J. Chem. Thermodynamics 1996, 28, 1083–1092

Speeds of sound in and isentropic compressibilities

of (1,1,2,2,-tetrachloroethane+anisole,

1,4-dioxane, methylethylketone, and pyridine)

at T=303.15 K

Jagan Nath

Chemistry Department, Gorakhpur University, Gorakhpur 273009, India

Measurements of speeds of sound u have been made in binary mixtures of1,1,2,2-tetrachlorethane (CHCl2CHCl2) with anisole (C6H5OCH3), 1,4-dioxane (C4H8O2),methylethylketone (CH3COC2H5), and pyridine (C5H5N) at T=303.15 K. Values of uhave been used to calculate the apparent excess speeds of sound Du and the isentropiccompressibilities kS for these mixtures. The excess isentropic compressibilities kE

S have alsobeen calculated from the values of kS. The kE

S have been found to be highly negative for{xCHCl2CHCl2 + (1− x)CH3COC2H5}, and very slightly negative for {xCHCl2CHCl2 +(1− x)C4H8O2}. The kE

S is very slightly negative at low x, and very slightly positive at higherx for {xCHCl2CHCl2 + (1− x)C6H5OCH3}. The kE

S is also very slightly negative for{xCHCl2CHCl2 + (1− x)C5H5N} at low x and, compared with {xCHCl2CHCl2 +(1− x)C6H5OCH3}, the kE

S is more positive for {xCHCl2CHCl2 + (1− x)C5H5N} at higher x.Values of kE

S for the various systems have been discussed in the light of interactions betweenthe components. 7 1996 Academic Press Limited

1. Introduction

Binary liquid mixtures of 1,1,2,2-tetrachloroethane (CHCl2CHCl2) with anisole(C6H5OCH3), 1,4-dioxane (C4H8O2), methylethylketone (CH3COC2H5), and pyridine(C5H5N) are of considerable interest from the viewpoint of the existence of electrondonor–acceptor interaction resulting in the formation of intermolecular complexesbetween the components. The specific interaction of C5H5N with CHCl2CHCl2 isdue to the presence of lone-pair electrons on the nitrogen atom of C5H5N which actsas an n-donor for CHCl2CHCl2. The presence of lone-pair electrons on the oxygenatoms of CH3COC2H5 and C4H8O2 can make these compounds act as n-donorsand, as described by Mulliken,(1) C6H5OCH3, which contains an –OCH3 group andan aromatic ring system, can act as an np-type donor towards CHCl2CHCl2, whichcan be involved in the formation of hydrogen bonds with, and act as a s-acceptortowards C5H5N, C6H5OCH3, CH3COC2H5, and C4H8O2. It is known that C4H8O2

forms, 1:1 and 1:2 complexes(2–4) with CHCl3, CH2Cl2, CH2ClCH2Cl, and CHClCCl2in the liquid state, and it forms(5,6) 1:2 complexes with CCl4, CHCl3, and CH2Cl2in the solid state. From relative permittivity studies,(7,8) it is known that C5H5Nforms intermolecular complexes with CHCl3 and CHClCCl2 in the liquid state, and

0021–9614/96/101083+10 $18.00/0 7 1996 Academic Press Limited

J. Nath1084

solid–liquid phase equilibrium studies have revealed(5,9) the formation of a 1:2complex of C5H5N with CCl4, and a 1:1 complex with CHCl3. Further, thesolid–liquid phase equilibrium studies show that C6H5OCH3 forms a 1:1 complex(10–12)

with TiCl4, and a 1:1 complex(13) with CCl4, and the values of the excess relativepermittivities(14) indicate that there exist specific interactions between the componentsof the systems of C6H5OCH3 with CCl2CCl2, and CCl4. Extensive studies concerningthe interactions of the electron-donor components C5H5N, C6H5OCH3, CH3COC2H5,and C4H8O2 with a more complicated chloroalkane CHCl2CHCl2 have not been done.The values of the excess isentropic compressibilities (as obtained from the speeds ofsound u in binary liquid mixtures) are known(15) to shed light on the existence ofspecific interactions between the components. Hence, in the present work,measurements of speeds of sound u have been made in binary liquid mixtures ofCHCl2CHCl2 with C6H5OCH3, C4H8O2, CH3COC2H5, and C5H5N, and the resultsobtained are interpreted.

2. Experimental

Liquid 1,1,2,2-tetrachloroethane (SRL) and methylethylketone (SRL) of AR qualitywere shaken with potassium carbonate solution, separated, and then dried overanhydrous potassium carbonate, followed by fractional distillation. Anisole (SRL)of AR quality was distilled from sodium, and 1,4-dioxane (SRL) of u.v. spectralgrade quality, stored over sodium wire, was used. Pyridine (SDS) of h.p.l.c. qualitywas used without further purification. The densities r* of the pure liquid componentswere determined using a single-capillary pyknometer (capacity about 25 cm3) madeof Pyrex glass. The capillary had a 1-mm bore and an etched mark near the top, andcould be closed with an outside cap. All masses were measured with an uncertaintyof 21·10−5 g using a K.Roy (model no. K-15 super) balance. The uncertainty in r*is estimated to be of the order of 22·10−5 g·cm−3. The values of r* are given intable 1. The refractive indices n*D of the pure liquids were determined atT=(298.152 0.01) K, with an accuracy of 20.0002, using a thermostatted Abberefractometer (Carl Zeiss, Germany). The values n*D of the pure liquids are also givenin table 1. The speeds of sound u in pure liquids and their binary mixtures were

TABLE 1. Densities r*, refractive indices n*D , cubic expansion coefficients a*, isobaric molar heat capacities C*p , speeds of sound u*,isentropic compressibilities k*S , isothermal compressibilities k*T , and molar volumes V*m of pure component liquids at T=303.15 K

Component r*/(g·cm−3) n*D 103a*/K−1 u*/(m·s−1) k*S/TPa−1 k*T/TPa−1

Obs. Lit. Obs. Lit.

C*pJ·K−1·mol−1

V*mcm3·mol−1

C5H5N 0.97286 0.97281 a 1.5076 b 1.50745 c 1.036 d 130.07 f 1398.6 525.5 728.9 81.309C6H5OCH3 0.98464 0.98462 a 1.5145 b 1.51430 c 0.960 e 208.57 f 1387.3 527.7 674.8 109.628CH3COC2H5 0.79449 0.79452 a 1.3762 b 1.3764 c 1.310 d 145.46 c 1171.5 917.1 1241.7 90.760C4H8O2 1.02232 1.02230 a 1.4202 b 1.42025 c 1.106 d 149.61 f 1324.2 557.8 771.4 86.183CHCl2CHCl2 1.57857 1.57860 a 1.4912 b 1.4910 c 1.011 d 166.77 c 1138.8 488.5 686.1 106.330

a Reference 16. b The values of n*D are at T=298.15 K. c Reference 17. d Derived from densities in reference 16 and 17. e Reference 18.f See text; C*p for C6H5OCH3 is 208.57 J·K−1·mol−1 at T=304.75 K.

u and kS of binary mixtures 1085

measured at a frequency of 3 MHz, using a quartz-crystal ultrasonic interferometer(supplied by Mittal Enterprises, New Delhi, India). The mixtures of the various liquidcomponents were prepared by mass in a cell with a volume of about 15 cm3. Thequartz crystal was fixed at the bottom of the measuring cell, and could be excitedat its resonant frequency to produce sound waves of frequency of 3 MHz in theexperimental liquid in the cell by using a high frequency generator. A micrometer(Mitutoyo Manufacturing Company Ltd., Japan) with an accuracy of 20.0001 cm,was provided at the top of the cell. The metallic reflector plate (held parallel to thequartz crystal) could be lowered or raised through a known distance in theexperimental liquid, and thus the wavelength of the sound waves was determined bynoting the distance covered by the reflector plate between its positions at the timesof occurrence of the successive maxima of the anode current as shown by themicroammeter fixed on the high frequency generator. The operation of theinterferometer was tested by measuring u in pure samples of C6H6, C6H5CH3, CCl4,CHCl3, CH3COCH3, n-C6H14, and n-C7H16 at temperatures of 298.15 and 303.15 K,which were controlled with an accuracy of 20.01 K, the results of which have beenpublished elsewhere.(18) The imprecision in u is of the order of 20.5 m·s−1.

3. Results and discussion

The speeds of sound u* in pure liquids C5H5N, C6H5OCH3, CH3COC2H5, C4H8O2,and CHCl2CHCl2 at T=303.15 K are given in table 1, and the values of u in mixturesof CHCl2CHCl2 with C6H5OCH3, C4H8O2, CH3COC2H5, and C5H5N at T=303.15 Kare given in table 2. The present values of u* in C6H5OCH3, CH3COC2H5, C5H5N,and CHCl2CHCl2 at T=303.15 K are (1387.3, 1171.5, 1398.6, and 1138.8) m·s−1,which are in good agreement with the earlier(8,18–20) values {1387.3, 1171, 1399, and1137 (interpolated value)} m·s−1 respectively for the above liquids at T=303.15 K.The experimental values u for the various mixtures have been used to calculate theapparent excess speeds of sound Du from the relation:

Du= u−Sxiu*i , (1)

where u*i refers to the speed of sound in the pure component i and xi is the molefraction of the component i in the mixture. The results have been fitted by the methodof least-squares with the equation:

Du/(m·s−1)= x(1− x)· sn

i=1

Ai(2x−1)i−1, (2)

where x is the mole fraction of CHCl2CHCl2 in the mixture. The values of thecoefficients Ai of equation (2), and the standard deviations d(Du)/(m·s−1) for thevarious mixtures are given in table 3. The values of the isentropic compressibilitieskS for the mixtures of CHCl2CHCl2 with C6H5OCH3, C4H8O2, CH3COC2H5, andC5H5N, were obtained from the relation:

kS = (VEm +V id

m )/(u2·SxiMi ), (3)

J. Nath1086

TABLE 2. Speeds of sound u, densities r, isentropic compressibilities kS, and the excess isentropiccompressibilities kE

S at T=303.15 K

x u/(m·s−1) r/(g·cm−3) kS/TPa−1 kES/TPa−1

{xCHCl2CHCl2 + (1− x)C6H5OCH3}0.0296 1377.6 1.00178 526.0 −0.820.0871 1357.8 1.03515 524.0 −1.100.1222 1345.5 1.05556 523.3 −0.720.1786 1327.8 1.08843 521.1 −1.140.2088 1318.2 1.10607 520.3 −0.960.2481 1306.2 1.12907 519.1 −0.870.2767 1297.2 1.14584 518.6 −0.410.3253 1283.4 1.17440 517.0 −0.340.3665 1271.5 1.19868 516.0 +0.110.4107 1259.5 1.22478 514.7 +0.410.4290 1254.6 1.23561 514.2 +0.580.4941 1238.2 1.27423 511.9 +0.730.5140 1233.0 1.28606 511.5 +1.100.5589 1222.2 1.31280 509.9 +1.260.6020 1212.0 1.33853 508.6 +1.700.6350 1204.8 1.35827 507.2 +1.660.6799 1195.2 1.38517 505.4 +1.760.7135 1188.0 1.40535 504.2 +2.010.7521 1180.3 1.42856 502.5 +2.010.7978 1171.2 1.45609 500.7 +2.280.8360 1164.0 1.47914 499.0 +2.360.8718 1158.0 1.50078 496.9 +1.960.9188 1150.2 1.52925 494.3 +1.650.9559 1144.8 1.55176 491.7 +0.90

{xCHCl2CHCl2 + (1− x)C4H8O2}0.0214 1317.0 1.03707 555.9 −0.070.0676 1303.2 1.06842 551.1 −1.000.1078 1291.2 1.09518 547.7 −1.110.1419 1281.5 1.11750 544.9 −1.150.1686 1274.6 1.13475 542.4 −1.530.1931 1268.0 1.15040 540.6 −1.400.2355 1257.5 1.17708 537.3 −1.420.2721 1249.2 1.19972 534.1 −1.840.3079 1240.8 1.22151 531.7 −1.550.3424 1234.0 1.24218 528.7 −2.010.3672 1228.2 1.25685 527.4 −1.500.4157 1219.3 1.28507 523.4 −2.020.4496 1212.6 1.30444 521.4 −1.640.4964 1205.0 1.33069 517.5 −2.290.5422 1197.5 1.35584 514.3 −2.380.5859 1190.5 1.37934 511.5 −2.270.6302 1184.0 1.40268 508.6 −2.270.6630 1179.4 1.41964 506.4 −2.350.7106 1173.0 1.44379 503.4 −2.330.7534 1167.0 1.46501 501.2 −1.870.7987 1162.0 1.48699 498.1 −2.190.8411 1156.8 1.50710 495.8 −1.940.9071 1149.0 1.53753 492.6 −1.25

u and kS of binary mixtures 1087

TABLE 2—continued

x u/(m·s−1) r/(g·cm−3) kS/TPa−1 kES/TPa−1

{xCHCl2CHCl2 + (1− x)CH3COC2H5}0.0282 1167.0 0.82097 894.4 −9.050.0701 1160.8 0.85983 863.1 −20.300.0971 1156.8 0.88455 844.8 −25.760.1354 1152.2 0.91922 819.5 −33.040.1789 1148.0 0.95803 792.0 −40.280.2087 1144.8 0.98427 775.2 −43.290.2449 1141.9 1.01578 755.0 −46.960.3202 1136.4 1.08000 717.0 −50.980.3980 1132.8 1.14449 680.9 −52.660.4517 1131.3 1.18787 657.8 −52.420.5610 1129.2 1.27326 615.9 −47.730.6305 1129.0 1.32549 591.9 −42.720.6786 1130.0 1.36069 575.6 −39.280.7102 1130.2 1.38340 565.9 −36.100.7683 1131.6 1.42432 548.3 −30.320.8086 1132.2 1.45210 537.2 −25.400.8462 1133.4 1.47759 526.8 −20.980.9013 1135.8 1.51431 511.9 −14.410.9516 1137.0 1.54726 499.9 −7.05

{xCHCl2CHCl2 + (1− x)C5H5N}0.0535 1375.0 1.01474 521.2 −1.760.1140 1348.2 1.06047 518.8 −1.380.1968 1315.2 1.12044 516.0 −0.540.2473 1297.8 1.15560 513.8 −0.600.3156 1273.8 1.20157 512.9 +1.300.3609 1259.5 1.23108 512.1 +2.300.4266 1239.0 1.27258 511.9 +4.620.4543 1231.8 1.28963 511.0 +4.760.4748 1225.3 1.30207 511.5 +6.020.5656 1203.0 1.35556 509.7 +7.480.6200 1191.0 1.38635 508.5 +8.160.7039 1175.5 1.43211 505.3 +7.760.7941 1161.0 1.47908 501.6 +6.940.8712 1150.8 1.51752 497.6 +5.300.9279 1145.0 1.54486 493.7 +3.09

using the excess molar volumes VEm for the various mixtures at T=303.15 K,

determined recently,(21) with an accuracy of 20.002 cm3·mol−1 with a two-limbeddilatometer. In equation (3), xi is the mole fraction of the component i in the mixture,V id

m =SxiV*i is the molar volume corresponding to the ideal mixture, and Mi isthe molar mass of the component i. The values of V*i of the pure components givenin table 1 were used to estimate V id

m for use in equation (3) for calculating kS.The values of the isentropic compressibilities k*S of the pure component liquidsC5H5N, C6H5OCH3, CH3COC2H5, C4H8O2, and CHCl2CHCl2, obtained fromequation (3), by using r* from table 1, are reported in the table, whereas the kS valuesof the mixtures are given in table 2. The imprecision in kS is of the order of20.5 TPa−1. Also given in table 2 are the values of the quantity (SxiMi )/(VE

m +V idm ),

J. Nath1088

TABLE 3. Values of the coefficients Ai of equation (2), and the standard deviations d(Du) for the variousmixtures at T=303.15 K

Mixture A1 A2 A3 A4 d(Du)/(m·s−1)

{xCHCl2CHCl2 + (1− x)C6H5OCH3} −106.994 3.934 1.609 −24.478 0.30{xCHCl2CHCl2 + (1− x)CH3COC2H5} −100.989 32.174 −0.425 1.151 0.25{xCHCl2CHCl2 + (1− x)C4H8O2} −108.591 34.328 −3.853 0.26{xCHCl2CHCl2 + (1− x)C5H5N} −198.168 6.070 7.174 0.48

which refers to the calculated densities r of the mixtures. The imprecision in r

is estimated to be of the order of 22·10−5 g·cm−3. Also given in table 1 isthe isothermal compressibility kT of the pure liquids, which was calculated from thecubic expansion coefficient a, and the isobaric molar heat capacity Cp,m, usingthe equation:

kT = kS + a2VT/Cp,m. (4)

The values of a and Cp,m used to calculate k*T of pure liquids from the above equationare given in table 1 with references. The value of Cp,m for C6H5OCH3, as reportedin reference 17, is 208.57 J·K−1·mol−1 at T=304.75 K, which was used for thepresent analysis of kS at T=303.15 K. Normally, DCp,m/DT is small for organicliquids, and thus its use may not affect the present conclusions. The values of Cp,m

for C5H5N, and C4H8O2 given in table 1, were estimated from the correspondingstates method,(22) using the ideal gas heat capacity reported by Stull et al.,(23) and thevalues of acentric factor v and the critical temperature Tc from reference 22.

The values of the excess isentropic compressibilities kES given in table 2 were

estimated from the isentropic compressibilities kS of the mixtures using theequation:

kES = kS − kid

S , (5)

where kidS was obtained from the relation:(24,25)

kidS = (f1k*T,1 +f2k*T,2)− {T(x1V*1 + x2V*2 )(f1a*1 +f2a*2 )2/(x1C*p,1 + x2C*p,2)}

=f1[k*S,1 + {TV*1 (a*1 )2/C*p,1}]+f2[k*S,2 + {TV*2 (a*2 )2/C*p,2}]−

{T(x1V*1 + x2V*2 )(f1a*1 +f2a*2 )2/(x1C*p,1 + x2C*p,2)}, (6)

where

fi = xiV*i /(x1V*1 + x2V*2 )= xiV*i /V idm , (7)

and V*i , k*S,i , k*T,i , a*i , and C*p,i are the molar volume, isentropic compressibility,isothermal compressibility, cubic expansion coefficient, and isobaric molar heatcapacity of the pure component i.

u and kS of binary mixtures 1089

TABLE 4. Values of the coefficients Bi of equation (8), and the standard deviations d(kES ) for the various

mixtures at T=303.15 K

Mixture B1 B2 B3 B4 d(kES )/TPa−1

{xCHCl2CHCl2 + (1− x)C6H5OCH3} 4.423 9.892 −3.432 18.140 0.23{xCHCl2CHCl2 + (1− x)CH3COC2H5} −201.486 74.320 −41.974 20.735 0.33{xCHCl2CHCl2 + (1− x)C4H8O2} −8.757 −3.249 −5.439 0.22{xCHCl2CHCl2 + (1− x)C5H5N} 25.064 42.283 −20.091 0.39

The kES for the various mixtures, obtained through equation (5), has been fitted by

the method of least-squares to the equation:

kES /TPa−1 = x(1− x)· s

n

i=1

Bi(2x−1)i−1. (8)

The values of the coefficients Bi of equation (8), along with the standarddeviations d(kE

S ) are given in table 4. The kES has been plotted against x(CHCl2CHCl2)

in figure 1.The values of kE

S may be visualized in terms of strength of interactions operatingbetween the components of any given system. The negative values of kE

S for a givensystem are due to a closer approach of unlike molecules, leading to a reduction involume and compressibility. The different types of forces that can exist between thecomponents of given systems are the dispersion forces, and the charge–transfer,hydrogen bonding, dipole–dipole, and the dipole–induced dipole interactions. Thedispersion forces lead to attraction between the molecules, and relative magnitudesof 1–1, 2–2, and 1–2 type interactions in a mixture of components 1 and 2 areimportant in determining the excess properties. If the components of a mixture donot differ greatly in shape and size, the dispersion forces should produce a positivecontribution to kE

S . However, the charge–transfer, hydrogen bonding, dipole–dipole,and dipole–induced dipole interactions should create negative contributions to kE

S .Dispersion forces operate in all systems, and for a system in which there is more thanone type of interaction between the components, the kE

S values would be the netresult of the contributions from all types of interaction. Table 2 and figure 1 showthat throughout the entire range of x, kE

S is highly negative for{xCHCl2CHCl2 + (1− x)CH3COC2H5}, and slightly negative for {xCHCl2CHCl2 +(1− x)C4H8O2}. For {xCHCl2CHCl2 + (1− x)C6H5OCH3}, the kE

S is veryslightly negative at low x, and very slightly positive at higher x, with inversion ofsign occurring at x1 0.35. The kE

S is also very slightly negative for{xCHCl2CHCl2 + (1− x)C5H5N} at low x, and as compared with kE

S for{xCHCl2CHCl2 + (1− x)C6H5OCH3}, the values of kE

S are more positive for{xCHCl2CHCl2 + (1− x)C5H5N} at higher x, with inversion of sign occurring atx 1 0.25. At x = 0.5, kE

S for the various systems have the sequence:C5H5NqC6H5OCH3 qC4H8O2 qCH3COC2H5.

J. Nath1090

FIGURE 1. Plot of kES against x for the various systems at T = 303.15 K: W,

{xCHCl2CHCl2 + (1− x)C6H5OCH3}; r, {xCHCl2CHCl2 + (1− x)C4H8O2}; Q, {xCHCl2CHCl2 +(1− x)CH3COC2H5}; q, {xCHCl2CHCl2 + (1− x)C5H5N}.

Further, the values of VEm are found(21) to be negative throughout the entire

composition range for {xCHCl2CHCl2 + (1− x)CH3COC2H5}, {xCHCl2CHCl2 +(1− x)C4H8O2}, {xCHCl2CHCl2 + (1− x)C6H5OCH3}, and {xCHCl2CHCl2 +(1− x)C5H5N} at T=303.15 K, with values of VE

m at x=0.5 equal to (−0.690,−0.226, −0.079, and −0.077) cm3·mol−1, respectively, for the various systemsabove. The data(21) show that the values of the changes of relative permittivitieson mixing Do as calculated from the relative permittivities o of the mixtures atT=303.15 K, using the relation Do= o−Sxio*i (where o*i refers to the relativepermittivity of the pure component i ) are highly positive for {xCHCl2CHCl2 +(1− x)C5H5N}, and {xCHCl2CHCl2 + (1− x)CH3COC2H5}, and slightly negativefor {xCHCl2CHCl2 + (1− x)C6H5OCH3}, and {xCHCl2CHCl2 + (1− x)C4H8O2}.The relative permittivities exhibit positive deviations(7) from the molefraction mixture law for (trichloromethane+pyridine) in which case a strongintermolecular complex is formed(9) between the components. The present highlynegative values of kE

S , along with highly negative values of VEm, and high positive

u and kS of binary mixtures 1091

values(21) of Do for {xCHCl2CHCl2 + (1− x)CH3COC2H5} indicate that there existstrong specific interactions leading to the formation of a molecular complex betweenthe components in the liquid state. Further, negative values of kE

S , along with negativevalues(21) of VE

m, for {xCHCl2CHCl2 + (1− x)(C4H8O2)} indicate the existence of aspecific interaction between the components. The high positive values(21) of Do,and the negative values(21) of VE

m for {xCHCl2CHCl2 + (1− x)C5H5N}, also indicatethe existence of specific interaction between the components in the liquid state.The very slightly negative values of kE

S at low x, and positive values of kEs at high

x , for {xCHCl2CHCl2 + (1− x)C5H5N}, can be seen as being due to thepredominance of the contributions to kE

S from non-specific interactions over thosedue to specific interactions, and that the C5H5N molecules are self-associated(26)

through hydrogen bonding. The negative values(21) of VEm for {xCHCl2CHCl2 +

(1− x)C6H5OCH3}, may be taken to indicate the likelihood of the presence ofspecific interaction between CHCl2CHCl2 and C6H5OCH3, the very slightly negativevalues of kE

S at low x , and very slightly positive values of kES at higher x for this

system, do not support this viewpoint.

The author gratefully acknowledges the financial support received from the Councilof Scientific and Industrial Research, New Delhi, India.

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(Received 25 January 1996; in final form 21 March 1996)

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