Indian Journal of Chemistry Vol. 44A, March 2005, pp. 51 I -51 5

Molecular interactions in binary mixtures of anisole with benzyl chloride,

chlorobenzene and nitrobenzene at 303.15 K: An ultrasonic, volumetric,

viscometric and refractive index study

A Ali *, A K Na in , D Chand & B Lal

Department of Chemistry, Jamia Millia lslamia (Central Uni versity), Jnmia Nagnr, New Delhi 110 025 , Indi n

Emai l: anwnr.ch@j mi.ernet.in

Received 24 May 2004; revised 6 December 2004

Densiti es, ultrason ic speeds, viscositi es, and refractive indi ces of binary mixtures of anisole with benzyl ch loride, chl orobenzene and nitrobenzene, including those of the pure liquids, have been measured at 303.15 K over the entire composition range. Using these ex periment al data, the deviati ons in isentropic compressibil­ity, ultrasonic speed, viscosity and refractive index, excess molar volume, excess free energy of activation of viscous now, excess rheoc hore, partial molar compressibility and volume of benzy l chloride, ch lorobenzene and nitrobenzene in ani so le at infinite dilution, have been calculnted. The variat ions of these properties with compositi on suggest that the strength of interactions in these mi xtures foll ow the order: benzy l ch loride> nitrobenzene> chlo­robenzene.

!PC Code: Int. Cl.7 GO IN ; BOIJ 19/10

The deri ved excess properties from the ex pen­mental measurements of density, ultrasonic speed, viscosi ty and refractive index provide valuable infor­mation that allow us to have better understanding of the structure of liquids and intermolecular interactions in liquid mixturest·3

. Our research group is actively engaged in the study of thermodynamic, volumetric, acoustic and transport properties of non-aqueous bi­nary/ternary liquid mixtures4

·5

. The present work deals with the study of binary mixtures of anisole with benzyl chloride (BC), chlorobenzene (CB) and nitro­benzene (NB) at 303. 15 K over the whole composi­tion range . These benzene derivatives are versatile compounds, as they find application as solvents in many chemical and technological processes. Anisole is a well-known electron-pair donor, whereas BC, CB and NB are reported as electron-acceptors.

In recent years, several workers have studied the physico-chemical behaviour of binary mixtures of anisole with methanollbenzene6

, pentyl alcohol iso­mers7, dimethyl sulphoxide8

, 1, I ,2,2-tetrachloro-

ethane9 and l-chloronaphthalene 10 by using various experimental techniques. To the best of our knowl­edge, there has been no study on anisole+ BC/CB/NB binary mixtures from the point of view of thei r ultra­sonic and refractive index behaviour. Joshi et a/. 11 and Yiswanthan et a/. 12 have reported the densities and viscosities of anisole+ CB/NB binary mixtures.

We report herei n the experimental values of densi­ti es (p), ultrasonic speeds (u) , viscosities (YJ) and re­fractive indices (n) of pure liquids (anisole, benzyl chloride, chlorobenzene, nitrobenzene) and of their binary mixtures, with anisole as common component , at 303.15 K over the entire composition range. From the experimental values of p, u, Y( and n, the values of

.,E *E E b..ks, v , b..u , b..Y(, G -, [W] , and b..n have been calcu-lated. In addition, the values of apparent molar com­press ibility an~ volume, _K~.2 . and Vq,,2, res pectively and those of K0~_2 , and V0~ .2 of BC, CB and NB in anisole at infinite dilution have been calculated. The variations of these properties with composition have been used to interpret the nature and extent of inter­molecular interactions in these binary mixtures.

Experimental Anisole, benzyl chloride, chlorobenzene and nitro­

benzene (all S. D. Fine Chemicals, India ; purity > 99%) were used without further purification . But prior to use, all the chemicals were stored over 0.4 nm molecules sieves to reduce water content, if any, and were degassed. All the mixtures were prepared by mass in a dry box and were kept in special airti ght bottles. The weighings were done on electronic bal­ance (Afcoset ER-120A) with a precision of ± 1.0 x 10-4 g. The probable error in mole fraction was esti­mated to be less than ± 0.000 I.

The densities of pure liquids and their binary mixtures were measured using a single-capillary pycnometer made of Borosil glass having a bulb ca­pacity of 8 x 10-6 m3 as described elsewhere45

. The accuracy in density measurements was found to be ±O.lkgm-3

.

The ultrasonic speed in pure liquids and their bi­nary mixtures was measured using single-crystal vari­able-path interferometer operating at 3 MHz with an accuracy of± 0.05 %.

512 INDIA N J CHEM, SEC A, MARCH 2005

The viscosities of pure liquids and their binary mixtures were measured by using Ubbelohde type suspended-level viscometer. The viscometer was cali­brated with pure water. The viscometer contai ning the test liquid was allowed to stand for about 30 mi n. in a thermostatic water bath so that the thermal fluctua­tions in viscometer were minimized. ~he accuracy in viscosity data was within± 3 x 10-6 N s m-2

.

fractive index were obtained for sodium D light. The calibration of the refractometer was clone by measur­ing refractive indices of pure water and benzene at the experimental temperature. The reproducibi lity of re­fractive index measurement was within± 0.0002.

The temperature of the test liquids during the meas­urements was maintained at an accuracy of± 0.02 Kin an electronically controlled thermostatic water bath .

The refractive indices were measured by using a thermostated Abbe refractometer. The values of re-

The reliability of the experimental measurements

of p, u, T] and n was checked by comparing the ob-

Table !-Densities (p), ultrasoni c speeds (11), viscosit ies (YJ ) and refractive indices (11 ) of bi nary mi xtures as a function of mole fraction x 1 of anisole at 303. 15 K

x , p(kgm-3) u (m s- 1

) 11 (10-3 N s m-2) II

Anisole + Benzyl chloride

0.0000 1094.8 1356.6 1.11 2 1 1.5326

0.1045 1085.0 1363.2 1.2446 1.53 13

0. 191 1 1077 .4 1369.3 1.3623 1.530 1

0.3040 1066.2 1375.5 1.4384 1.5283

0.4094 1055.7 1379.8 1.4658 1.5264

0.5 182 1044. 1 1382.9 1.4495 1.5242

0.6 162 1033.0 1384.8 1.3944 1.5220

0.7 196 1020.8 1386.9 1.2996 1.5 196

0.8053 1009.9 1387.8 1.1920 1.5174

0.9137 996.3 1389.7 1.06 13 1.5 147

1.0000 984.4 1390.6 0.9310 1.5 125

Anisole + Chloroben zene

0.0000 1095 .6 1251.7 0.7 148 1.5182

0.0864 1085.2 1262.6 0.7392 1.5 173

0.1933 1072.6 1276.5 0.7667 1.5 165

0.2875 1061.7 1288.9 0.7900 1.5 158

0 .3805 1051. 1 130 1.4 0.8112 1.5151

0.4904 1038.8 13 16.6 0.8348 1.5145

0 .5826 1028.7 1329.5 0.8538 1.5 140

0.6914 1016.9 1345.0 0 .8755 1. 5 136

0.7790 1007 .6 1357.7 0 .8922 1.5 132

0.8905 995 .8 1374.1 0.9 132 1.5129 1.0000 984.4 1390.6 0.9310 1.5 125

Anisole + Nitrobenzene

0.0000 11 93.3 1442.6 1.6752 1.5484

0.0972 1172.4 1438.3 1.5547 1.5452

0.1829 11 54.0 1434.5 1.4375 1.5424

0.2642 11 36.7 1430.7 1.3410 1.5397

0.3916 11 09 .7 1424.3 1.2242 1.5352

0.4829 1090.6 1419.6 l.l470 1.5320

0.5830 1069.8 1414.3 1.0800 1.5284

0 .6854 1048.7 1408.8 1.0222 1.5246

0.7963 1025.9 1402.7 0.98 10 1.5205 0.8977 1005.2 1396.8 0 .9600 1.5 166 1.0000 984.4 1390.6 0.9310 1.5 125

NOTES 513

served values of these properties of pure liquids with the corresponding literature values. The observed val­

ues of p for anisole, CB and NB , at 303. 15 K, are

984.3, 1095.6 and 1193.3 kg m-3, respectively (lit.

values : 984.3 1\ 1095.5 11 and 1193 .2' 1 kg m-3

, respec­tive ly); the observed values of u for anisole, CB and

NB , at 303.15 K are 1390.6, 1251.7 and 1442 m s- 1,

respectively (lit. va lues: 1393.08, 1249 14 and 1443.3 15

m s- 1, respectively); the measured values of 11 for an­

isole, CB and NB, at 303.15 K, are 0.9310,0.7148 and 1.6752 cP, respective ly (lit. values: 0.93156

,

0.7155 11 and 1.6662 11 cP, respectively); and the ob­served va lues of n for anisole, at 303 .15 K, is 1.5 125 (lit . value: 1.511 8\

Results and discussion The ex perimental va lues of p, u, 11 and 11 o f pure

ani so le, BC, CB, NB and twenty-seven binary mix­tures of aniso le with BC, CB and NB, over the entire compos it ion range expressed by mo le f ract ion, x 1 of anisole at 303. 15 K are li sted in Tab le l . From these

experimental values of p, u, 11 and 11 , the dev iatio ns in isentropic compressibility (11k,), deviations in ultra­sonic speed (/1 11 ), excess mo lar volume (V\ devia­

tions in viscosity (1111 ), excess free energy of activa­ti on of viscous flow (G*E), excess rheochore ((RE])

and deviatio ns in refractive index (/111) have been cal­cul ated by using the following re lations:

M , = k, - (<jl 1k, 1 + <!>2kd (1)

!111 = 11 - (-r, tt , + x2u2) (2)

V0 = x 1M 1(l/p - llp, )+xzMz(l/p-l/p2) (3)

1111 = 11 - (x,11, + x2112) (4)

c *E = RT [ln(11 V)- x 1ln(T] 1 V1) - x2 ln (112 V2)] (5)

[RE] = [R]- {x 1[R,] + x2[R2]} (6)

!111 = 11 - ( <P 111 1 + <!>2n2) (7)

where <!> is the vol ume fracti on and M is the mo lar mass. Subscripts 1 and 2 stand for the pure compo­nents, ani so le and BC/CB/N B, respecti vely . k5 , V and [R] are the isentropic co mpress ibility, mo lar vo lume and rheochore, respective ly and were evaluated by the following re lati o ns:

k, = l /u2p

V = (x 1M 1 + x2M2)/p

[R] = VT] 118

. .. (8)

... (9)

.. . ( l 0)

The values or 11k,.11u, v', /1Tj , c *E [RE] and/111 of the binary mi xtures were fitted to a Redlich-Ki ster type polynomial eq uation:

5

yE = x 1xz LA; (1- 2x1 )i-1 . . . (11) i =l

d o · , £ *E E where r IS 11k, or 11u or v or 1111 or G or [R ] and

11n. The coefficient, Ai of the fitting Eq . (11 ), evalu­ated using least-squares method and the standard de­

viations cr (rE) were calculated as:

( E "' E , ,E 2/ 1/2 <J Y ) = [.L.(Y expl- l cu i) (h- k)] . . . (12)

where h is the number of experimental data points and k is the number of Ai coeffic ient considered (Table 2). yEcal was calculated fro m Eq. (1 1) using the best-fit values of A;.

The observed values of excess properti es depend upon several factors, which are of physical and/or chemical nature 16

• The physical contributions involve di spersion forces and no n-specif ic (weak) interac­

tions, which contribute to negative 11u , /1Tj , G*E and

11n or positi ve 11ks and 0 values. Chemical contri bu ­tions in vo lve breaking up of the associates present (if

any) , wh ich result in positive 11ks and 0 or negative

11u , 1111 , c *E and 11n values. It also involves specific interactions such as formation of H-bo nds, charge­transfer complexes or strong dipo le interactions be­

tween component molecul es that lead ro positi ve !111 ,

1111 , c *E and /111 o r negative 11k, and 0 values.

Results show that 11k, and 0 val ues are positive for

ani sole + CB mixtures, whereas 11k, and 0 are nega­tive for an isole + BC/NB mi xtures over the whole composition range. This suggests the presence of weak interactions (dispersion forces) between anisole and CB mo lecules, i.e., aniso le-CB interaction is weaker than anisole-aniso le or CB-CB interacti ons. The presence of specific interacti on may be attributed to the formatio n of charge-transfer complexes be­tween unlike mo lecules with aniso le acting as e lectron pair donor and BC/NB as e lectron pair acceptors. The

magnitudes of negative dev iations in 11k, and 0 from rectilinear dependence on composition for the mix­tures under study follow the sequence: BC > N B > CB, which clearly suggests that the strength of inter­action between aniso le and CB/NB/BC mo lecules wou ld foll ow the order: BC > NB > CB. Thi s, in turn , is the order of e lectron accepti ng ability of the func­

tional groups present in these molecul es, i.e, -CH2CI

> -N02 > -Cl. As expected, the values of 11u are negative for ani sole + CB mixtures and positi ve for aniso le + BC/NB mixtures over the entire composi­

tion range. In general, the negative deviations in 11u

514 IND IAN J CHEM, SEC A, MARCH 2005

Table 2-Coefficients A; of Eq. (I I) and standard dev iations a (yE) for the binary mi xtures

Property A, A 2 A J A4 As (J ( yE)

Anisole + Benzyl chloride

M, ( 1 o-'' m2 w') -4.1538 -1.1209 -0.1469 1.9969 1.1658 0.0124

yE (I o-6 m3 mol- 1) -2.179 1 0.2280 0.3943 0.8598 -0.2250 0.0130

1111 (m s-1) 35.0733 18.7362 1.1 477 -23.0646 - 16.476 0. 1107

1117 (10-3 N s m-2) 1.7347 0.3462 -0. 18 12 -0.3888 -0. 1910 0.002 1

C'E (kJ mol- 1) 3.5604 0.3658 0.2575 -0.678 1 -0.3819 0.0042

[REJ [10-6 m3 mor 1 (N s m-2)

118] 18.2275 3.0545 1.5303 -3.1752 -2.5062 0.0140

11n 0.7631 0.1330 -0.0420 -0.008 1 -0.0985 0.0018

Anisole + Chlorobenzene

M , ( 10- 11 m2 W 1) 0.7239 0. 1617 0.0769 -0.028 1 0.0225 0.0012

0 (10-6 m3 mol- 1) 0.1567 0.0917 -0.0353 -0.0011 0.0278 0.0016

1111 (m s-1) -1 2.9247 -0.6283 -1.3933 0.2527 0.441 0.0171

11 17 (10-3 N s m-2) 0.0557 0.0174 -0.0277 -0.02 0.062 0.0006

c'E (kJ mol- 1) 0.2662 0.0751 0.0448 -0.0283 -0.02!8 0.0002

[RE] [10-6 m3 mol-1 (N s m-2)118

] 1.1 894 0.3981 0. 1849 -0. 161 3 0.1306 0.0012

11n -0.3584 -0.0207 0.2898 -0. 1788 -0.3942 0.0028

Anisole + Nitrobenzene

M , ( 10- 11 m2 N- 1) -3.1676 -0.0483

0 ( 10-6 m3 mol- 1) -0.5704 0.1679

1111 (m s- 1) 8.3637 1.1949

111] ( 10-3 N s m-2) -0.6668 -0.0548

C'E (kJ mol- 1) -0.9619 0.2653

[REI [10-6 m3 mol- 1 (N s m-2) 118] -5.5185 1.52 12

11n 0.4916 0.1403

indicate weak interactions, whereas posit ive dev ia­

tions in !J.u indicate specific interactions between un­like molecu les leading to the formation of complex 17

at the composition where !J.u exhibits max ima. The

observed trends in !J.u are in accordance with the above view, suggesting that the inte ract ions in these systems follow the order: BC > NB > CB. Thi s fur­

ther reinforces the conclusion drawn from !J.ks and 0 values.

The values of M ] and c *E are positive for aniso le+ BC mixture and negative for anisole + NB mixture; while M ] and c *E values for aniso le + CB mixture show small positive deviations over the entire compo­

sit ion range. The positive l111 and c *E val ues indicate the presence of significant interaction between the

co!::::-'onent molecules2, while negative values of l111

and c *E indicate that dispersion forces are dominant in

the mixture2· '

6. The presence o f extrema in l111 vs x 1

and c *E VS x, plots for anisole+ CB and an isole+ NB mixtures suggests the fo rmation of molecular com­plexes in solution 18

. The absence of well -defined

-0.3083 0. 1448 0.3803 0.0019

-0.2463 -0. 1404 0.1665 0.0020

4.2217 -2 .7778 -4.7388 0.019 1

-0. 1836 -0.044 0.6209 0.0018

-0.33 -0.1304 1.2427 0.0037

-1.9975 -0.7866 6.8208 0.0215

0.0386 -0.2073 -0.0368 0.0029

maxima for l111/G*E vs x 1 plots indicates that there is no complex formation 18 for the system anisole+ CB .

Excess rheochore [RE] values are large positive for aniso le + BC, negative for aniso le + NB and then be­come small positive for anisole + CB binary mixtures over the whole composition range. The positive [RE] values indicate specific interac tion, while the negative va lues indicate the presence of weak interaction be­tween un like molecu les in the mixtures . The trends in the variation of [RE] with x 1 are in good agreement

With the behaviour Of !J.ll and c *E for the SystemS studied. Similar conc lusion regarding the behaviour of [RE] va lues were also arrived at by Corrodini et a/. 19

for N,N-dimethylformamide + I ,2-ethanedio l binary mixtures.

The dev iations in refractive index , !J.n are negative for anisole + CB mi xtures and positive for both an­isole + NB/BC bin ary mixtures over the whole vo l­ume fraction range. Recentl y, Brocos et a /.20 sug­

ges ted that the deviati ons in !J.n from ideal behaviour defined on vo lume fractio n basi s cou ld be corre lated with the excess molar volumes of the binary mixtures.

NOTES 515

Table 3-The values of K0

9_2, K*1, 2, t:J.K, 11"~_2 , v*1u and i':J. V of 13C, Cl3 and N13 in anisole for the binary mixtures

Component 2 K o 2 K* b2

(!0- 14 m5 N- 1 mo l- 1) (10- 14 m5 N- 1 mo l-1)

Benzyl chloride 5.2599 5.7389 Chlorobenzene 6.0498 5.9852 Nitrobenzene 3.7738 3.7398

These workers correlated the 1111. values with VE val­ues for a number of binary mixtures and observed that 11n values follow a trend opposite to that followed by 0 values. The observed trends in 1111. vs Xt and oppo­site trends in 0 vs Xt plots for the present binary mixtures truly support the above view.

The apparent molar compressibility (K¢>.2) and ap­parent molar vo lume CV¢>. 2) of BC, CB and NB in an­isole were calcu lated by using the relations2 t·22

:

K¢.2 = K*q,.2 + KsE lx2 ... (13) * E/ V.p.2 =V 2+Vx2 .. . (14)

where K,E = [k, VO] is the excess molar compressibility of the mixture; x2, K* d!.2 and v* 2 are the mole fraction , molar isentropic compressibility and molar volume of component 2 (BC/CB/N~), respectively; The partial molar ~ompressibility , K 0

¢>.2 and partial molar vol­ume, VOq,.2 of BC, CB and NB in anisole at infinite dilution were obtained by the method described else­where2t'23 . The deviations in Kd!.2. and Vq,2. at infinite dilution , 11K and 11 V, respectively , were evaluated by

. h I . ? t ustng t e re at10ns- :

11K= j(o <t>.2- K' <1>.2 ( 15)

(16)

The values of j(o ¢.2, K* .;..2, 11K, VO .;.,2, v* 2 and 11 V are listed in Table 3. Perusal of Table 3 indicates that the deviations 11K are negative for anisole + BC/NB mixtures and positive of for anisole + CB mixture, i.e., the molar compressibilities of BC and NB mole­cules in the mixture at infinite dilution ( K 0 q..2) are less than their molar compressibility (K*,p ) in the pure state while K0 q,.2 of CB is greater than its K*<l>. 2 in the pure state. Also, the deviation 11 V (Table 3) are nega­tive for anisole + BC/NB and positive for anisole + CB mixture, indicating that on mixing there is a con­traction in vo lume for anisole+ BC/NB mixtures and an ex pansion in volume for anisole + CB mixture. The magnitude of 11K and 11 V values clearly suggest that the strength of interactions in these mixtures should foll ow the order: BC > NB > CB . This further reinforces our earli er view regarding interactions in

!:J.K 11"2 v * 2 i':J.V

0 0- 15) (I 0--4 m3 mo l- 1) ( lQ-4 1113 mor I) c 1 o-6)

-4.790 1.1350 1.1563 -2 .13

0.646 1.0282 1.0274 0 .08

-3.806 1.0259 1.03 17 -0.58

these mixtures predicted by using the functions 11k,. 11u, VO, 1111, c *E, (RE] and 11n .

Acknowledgement AKN is thankful to DST, New Delhi for financial

support under the SERC Fast Track Young Scientist Scheme.

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