroethanol or 1,1,1,3,3,3-hexa-Ñuoropropan-2-ol at 303.15 K. Several related quantities havebeen calculated and presented graphically to enhance visualimpact and to gain insight into the various interactions oper-ating in the mixtures.

ExperimentalThe materials used were pyrrolidin-2-one (PY), 2,2,2-trichloro-ethanol (TCE), 2,2,2-triÑuoroethanol (TFE) and 1,1,1,3,3,3-hexaÑuoropropan-2-ol (HFP) all from Fluka. Pyrrolidin-2-onewas dried with CaO and fractionally distilled, as describedelsewhere.14 TCE, TFE and HFP were used as received. Priorto use, all the chemicals were stored for several days in theabsence of light over A4 molecular sieves. The purity of thehalogenated alkanols was checked by comparing their den-sities (measured using an Anton Paar digital precisiondensimeter) with literature15 values at 293.15 K. The densityvalues at 303.15 K of PY, TCE, TFE and HFP are listed inTable 1.

The measurement of excess volumes was carried out in acontinuous dilution dilatometer. The dilatometer wasimmersed in a water bath controlled to better than ^0.01 K.Temperature control was achieved using a circulating waterbath, regulated to ^0.01 K, using a proportional temperaturecontroller. The temperature was calibrated to 303.15^ 0.01 Kwith a precision platinum resistance thermometer. Details ofthe experimental set-up and the measuring procedure havebeen described elsewhere.17 The results for V E are estimatedto be accurate to ^0.002 cm3 mol~1.

An ultrasonic time intervalometer (UTI-101) from Innova-tive instruments, based on the pulse-echo-overlap technique

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Table 1 Densities o, ultrasonic velocities u, isobaric thermal expan-sivities and molar heat capacities for the component liquids ata

pC

p303.15 K

o u ap

Cpcomponent /kg m~3 /m s~1 /10~4 K~1 /J K~1 mol~1

PY 1103.0 1617.64 6.346 166.10aTCE 1544.6 1171.04 8.021 113.96bTFE 1373.3 832.14 11.220 177.78cHFP 1589.8 679.36 17.141 140.32b

a Ref. 14. b Estimated by group additivity, ref. 16. c Ref. 7.

(PET) coupled with an oscilloscope, was used for the ultra-sonic velocity, u, measurements. The frequency of sound was2.0 MHz. The cell for the speed of sound measurements wascalibrated with water18 as a reference. The uncertainty in themeasurement of u was within ^2 ] 10~2 m s~1.

Fig. 1 Excess volumes V E for x pyrrolidin-2-oneÈ(1[ x) haloge-nated alkanol : TCE; TFE; (]) HFP; (ÈÈÈ) ETOH;(…) (L)(É É É É É É É) Pr-2-OH

Fig. 2 Partial molar excess volumes and for x pyrrolidin-2-V1 1E V1 2EoneÈ(1[ x) halogenated alkanol : TCE; (ÈÈÈ) TFE; (]) HFP(…)

Results and Discussion

Excess volume

The excess volumes V E of the binary mixtures of PY withTCE or TFE or HFP have been determined experimentally at303.15 K. The results are presented in Fig. 1 in the form of V Evs. x, the mole fraction of PY. In the mixture of PY and TFEthe V E is negative throughout the composition range, with atendency to become positive at large x. The other two mix-tures present an S-shaped behaviour of V E with composition,being negative at low x and positive at high x. For compari-son, the V E curves of mixtures10,19 of PY with ethanol andpropan-2-ol are included in Fig. 1. The results have been Ðttedto a RedlichÈKister equation of the form

V E(cm3 mol~1) \ x(1 [ x) ;i

Ai(2x [ 1)i (1)

The values for the coefficient and the standard deviation ofAiÐt for each system are given in Table 2.

Numerous IR investigations20h25 have shown that self-association of PY is relatively strong. The halogenated alka-nols are also associated but to a lesser degree than normalalkanols. The mixing of PY with each halogenated alkanol isexpected to make signiÐcant changes in the hydrogen-bondingequilibria and electrostatic interactions, with di†erent contri-butions to V E.

The important e†ects which are expected to contribute tothe value of V E may be arbitrarily divided into physical,chemical and structural contributions. Physical contributionscomprise non-speciÐc physical interactions between in†

ŒCxOPY and a hydrogen atom in the substituted alkanol, that con-tribute positively to V E. The breaking up of the liquid order ofboth associated PY and halogenated alkanol also makes apositive contribution to V E (chemical e†ect). Structural e†ectswhich contribute negatively, arise from geometrical Ðtting ofPY and halogenated alkanol into each other and are due todi†erences in molar and free volumes of these components.The molar volumes of TCE, TFE and HFP are 96.72,72.85 and 105.70 cm3 mol~1, respectively, compared with77.16 cm3 mol~1 for PY. The free volumes of these halo-genated alkanols and PY are 0.145, 0.556, 0.655 and 0.099cm3 mol~1, respectively. One may conclude that, in the presentset of mixtures, all three e†ects contribute to V E, but the struc-tural ones are larger at lower x, whereas physical and chemi-cal e†ects dominate at high concentration of PY.

Fig. 1 also shows a comparison of V E for PYÈTCE or TFEand PYÈHFP with that of ethanol and propan-2-ol with PY.The V E values of PYÈhalogenated alkanols are considerablyless negative than those of PYÈalkanols at similar tem-peratures. Since halogenated compounds are much strongerproton donors than alkanols, a strong interaction of the typeCxO¼HwO might be expected. The stronger interactionmight lead to a greater breakdown of the hydrogen-bondedstructure of halogenated compounds and PY, and may par-tially account for the less negative V E in these mixtures.

A more adventurous strategy to gain insight into the behav-iour of various mixtures involves the generation of plots of

Table 2 Least-square coefficients of eqn. (1) and standard deviation, p, of x pyrrolidin-2-oneÈ(1[x) halogenated alkanol binary mixtures at303.15 K

PY] A0 A1 A2 A3 A4 A5 A6 A7 p XE (x\0.5)

TCE V E [0.3618 0.9226 [0.4081 0.3808 [0.2502 [2.2734 [0.7403 3.0889 0.002 [0.0904K

sE [8.86 5.20 [1.92 1.40 [1.21 [2.91 0.08 3.36 0.003 [2.22

TFE V E [0.1747 1.3072 0.0619 1.6589 0.5137 [2.6631 0.0727 1.6601 0.003 [0.0437K

sE [25.46 5.38 2.23 0.89 [3.59 1.13 3.51 [2.44 0.006 [6.36

HFP V E 0.2167 3.2204 [3.3486 [1.5898 1.8227 3.2527 [1.3799 [2.8610 0.004 0.0542K

sE [137.97 64.02 [28.56 [5.59 4.75 2.49 5.55 [7.51 0.005 [34.48

2566 J. Chem. Soc., Faraday T rans., 1998, V ol. 94

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Table 3 Molar volumes for pure halogenated alkanol, limiting partial molar volumes excess partial molar volumes of halogenatedV2 V1 20 , V1 2E, 0alkanol at inÐnite dilution, molar isentropic compressibility partial molar isentropic compressibilities of halogenated alkanol at inÐniteKs, 2 ,

dilution and the parameter at 303.15 KK1 20 Sk

V2 V1 2E, 0 V1 20 Ks, 2 K1 20/cm mol /cm3 mol~1 /cm3 mol~1 /10~8 Pa~1 cm3 mol~1 /10~8 Pa~1 cm3 mol~1 S

k

TCE 96.72 [0.37 96.36 4.566 4.235^ 0.07 [0.606^ 0.11TFE 72.85 2.35 72.20 7.661 7.348^ 0.09 [2.099^ 0.16HFP 105.78 0.07 105.77 14.406 13.055^ 0.42 [6.518^ 0.78

partial excess molar volumes of the respective components, V1 1Eand These have been calculated from:V1 2E .

V1 1E \ V1 [ V11 \ V E/x ] x(1[ x)[L(V E/x)/Lx]p, T (2)

V1 2E \ V2 [ V12 \ V E/(1 [ x)] x(1[ x)

] [LMV E/(1 [ x)N/L(1[ x)]p, T (3)

where and represent the partial molar volumes of theV11 V12components 1 and 2.Fig. 2 depicts the excess partial molar volumes of PYV1

iE

and halogenated alkanols. The limiting values, andV1 20 V1 2E, 0for PY and halogenated alkanols are listed in Table 3 togetherwith the values of molar volumes of respective components.

The negative partial excess molar volumes may be indica-tive of a strong interaction by H bonding, accompanied byonly minor (entropy-increasing) destruction of halogenatedalkanol structure, or the Ðtting of PY into halogenatedalkanol cavities by interstitial accommodation, or both. Thepossibility of Ðtting should be closely related to the relativesize of the components. The negative and oppositeV1 1E, 0 V1 2E, 0clearly indicate that, in the dilute PY region, structural e†ectsare dominating, whereas destruction of associated structures isimportant in the dilute halogenated alkanol region.

Quantitative estimation of di†erent contributions to V E canbe obtained by using the well known PrigogineÈFloryÈPatterson26 theory. This theory has been described in detailby Patterson and co-workers27,28 and has been widely used toanalyse excess thermodynamic properties for di†erent kinds ofmixtures, including polar components, by several authors.Their approximate expression for V E in terms of three contri-butions is

V Ex1V 1* ] x2V 2*

\(v8 1@3 [ 1)v8 2@3t1h2(4/3v8 ~1@3 [ 1)P1*

X12 (interactional)

[(v8 1 [ v8 2)2(14/9v8 ~1@3 [ 1)t1t2

(4/3v8 ~1@3 [ 1)v8(v8 curvature)

](v8 1 [ v8 2)(P1* ] P2*)t1t2

P2* t1 ] P1*t2(P* e†ect)

(4)

where and are the characteristic pressure and volumePi* V

i*

of the pure components. represents the site fraction, theh2 v8reduced volume and t the contact energy fraction given by

t1\ 1 [ t2 \/1P1*

(/1P1* ] /2 P2*)(5)

The various parameters of the pure components and themixture obtained with Flory theory29,30 are listed in Table 4.

The values of the interaction parameter for each binaryX12mixture have been calculated using experimental equimolarV E values and are listed in Table 5 together with equimolarvalues for each of the three contributions to V E.

Table 4 Isothermal compressibility reduced volume character-kT

, v8 ,istic volume V *, characteristic temperature T * and characteristicpressure P* of components at 303.15 K

V */cm3component kT/TPa~1 v8 mol~1 T */K P*/J cm~3

PY 403.19 1.1702 65.94 6951 653.36TCE 640.19 1.2082 80.03 5986 557.07TFE 1208.08 1.2759 57.10 4959 458.34HFP 2033.89 1.3824 76.46 4096 488.24

An analysis of each of the three contributions to V E showsthat the and the corresponding interactional contributionX12term are always positive. There is nearly a 10-fold increase inthese values in TFE and 20-fold in HFP over those in theTCE system (Fig. 3). Both free volume and P* contributionsare negative with TCE\ TFE\ HFP.

Overall, it may be concluded from the theoretical results inTable 5 and Fig. 3, that both the interactional term and P*are important in magnitude in these mixtures. Whereas the P*contribution is larger than the interactional term in the chlo-rinated system, the latter contribution dominates the Ñuori-nated systems. The overall magnitude is decided by the thirdcontribution i.e. the free volume term. In comparison to thetwo contributions above, its e†ect is less in TCE and highlysigniÐcant in HFP.

Table 5 Calculated values of the three contributions to the excessvolume from the PFP theory for x pyrrolidin-2-oneÈ(1[ x) haloge-nated alkanol at 303.15 K

calculated contributions

freeX12/J cm~3 interaction volume P* e†ect

TCE 8.15 0.0618 [0.0408 [0.1113TFE 87.99 0.7602 [0.2436 [0.5602HFP 181.75 2.3510 [1.1926 [1.1042

Fig. 3 Values of the three contributions to the excess volume fromthe PFP theory for x pyrrolidin-2-oneÈ(1[ x) halogenated alkanol ;

interactional ; (ÈÈÈ) free volume; (É É É É É É É) P* e†ect(…)

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Fig. 4 Excess isentropic compressibilities for x pyrrolidin-2-oneÈKsE

(1[ x) halogenated alkanol ; TCE; TFE; (]) HFP; (ÈÈÈ)(…) (L)ETOH; (É É É É É É É) PR-2-OH

By considering the three di†erent contributions included inPFP theory, it is possible to understand the sign and magni-tude of V E. Although the interactional term is large and posi-tive in these systems, the sign and magnitude of the internalenergy term, together with the magnitude of the free volumecontribution, are very important in producing the S-shapedbehaviour. The theory will be able to reproduce the S-shapedcurves when the P* contribution is negative and large and thefree volume contribution is relatively large. The positiveregion of V E corresponds to a high concentration of the com-ponent with lower P* parameter, i.e. halogenated alkanol,whereas the negative region corresponds to a high concentra-tion of the component with higher P* parameter, i.e. PY.

Ultrasonic velocity

The measurement of ultrasonic velocity, in combination withdensity, enables the accurate determination9 of molar isentro-pic compressibility coefficient and its apparent value, whichcan be used to provide information about the nature of theinteraction operating in the mixtures.

The values of u have been combined with V E to calculatethe isentropic compressibilities using the relation

ks\

[; xiVi] V E]

(u2 ; xiM

i)

\V

Mu2(6)

where M is the molar mass of the mixture.

Pa~1 cm3 mol~1 for x pyrrolidin-2-oneÈFig. 5 Ks, 1E [ K

s, 2E /10~8(1[ x) halogenated alkanol : TCE; TFE; (]) HFP(…) (L)

Further, the corresponding molar quantity is given by

Ks\ V k

s\

V 2Mu2

(7)

which assumes that dissipative e†ects are negligible and thatthe hydrodynamic equation of motion can be linearised. TheV E data were extrapolated to the mole fractions of the ultra-sonic velocity experiments using from eqn. (1).A

iExcess molar isentropic compressibilities were obtainedKsE

by subtracting from the isentropic compressibility forKs

Ksid

the corresponding ideal mixture

KsE\ K

s[ K

sid (8)

It can be shown31,32 that

Ksid\ ; x

i

CK

s, i]T (V

iap, i)2

Cp, i

D

[GT (; x

iVi)2(; x

iap, i)2

(; xiC

p, i)H

(9)

Eqn. (2) was again utilised for Ðtting data. The coeffi-KsE

cient and standard errors are also listed in Table 2. Fig. 4shows as a function of x at 303.15 K for the systemsK

sE

studied. Negative deviations in are observed for all theKsE

mixtures, in the sequence HFP[ TFE[ TCE.The trends in V E are di†erent than those of since theK

sE

size of the molecule a†ects V E and di†erently.KsE

The apparent molar compressibility of a solute in a solu-/ktion is deÐned33,34 by the following equation

/k, 2 \ k

s/

v, 2]x0M0(ks [ k

s, 0)x2o0

(10)

where

/v, 2\ M0

A x0x2 o0

B(o0 [ o) ]

M2o

(11)

and and are the density, mole fraction and isentro-o0 , x0 ks, 0pic compressibility coefficient of the solvent, respectively ; M is

the relative molar mass of the solvent mixture ; and arex2 M2the mole fraction and relative mass of the solute component ;and o and are the density and isentropic compressibilityk

scoefficients of the solution mixture.The limiting value of the apparent molar isentropic com-/

kpressibilities were calculated by a linear extrapolation usingthe least-squares Ðt to the equation :

/k\ /

k0 ] S

kx2 (12)

where is the inÐnite dilution molar isentropic compress-/k0

ibility. is the experimental slope, indicative of soluteÈsoluteSkinteractions arising from dilute concentration e†ects. At an

inÐnite dilution, i.e. inÐnite dilution partial molar/k0 \ K1 0

isentropic compressibilities. The values of and are givenK1 0 Skin Table 3.

A comparison of limiting values of chloro/Ñuoro com-K1 20pounds with the corresponding molar isentropic compress-ibility where can be considered as theK

s, 2 \ (ks, 2 V

m, 2) Ks, 2partial compressibility of the solute when dissolved in itself,

i.e. pure liquid, shows a close agreement for TCE and TFEbut deviations are observed for HFP. The near agreement inthe and values of solute in solution and pure liquidK1 20 K

s, 2for TCE and TFE implies that, after dissolution, the molecu-lar volume of the solute molecules is practically una†ectedand that the molecules are in a force Ðeld similar to thatpresent in the pure liquid state. The small disagreement forHFP can be analysed in terms of structural and geometricalcompressibilities as suggested by Hall and Sile and co-workers.35,36 The structural compressibility results from the

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Fig. 6 Experimental and calculated ultrasonic velocities u (L), uJ(È ÉÈ É) and (ÈÈÈ) for x pyrrolidin-2-oneÈ(1[ x) halogenateduNalkanol : I, TCE; II, TFE; III, HFP. The error (%) being 0.43, 3.5, 7.9for and 0.78, 2.0, 1.5 for in TCE, TFE and HFP, respectively.uJ uN

breakdown of intermolecular bonds, whereas geometricalcompressibility is due to simultaneous compression of themolecules, leading to a decrease in the average intermoleculardistance.

The parameter when positive, indicates the presence ofSk,

relatively strong interactions between respective components.In the present set of mixtures, shows negative values, thusS

k, 2the possibility of strong interactions in these mixtures is ruledout.

The deviations from ideal behaviour may be estimated bycalculating the excess apparent isentropic compressibilities ofPY and halogenated compounds as

Ks, 1E \ /

k, 1[ /k, 10 (13)

Ks, 2E \ /

k, 2[ /k, 20 (14)

where and represent the apparent isentropic com-/k, 1 /

k, 2pressibilities at a particular mole fraction and and/k, 10 /

k, 20are the apparent molar isentropic compressibilities at inÐnitedilution for PY and halogenated compounds. The di†erencebetween and should give an estimate of the devi-K

s, 1E Ks, 2Eations from ideal behaviour. A linear plot with negative slopeof this di†erence with composition will indicate ideal solutionbehaviour.

Fig. 5 shows the variation of with mole frac-(Ks, 1E [ K

s, 2E )tion of PY for all the binary mixtures. It is clearly evident thatthe mixture PYÈTCE tends to approach ideality whereasPYÈTFE, and PYÈHFP show strong departures from ideality.The non-ideality in these mixtures varies as HFP[TFE[ TCE.

For comparison, the theoretical values of ultrasonic veloci-ties, u, are computed using JunjieÏs and Nomoto equations :

JunjieÏs equation :37

uJ\ [(x1M1/o1)] (x2M2/o2)]/M(x1M1 ] x2M2)1@2

] [(x1M1/o12u12)] (x2 M2/o22 u22)]1@2N

Nomoto equation :38

uN \ [(x1R1 ] x2 R2)/(x1V1] x2V2)]3

where R is RaoÏs constant given by Ri\ V

iui1@3.

Fig. 6 shows the computed and values in comparisonuJ uNwith the experimental values for all the mixtures. The resultsclearly demonstrate that the two simple expressions predictthe experimental data extremely well. This is in line with ourearlier observation9 for PYÈalkanol mixtures.

References

1 P. J. Krueger and H. D. Mettee, Can. J. Chem., 1964, 12, 340.2 H. D. Purohit, H. S. Sharma and A. D. Vyas, Bull. Chem. Soc.

Jpn., 1975, 48, 327.3 T. Radani, S. Ishiguro and H. Ohtaki, J. Solution Chem., 1989, 18,

771.4 A. Cooney and K. W. Morcom, J. Chem. T hermodyn., 1988, 20,

735 ; 1469.5 L. Pikkarainen, J. Chem. T hermodyn., 1988, 20, 481 ; 1989, 21,

1177.6 M. Denda, H. Touhara and K. Nakanishi, J. Chem. T hermodyn.,

1987, 19, 539.7 M. Nakamura, K. Chubachi, K. Tamura and S. Murakami,

J. Chem. T hermodyn., 1993, 25, 525.8 S. Miyanaga, K. Chubachi, M. Nakamura, K. Tamura and S.

Murakami, J. Chem. T hermodyn., 1993, 25, 331.9 S. K. Mehta, R. K. Chauhan and R. K. Dewan, J. Chem. Soc.,

Faraday T rans., 1996, 92, 1167.10 S. K. Mehta, R. K. Chauhan and R. K. Dewan, J. Chem. Soc.,

Faraday T rans., 1996, 92, 4463.11 B. Garcia, R. Alcalde and J. M. Leal, J. Phys. Chem. B, 1997, 101,

7991.12 B. Garcia, R. Alcalde, J. M. Leal and J. S. Matos, J. Chem. Soc.,

Faraday T rans., 1997, 93, 1115 ; 1996, 92, 3347.13 F. J. Hoyuelos, B. Garcia, R. Alcalde, S. Ibeas and J. M. Leal, J.

Chem. Soc., Faraday T rans., 1996, 92, 219.14 J. A. Riddick and W. B. Bunger, Organic Solvents : Physical

Properties and Methods of PuriÐcation, Wiley-Interscience, NewYork, 3rd edn., 1970.

15 Beilstiens Handbuch der Organischen Chemie. 1, iv16 D. N. Rihani and L. K. Doraiswamy, Ind. Eng. Chem. Fundam.,

1965, 4, 19.17 E. Dickinson, D. C. Hunt and I. Mclure, J. Chem. T hermodyn.,

1975, 7, 731.18 V. A. Del Grosso and C. W. Mader, J. Acoust. Soc. Am., 1972, 52,

1442.19 P. Pitra-Honkmenen, J. Chem. Eng. Data, 1987, 32, 303.20 J. A. Walmsley, E. J. Jacob and H. E. Thompson, J. Phys. Chem.,

1976, 80, 2745.21 J. A. Walmsley, J. Phys. Chem., 1978, 82, 2031.22 J. Jadzyn, J. Malecki and C. Jadzyn, J. Phys. Chem., 1978, 82,

2128.23 A. V. Hambly and R. H. Laby, Aust. J. Chem., 1964, 14, 318.24 G. Malewski and R. Koing, Spectrochim Acta, 1964, 20, 565.25 R. Koing and G. Malewski, Spectrochim. Acta, 1968, 24, 219.26 I. Prigogine and R. Defay, Chemical T hermodynamics, Longman,

London, 5th edn., 1969, p. 8.27 P. Tancrede, P. Bothorel, P. St. Romain and D. Patterson,

J. Chem. Soc., Faraday T rans. 2, 1977, 73, 15.28 P. St. Romain, H. T. Van and D. Patterson, J. Chem. Soc.,

Faraday T rans. 1, 1979, 75, 1770.29 P. J. Flory, J. Am. Chem. Soc., 1965, 87, 1883.30 P. J. Flory and A. Abe, J. Am. Chem. Soc., 1964, 86, 3563.31 G. C. Benson and O. Kiyohara, J. Chem. T hermodyn., 1979, 11,

1061.32 G. Douhe� ret, M. I. Davis, L. J. Fjellanger and H. Hoiland,

J. Chem. Soc., Faraday T rans., 1997, 93, 1943.33 J. E. Desnoyers, Pure Appl. Chem., 1982, 54, 1469.34 N. P. Rao and R. E. Verrall, J. Coll. Interface Sci., 1998, 121, 85.35 L. Hall, Phys. Rev., 1948, 73, 775.36 W. Slie, A. Donfor and T. Litovitz, J. Chem. Phys., 1946, 44, 1106.37 Z. Junjie, J. China Univ. Sci. T echn., 1984, 14, 298.38 O. Nomoto, J. Phys. Soc. Jpn., 1958, 13, 298.

Paper 8/03236J ; Received 29th April, 1998

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