Indian Journal of Pure & Applied Physics Vol. 41. November 2003, pp. 849-854

Ultrasonic study of Inolecular interactions in binary liquid Inixtures: acrolien & cinnan1aldehyde in methanol, cyclohexane & p-dioxane

V D Bhandakkar*, VA Tabhanct & Sharda Ghosh*

*Department of Electronics, Anand iketan College, Warora 442 914

·;·Reader in Physics, Institute of Science. Nagpur

·:' Reader in Physics, V M V, Amravati

Received 20 May 2002; accepted 6 August 2003

The velocity of ultrasonic waves ( 10 MHz) for different compositions of mixtures or methanol. cyclohexane and Jl­

dioxane with acrolein and cinnamaldehyde has been measured in the temperature range I 0-40 oc. The excess compressibility p"E and excess molar volume 0 parameters have been discusseJ in the light of inter-molecu lar AB interactions and resulting disorder in these mixtures. It is observed that excess parameters ~ ,( and 0 can be used for classification or al l types or molecular interactions in binary liquid mixtures.

I Keywords: Ul trasonic waves, Binary liquid mixtures, Methanol , Cyc lohex:111e, p-dioxane, Acro lein , Cinnamaldehydc. Excess compressibility. Excess molar volume]

1 Introduction

Ultrasonic parameters are being used ex tensive ly to study molecular interaction in pure liquids 1

, binary and ternary liquid mixtures\ and ionic interactions in single mixed salt solutions3

.4 A departure from linearity in the velocity versus compos iti on behaviour in liquid mixtures is taken as an indication of the ex istence of interaction between the different species. However, it is seen that a representati on in terms of the observed paramete rs, such as velocity of ultrasonic waves, has a limited utility. Such a representation does not provide any information about the nature and the relative strength of the various inter-molecular interactions. On the other hand , a number of theoretical and experimental investigat ions' ·6 have shown that a representation in terms of the derived parameters,

such as adiabatic compressibility(~ "), van der Waals parameters (h) and their derivatives , such as ~ "E' bF, etc. from those obtained from the additive rule, provide a bette r insight into the inter-molecular processes. This paper presents the results of an ultrasonic study of mixtures of methanol cyclohexane and p-dioxane with acrolein and cinnamaldeh yde. Though a few investigations are available in the preparation on some of liquids

studied here, no comprehensive ultrasonic stud y has yet been reported.

2 Experimental Details

The liquids used were of BDH Ana lar grade and distill ed thrice before use, the middle fraction being taken in each case. The mixture was prepared at

25°C, immediately before use, by mtxtng appropriate volumes of the constituent I iquids taken correct to 0.1 ml , the total volume being about I 00 mi. The ultrasonic velocity was measured at I OMHz by the Ultrasonic Time Intervelomete r UTI­I 0 I (Innovative Instruments , Hyderabad) in the

temperature range I 0-40 °C, for acrole in + methanol, acro lein + cylohexane, acrole in + p­dioxane, cinnamaldehyde + methanol, cinnamaldehyde + cyc lohexane and cinnamaldehyde + p-dioxane, respective ly. The consiste ncy of the osci ll ator frequency was checked , using a digital frequency meter and was found to be 4 in I 04

• The density of solution was measured by hydrostatic

sinker method in the temperature range I 0-40 °C and had an accuracy of I in I o~. A spec iall y designed and fabricated double-walled, metallic ultrasonic cell and glass cell along with 6 di git monopan balance achieved an accuracy o f I in I o~ g in density measurement.

850 INDIAN J PURE & APPL PHYS , VOL 4 1, NOVEMBER 2003

Table I - The observed ultrasonic veloci ties and densities of cinnarnaldehyde +methanol & acrolein + met hanol

Cin namaldehyde +Methanol Acrolein + Methanol

Uo clu rn/s p kg/1113 gp kl!lrn ' Uo du m/s p ko/m·' gp kg/m ' --u- --u - 0 b

M/s {) dTK M/s dT K dT K *10 E 3 dT K * 10 E 3

0.0 1480.15 -3.5 I 0 1.03505 - 1.630 1493.99 -3.997 0.9 1555 -2.230 0. I 1435.00 -3.333 1.03350 -2. 140 1493 .50 -4.050 0.90600 -2 .150 0.2 1387.50 -3.080 1.0 1400 -1 .920 149 1.50 -4.125 0.89650 -2 .070 0.3 1375.02 -3 .833 0.97900 - 1.620 1490.25 -4.375 0.87850 - 1.700 0.4 1330.00 -3.330 0.96900 - 1.920 1489.25 -4.635 0. 87 150 - I . 160 0.5 1297.50 -3.mn 0.94800 -1.780 1468.86 -5.125 0.85850 - 1.526 0.6 1275.11 -2.903 0.92150 -1 .670 1460.00 -5.000 0.8495(1 -1 .450 0.7 1260.06 -3.53 1 0.91550 - 1.670 1408.75 -4.375 0.841~.0 -1.466 O.X 1247.50 <U43 0.86450 - 1. 100 1337.50 -3.500 0.82900 -1 .300 0.0 I 192.50 -2.750 0.83650 . 1. 170 1305 .00 -4.166 0.8 11 50 -1 .0 10 I .0 II X0. 15 -3. 140 0.80303 -0.950 11 80. 15 -3.140 0.80303 -0.950

Table 2- The oh~ervcd ultrason ic velocities and densities or cinnamaldehyde + cyclo hexane & acrolein+ cyclohcxane

Cinnarnaldehyde + Cyclohexatw

ll o du m/s p kg/m' gp kg/nf' --u- 0 -M/s ciTK * 10 E 3 dT K

0.0 14!:\0. 15 -3.5 10 1.03505 - 1.630 0.1 14'13.00 -3.200 1.01!:\80 -1.!:\37 02 1470.00 -3.220 I .00200 -2.000 0.3 1467.50 -3.3 16 0.98350 -2. 100 0.4 1462.00 -3.857 0.95700 - 1. 880 0.5 1454.50 -4.300 0.93250 -1.810 0.6 1448.50 -5.000 0.90000 - 1.627 0.7 1437.50 -5.000 0.87550 -1.41 0 CUI 1392.50 -4.250 0.85200 -1.250 0.9 138 1.00 -4.200 0.82900 - 1.200 1.0 I 372.00 -4.400 0.79800 -0.860

The temperature of the so lut ion was mainta ined constant to 0.1 °C using as ultra thermostat U-1 0. T he so luti on was stirred by mov ing the re fl ector and the sinker up and down.

Parameters ~ -· and V were obtai ned using standard relations . The excess parameters ~ "E and excess molar volume VE are given by the difference between the observed and the theore tical (s imple add iti ve rule) val ues of respective parameters. The error for eac h of the excess parameters was es timated and the deviations from addi ti ve law were fo und outs ide the limit o f e rror ( ::::::3 %).

Acro lein + Cyc lohexane

Uo clu m/s p ko-!m' gp kg/nr' --u - () b

M/s dTK * 10 E 3 ciT K

1493.99 -3.997 0.91555 -2.230 1482.00 -4.064 0.91000 -2.330 1471.00 -4. I 18 0.89250 -I .990 1459.00 -4.172 0.87650 -1.749 1446.00 -4.224 0.86800 -1.720 1432.00 -4.280 0.85550 - 1.575 1422.00 -4.332 0.84450 -1.469 14 10.00 -4.386 0.83105 -1.267 1402.00 -4.440 0.82000 -I .1 43 1338.00 -4.492 0.81000 -1.036 1372.00 -4.440 0.79800 -0.860

3 Result and Discussion

The observed ultrason ic velocities and densiti es o f pure liquids and binary mixtures with methanol solu te are given in Table I, cyc lohexane so lu te in Table 2 and p-dioxane so lute in Table 3. Fig. I shows the vari ati on of percentage excess compressibility and exce. s vo lume of p-dioxane+ c innama ldehyde, and acroiein + cy lohexane. Fig. 2 shows the variat ion for methanol + cinnamalde hyde, cyc lohexane+ci nnama lclehyde, methano l + acro le in and p-dioxane + acro le in . The observed ultrasonic velocity and dens ity variation with co mpos ition is found to be non-linear and thi s indicates the presence of hetero-molecular weak AB inte raction.

BHANDAKKAR et a i. :BINARY LIQUID MIXTURES 85 1

Tab le 3-The observed ul trasonic velocities and densities or cinnamaidehyde + p-dioxane & acrolein +p-d ioxanc

Cinnamaldehyde + p-dioxane

X ull du m/s p kgfm' gp kglm' --,1- II ~

M/s dTK * 10 E 3 dT K

0.0 14~0. 1 5 -3 .510 1.03505 - 1.630 0.1 1477.00 -3.286 1.04050 - 1.646 0.2 1476.30 -3.360 1.04150 - 1.560 0.3 1472.00 -3 .294 1.04750 - 1.630 0.4 1470.00 -3 .333 1.050 I 0 - 1.600 0.5 1468.00 -3 .354 1.05 140 - 1.480 0.6 1464.50 -3.4 12 1.05200 - 1.348 0.7 1462.00 -3.500 1.05320 - 1.298 0.8 1458.50 -3.660 1.05400 - 1. 167 0.9 1454.50 -3.850 1.05480 - 1.056 1.0 1450.97 -4.244 1.05700 -0.986

Thi s presence of hetero-molecular AB interac ti ons is re fl ected through the excess molar parameters,

such as, excess compressi bility, ~ .. E excess molar vo lume \_IE and excess VOW parameter bE. Excess bE has been fo und to have the same variation as \_IE and so. the plots are not inc luded . Hence, fo r understanding the nature and strength of the hetero­

molecul ar interacti ons, onl y two parameters ~.E and \_IE are considered s imultaneously.

4 Broad Classification of Molecular Interactions

A broad c lass ificati on of molecul ar interactions is presented be low:

Sr. 0 . pE "

vE "

Negative egative 2 Positive Positive 3 egative Positive 4 Positive egative

4.1 Case-1: ~ "E < 0 and V' < 0

As ve loci ty of ultrasonic waves is a sens1t1 ve functi on of space-filling factor, small changes in vo lume cause s igni ficant changes in ve locity of ultrasoni c waves . The volume of the liquid mixture depends upon the structu ral arrangement in liquid as well as on inter-molecul ar interac tions. The forces between the molecul es and also their geometry would dec ide the structura l arrangement. Thus, the geometry of molecules has a vita l ro le in dec iding the volume of a liquid . In a mi xture of two liquids, the shapes of the molecules. i.e. c luster geometry or

Acrolein + p -dioxane

U11 du m/s p kgjm·~ Q_p kglm' --,)- II ~

M/s dT K * 10 E 3 dT K

1493.99 -3.997 0.9 1555 -2.230 1493 .50 -3.984 0.92740 -2. 120 1489.00 -4.058 0.94200 -1.998 148 1.00 -4.082 0.95650 -1.853 1480.00 -4. 104 0.97200 -1.754 147 1.50 -4. 128 0.97820 -1.345 1467.00 -4.152 0.99400 -1.266 1465.00 -4.174 1.00920 - 1. 174 1460.00 -4.198 1.02340 -1 .030 1450.50 -4.222 1.03800 -0.927 1450.97 -4 .244 1.05700 -0 . 9~6

macro-geometry, would therefore, predominantl y, decide an excess of molar vo lume. An increase in the strength of the hetero-molecular fo rces manifesting in a decrease 111 adi abatic compress ibili ty ~ .. of the mi xture would tend to reduce the size of the cluster, hence decrease in total vo lume of the mi xture .

The vari ation of both ~ .. E and \_IE is non-linear with at least one minimum. Such smooth vari ation with minimum of certa in composit ion is known to indicate an attracti ve hetero-molecular AB interaction, leading to associ ati on of the molecules. Let the pure liquid A and B be represented as:

(A) liq . = (A, A .A, A.A .A, __ __ )

(B) liq. = (B,B .B, B .B .B ., _ _ __ )

i.e. a set of monomers, dimers, trimers, e tc. Due to an assoc iati ve hetero-molecul ar AB interacti on, the mi xture can be:

(AB) mi x = (A.B., A.B.B .,A.A.B, ____ )

Two minima will be obta ined fo r two re lative ly stable c lusters. The process leading to the stable clusters would be in equilibrium at these concent rati ons, respective ly.

The above assoc iation would occur due to the presence of an acti ve subgroup in A type and an acti ve subgroup in B type molecul es. If minima is closer lo higher concentrati on of A then, AA > BB, while a symmetrical variati on would indicate AB >

~52 lNDlAN J PURE & APPL PHYS, VOL 4 1, NOVEMBER 2003

AA as well as AB > BB as the re lative strength of interactions.

-2 ·0

p-DIOXANE + ~lt'JNAMALDEHYDE . ___..,

CYGLOHEXANE + ACROLEIN • -- -. - em

0-2 0-L, 0·6 0·[l

0·2 Cm

0·4 0·6 0·8

I •

J Fig. I - Variation of % 0 and o/r 0} with respect to composition (em) of ji·dioxane + cinnamaidehyde & cyclohcxanc + acrolein

4.2 Case- II: ~"E > 0 and VI'> 0

An increase in ~}' denotes the weakening of the inter-molecular interactions . The hetero-molecu lar AB interactions not only disturb the homo­molecular AA, BB interactions in componen ts liquids, but also cause a rearrangement in the geometry of the cl usters. Jf the geometry were suc h that. the vol ume of clu sters increases, it would lead to an increase in vo lume of the mi xture, i.e. excess mola r vo lume would be positive. The dissoc iation taki ng place tn component liqu id would be represented as:

n.A, - - - - - -> m.A, , i > j

~f•Pc E

Cm 0·2 0 ·4 0-6 0·8 6 ·o 1-~-....::___:::._::_ _ _:::_:>__.._.,

5·0

\ \

\

\ 2·0

r , ..• ,.. .. \ ::.,·" __ J,.. .... - · !;, ........ ~ - ..... \ 1-0

................

METHANOL+ CINNAMALDEHYDE CYCLOHEXANE + CINNAMALDH-iYDE METHANOL +ACROLEIN p-DIOXANE +ACROLEIN

0-2 0·4

-2. ' '" ' '

-4 ,.,.

\

-e. •

- 8

-1 0

-12

- 14

-16

-18

-20

' '

0·8

• I ,.

' 4 I ... .._Iff

I

f:..- -·-.0.

Fig. 2 - Variation of % VE and % ~"E wi th respect to composi tion (em) of methanol + cinnamalclchyde. cyc lohexane + cinnamaldehyde, methanol + acrolei n and p-diox~me + acro lein

BHANDAKKAR et ai.:BINARY LIQUID MIXTURES 853

The dissociation would predominantly occur in one of the component liquids in which homo­molecular interaction is extremely weak as compared to the hetero-molecular interactions . One may be in a position to identify the dissociating

component from the ~"E and yE variation with composition of liquid A and B, the maximum occurring for the higher concentration of the component.

The dissociation is m:lXimum where there is

maxima 111 ~ "E function, and the dissociated component takes maximum inter-cluster spacing at that concen tration . For two maxima, the total process is a sum of two dissociative processes. These processes are exactl y an inverse of associative process, but here, it is the A orB type of molecular cluster, which dissociates and not AJBJ type.

4.3 Case- III: ~"E < 0 and V1l > 0

In this case, an observed decrease in ~/ indicates an attractive hetero-mo lecu lar interaction, leading to an association between these molecules. An observed increase in yE (along with negative ~.E) shows, using Schaaffs relation, an increase in b the occupied molar volume. This may be due to presence of clusters of types AB ----- AB ------ AB over AB . The reason for increase in volume may be due to the larger size of the molecular clusters. The size of the cl uster AB--------AB-------AB would however depend upon whether the hetero-molecular interactions are of short range or relatively long range. Interaction of short range would lead to c lusters of smaller size, while long range interactions producing, ordering in cluster would lead to large s ize of clusters. An observed increase in vo lume wou ld also be due to ordering in clusters. The relative importance of the above processes in mixture depends upon the nature of the component molecules :md would show themselves in shapes of the excess ad iabatic compressibility and excess molar vo lume var iations.

4.4 Case- IV: ~"E > 0 and V1l < 0

An observed ~ .E indicates a hetero-molecular interaction tending to destroy the weak AA and BB interactions . The loosening of homo-molecular interactions does not lead to an increase in size of the respective cluster. but its complete destruction. The negative V: shows that the molecules , which are

set free from the original clusters, now occupy interstitial, free space in the cl usters, which are not broken, without appreciably increasing their size. The .concealment of one type of molecules (of one component) in the clusters of the other type may be imagined to occur, leading to a decrease in the total volume of the mixture. The rate of br~aking up to the weaker clusters would be reflected in the shape of ~ "E and VE variations with compositions.

The broad discuss ion given above regarding the

variation of ~/ and yE shows that, these variations not only indicate the presence of hetero-molecul ar AB interactions in liquid mixtures, but also provide information on the relati ve strengths of homo­molecular AA and BB interact ions. When the AB interactions are comparab le or slightly stronger than both AA and BB clusters forming AB clusters as indicated by a decrease in ad iabatic compressibility and diminished volume of the mixtures. When AB interaction is much stronger than AA and BB interactions, it may not lead to formation of AB clusters but also ordering in the c lusters, g iving rise to AB----AB----- of larger size givi ng an increase in volume of the mixtures.

When AA and BB interactions in component liquids are of comparable strength and AB interaction is sl ightly weaker, then it does not lead to a disruption of AA an BB clusters, but only gets loosened. AA and BB interactions leading to an increase in the size of the respective clusters result in increase in volume of the mixtures. However, when AB interactions are stronger than the other, it causes a complete disruption of the weaker clusters but stronger c lusters remain intact. Molecules released from the disrupted cluster may occupy interstitial spaces in the intact clusters leading to a concealment of free molecules , resulting in the reduction of total volume of the liquid. Thus, the observed excess compressibility ~ .. c considered along with observed excess volume V: provide an insight into the relative strength of the inter­molecular interactions in liquid mixtures.

5 Discussion of the Systems

The systems p-dioxane + cinnamaldehyde and cyclohexane + acrolein falls under the ease-l of broad classification where both ~ "E and yE are negative. In both the systems, ~ .• E curves are symmetrical (Fig. I ). The re lati ve stre ngth of AB interaction in p-dioxane + cinnamaldehyde is greater

~54 INDIAN 1 PURE & APPL PHYS, VOL 4 I, NOVEMBER 2003

than cyc lohexane + acrolein. [n case of cyc lohexane +acrolein AB interaction is greater than AA and BB interaction as cyc lohexane is non-pol ar liquid and ac ro lein is polar liquid with dipole moment 2.90 D. Hence, AB interact ion in these systems are induced clipolc-clipole type. The other sys tem p-clioxane + cinnamalclehycle has more depth as compared to cyc lohexane + ac role in , and also found to be symmetrical. Therefore, AB inte raction is stronger than AA and BB interaction . Since clip is concentrated on A side of molar concentration , AA interaction seems to be stronger than AB and BB interactions.

The systems methanol + cinnamalclehyde, cyc lohexane + c innamalcle hycle, p-dioxane + acrolein and methanol + acrolein falls under the

case-HI of the broad classification , where. ~ .. E < 0

and yE > 0. The observed negat ive ~ .. E denote the decrease in adiabatic compressibility than the observed compressibility . This indicates the presence of hetero-molecular AB interactions in all the sys tems resulting in formations of clusters .

The re lative strength of AB in te rac tion decreases in the order, methanol + acrolein, cyc lohexane + cinnamalclehycle, methanol + cinnama lclehycle and p-clioxane + acrolein. ln methanol + acrolein, the strength of AB interact ion is greater than other systems. In all the systems, the

nature of ~ ,." curves are symmetrical which cause overa ll increase in vo lume. Since, all ~ .. E curves are smooth, the AB interactions are indicated in all the systems. In methanol + acrolein and methanol + cin namaldehyde, the dip concentrated towards A side, indicates AA inte raction is stronger than AB and BB inte ract ions. On the other hand , in the system cyclohexane + cinnamaldehyde, the dip concentrated toward 8-side, indicating BB interaction is stronger than AB and AA inte ractions. A cluster may form in all the systems resu lting in an

increase in volume of mixture in the order, methanol + acrolein, p-dioxane + acrolein, cyc lohexane + cinnamalclehyde and methanol + c innamaldehyde .

6 Conclusions

(a) Molecular interaction 111 any binary liquid system can be interpre ted under the broad classification outlined in this paper.

(b) The hetero-molecular AB interaction is present in all systems investigated.

(c) The dipole-induced-dipole and dipole-dipole interactions are found to be responsible for the observed hetero-molecular interaction 111 the systems.

(d) The re lative strength of hetero-molecular AB interaction in the system investigated decreases in the order of methanol + acrolein, cyclohexane + cinnamaldehyde, methanol + cinnamaldehyde, p­dioxane + cinnamaldehyde, cyclohexane + acrolein, and p-dioxane +acrolein, respectively.

(e) The AB interaction does not lead to complex formation in any of the systems.

(f) The systems investigated are classified in ease-l and case-ill of broad classification outl ined in the paper, where, (a) yE and ~.E both are negative and (b) yE is a positive and ~ .. E is negative.

References

Sheshagiri Rao M C, Indian J Pure & AtJfl/ Phys, 9 ( 197 i) 169.

2 Tabhane V A, Indian J Pure & Appl Phys, 23 (I n3) 155.

3 Shivkumar K V, Reddy K L & Subramanyam S V, Z Phys Chem. 83 ( 1973) 141.

4 Tabhane V A & Patki B A, Indian J Pure & Appl Phys, 23 ( 1985) 58.

5 Singh D P & Bhatti S S, Acoustiw, 56 ( 1984) 290.

6 Dclmos & Turrucll , Trans Faraday Soc, 70 ( 1975) 590.