International Journal of Recent Innovation in Engineering and Research Scientific Journal Impact Factor - 3.605 by SJIF e- ISSN: 2456 2084 ULTRASONIC STUDIES ON MOLECULAR INTERACTIONS IN THE BINARY MIXTURES OF METHYLBENZOATE WITH N- ALKANOLS AT 303 K T.Sumathi 1 and S.Vasanthi 2 1,2 Department of Physics, Annamalai University, Annamalai nagar-608002, Tamilnadu, India Abstract- The ultrasonic velocity(u), viscosity( ) and density( ) have been measured for the binary mixtures of methylbenzoate with propanol and butanol at 303K. The experimental data have been utilized to calculate the various acoustical parameters such as adiabatic compressibility ( ), free length (L f ), internal pressure ( i ) and acoustic impedance (Z). The various excess properties such as excess adiabatic compressibility ( E ), excess free length (L f E ), excess internal pressure ( i E ) and excess acoustic impedance (Z E ) were calculated. The results were discussed in terms of the existence of intermolecular interactions between the components in the liquid mixtures under the study. Keywords- 1 alkanol, Binary liquid mixture, excess values, molecular interaction. I. INTRODUCTION The study of molecular interaction in binary and ternary liquid mixtures plays an important role in the development of molecular sciences. In recent years, ultrasonic method has become a powerful tool in providing information regarding the physico-chemical properties of liquid system [1,2]. Ultrasonic wave propagation affects the physical properties of the medium, and hence, can furnish information about molecular interactions of the liquid and liquid mixtures [3,4]. Further, such studies as functions of concentration are useful in gaining insight into the structure and bonding of associated molecular complexes and other molecular processes. The variation of ultrasonic velocity and other ultrasonic parameters along with their excess values of binary liquid mixtures with changing mole fraction of one of the components has been investigated by many researchers [5, 6]. The derived acoustical parameters and their excess values provide a wealth of information to have better understanding of the structure of liquids and intermolecular interactions in liquid mixtures. The study of molecular association in binary liquid mixtures having alcohol as one of component is of particular interest since alcohols are strongly self-associated liquids having three dimensional network of hydrogen bonding and can be associate with any other group having some degree of polar attraction [7]. Methyl benzoate is used in perfumery also used as a solvent and as a pesticide, which is used to attract insects such as orchid bees. Propanol is formed naturally in small amounts during many fermentation processes also used as a solvent in the pharmaceutical industry mainly for resins and cellulose esters. It is a small chain alcohol with three carbon atoms also used in the manufacture of various esters, perfumery and flavours [8]. Butanol is used as an ingredient in perfumes and as a solvent for the extraction of essential oils and the largest use of 1-butanol is as an industrial intermediate, particularly for the manufacture of butyl acetate. In view of the growing interest to analyze the physicochemical properties of liquid systems by ultrasonic methods, an attempt has been made to investigate the molecular interaction in binary systems of methyl benzoate with propanol and butanol at 303K. II. EXPERIMENTAL DETAILS In all systems, the various concentrations of the binary liquid mixtures were prepared in terms of mole fraction, such as 1 propanol with MB and 1 butanol with MB varied from 0.1 to 0.9. @IJRIER-All rights Reserved -2018 Page 15
The density of pure liquids and mixtures were determined using a specific gravity bottle by relative measurement method with reproducibility of 0.0001 g cm -3 (model SHIMADZU AX-200). An Ostwald s viscometer 10 ml capacity was used for the viscosity measurement of pure liquids and liquid mixtures and efflux time was determined using a digital chronometer to within 0.01 s. The speeds of sound waves were obtained by using an ultrasonic interferometer (Model F81) Supplied by M/S Mittal Enterprises, New Delhi, having the frequency of 3 MHz with an overall accuracy of 2 ms -1. An electronically digital operated constant temperature bath (RAGAA Industries, Chennai) has been used to circulate water through the double walled measuring cell made up of steel containing experimental mixtures at the desired temperature. The accuracy in the temperature measurement is 0.1 K. Theory The acoustical parameters such as adiabatic compressibility ( ), intermolecular free length (L f ), internal pressure ( i ) and acoustic impedance (Z) were determined using observed values of velocity, density and viscosity from the following equations [9]: 1 β (1) 2 U L f = K T 1 / 2 2 / 3 K πi brt 7 / 6 U M (3) U Where K T is the temperature dependent constant, K the temperature independent constant (K = 4.28 x 10 9 ), b a constant which is 2 for cubic packing. R the gas constant and T is the temperature in K. U and are velocity and density of liquids. The excess parameters (A E ) of all the acoustic parameters were computed by the relation: A E - = A exp A id (5) Where A id = Ai X i. n i 1, A is any acoustical parameter and X i the mole fraction of the liquid component i i III. RESULTS AND DISCUSSION The experimental values of density, viscosity and ultrasonic velocity at 303 K of all pure liquids are presented in Table 1 and the same for the binary system I and II are listed in Table 2. The calculated values for various acoustical parameters such as, L f, i and Z are given in Table 3. The density and ultrasonic velocity of the binary liquid mixtures are decreasing with increasing mole fractions of 1-ols in both the systems whereas, the viscosity increases with increase in mole fraction of 1-ols (Table 2). As a number of hydrocarbon groups or the chain-length of the alcohol increases, a gradual decrease in sound velocity was observed. The adiabatic compressibility ( ) (Table 3) increases as the mole fraction of 1-ols increases. In these systems, the increase in adiabatic compressibility with the rise of concentrations of 1-ols indicates the weakening of inter molecular interaction [10]. Based on the model for sound propagation proposed by Eyring and Kincoid [11], ultrasonic velocity should increase, if the inter molecular free length decreases and vice versa. This fact was observed in the present study for all the binary liquid systems. Same trend was noticed by earlier workers [12,13] in their liquid mixtures. It is found that the free length (L f ) (Table 3) increases with increase in mole fraction of 1-ols and it is due to expansion, which indicates the lesser packing to the molecules hence the intermolecular cohesion is weaker leading to weak molecular association [14]. Available Online at: www.ijrier.com Page 16
From the Table 3, it is observed that the internal pressure ( i ) increases with increasing concentration of 1-ols. It is due to the fact that, at lower mole fractions the interactions are found to be strong and hence it is of cohesion in nature. However, it becomes adhesive with the addition of 1- ol. The magnitude of the adhesion increases with increasing mole fraction of 1-ols [15]. The i increases due to the various degrees of dispersive interaction and the coloumbic interaction existing between the component molecules [9]. TABLE: 1. Values of density (ρ), Viscosity (η), and velocity (U) of Pure liquids at 303K Liquids ρkgm -3 η x 10 3 NSm -2 U ms -1 I-Propanol 796.27 1.7591 1201.8 I-butanol 801.20 1.9753 1225.3 Methyl Benzoate 1062.84 1.1864 1365.4 TABLE: 2. Values of density (ρ), Viscosity (η), and velocity (U) of systems I and II at 303K Mole fractions ρkgm -3 η x 10 3 X NSm -2 1 X 2 U ms -1 System I: 1-Propanol + Methyl Benzoate 0.1002 0.9002 1062.84 1.1864 1365.4 0.2000 0.8002 1041.98 1.1884 1346.6 0.3001 0.7002 1020.68 1.2114 1344.4 0.4005 0.6001 999.45 1.2188 1326.2 0.5001 0.5001 975.49 1.2192 1309.8 0.6001 0.4002 947.49 1.2253 1292.5 0.7002 0.3001 914.49 1.2301 1271.8 0.8000 0.2001 882.59 1.2940 1241.0 0.9001 0.1000 842.67 1.3592 1223.3 System II: 1-Butanol + Methyl Benzoate 0.1000 0.9000 1052.56 1.4254 1369.7 0.1999 0.8889 1031.24 1.4293 1353.0 0.3000 0.7001 1006.91 1.4649 1341.6 0.4000 0.6000 897.48 1.4767 1330.9 0.5001 0.5000 880.07 1.4797 1312.1 0.5999 0.3999 867.52 1.4871 1300.5 0.7001 0.2999 840.69 1.4937 1274.8 0.7999 0.2001 839.64 1.5091 1259.1 0.9000 0.0996 819.48 1.5378 1242.8 TABLE: 3. Values of Adiabatic compressibility ( ), Free length (L f ), Internal pressure ( i ) and Acoustic impedance (Z) of system I and II at 303K Mole fraction x 10 10 pa -1 L f 10 10 m I x 10-6 Z x 10-6 pa X kgm -2 S -1 1 X 2 System I: 1-Propanol + Methyl Benzoate 0.1002 0.9002 5.047 0.4482 350.1 1.451 0.2000 0.8002 5.293 0.4590 373.1 1.403 0.3001 0.7002 5.421 0.4646 402.0 1.372 0.4005 0.6001 5.689 0.4759 434.0 1.325 0.5001 0.5001 5.975 0.4877 469.0 1.278 0.6001 0.4002 6.318 0.5015 510.0 1.225 0.7002 0.3001 6.761 0.5188 557.3 1.163 Available Online at: www.ijrier.com Page 17
0.8000 0.2001 7.357 0.5412 632.4 1.095 0.9001 0.1000 7.930 0.5619 716.7 System II: 1-Butanol + Methyl Benzoate 0.1002 0.9002 5.064 0.4501 347.6 1.442 0.2000 0.8002 5.297 0.4592 371.9 1.395 0.3001 0.7002 5.518 0.4687 392.7 1.351 0.4005 0.6001 6.290 0.5004 418.1 1.194 0.5001 0.5001 6.324 0.5045 444.8 1.155 0.6001 0.4002 6.816 0.5209 476.4 1.128 0.7002 0.3001 6.962 0.5286 509.2 1.072 0.8000 0.2001 7.576 0.5492 554.7 1.048 0.9001 0.1000 7.994 0.5628 608.7 1.018 Further the acoustic impedance (Z) is decreased with increasing mole fraction of 1-ols. This decrease in acoustic impedance indicates significance interaction between the component molecules [16]. In order to substantiate the presence of interaction between the molecules, it is necessary to study the excess parameters [9]. The deviation of the physical property of the liquid mixtures from the ideal behaviour is the measure of interaction between the molecules, which is attributed to either adhesive or cohesive forces. The values of excess adiabatic compressibility ( E ) (Fig.1) and excess free length (L f E ) (Fig.2) changes from negative to positive as the mole fraction of 1-ols increases. The same trend was observed in Nikam et al., (2000) and Ali et al., (2002) [17-18]. According to Roshan Abraham et al., (1996), and Nikam et al., (2000) [17,19] the negative E and L f E is an indication of strong intermolecular interaction in liquid mixtures, which is attributed to charge transfer, dipole-induced dipole, while negative sign indicates weak interactions, which results from dispersion forces, interstitial accommodation and orientation ordering lead to a more compact structure. The positive E and L f E arises due to breaking of H-bond in the self associated alcohol. FIGURE.1: Excess adiabatic compressibility Vs. Mole fraction for the system I & II at 303 K Available Online at: www.ijrier.com Page 18
FIGURE. 2: Excess free length Vs. Mole fraction for the system I & II at 303 K Fig.3 shows the variation in excess internal pressure ( i E ) verses the mole fraction of alcohols in the binary systems. The addition of 1-o1 makes the i E to be negative at lower mole fraction and it become positive as we increase the concentration of 1-ols. The addition of OH group disturbs the molecular symmetry and this forms a strong repulsive type interaction to the structure breaking. The effective cohesive is highly reduced and it becomes adhesive in nature. This leads to negative and becomes increasively positive trend of i E with increasing mole fraction of 1-ol [20]. It indicates that the interactions are weakening from the strong interactions. The excess acoustic impedance is positive for the lower mole fraction, whereas, on increasing the concentrations of 1- ols, Z E changes from positive to negative (Fig.4). An increasingly negative value of Z E with mole fraction is indicative of the decreasing strength of interactions between component molecules of the mixture [21]. FIGURE.3: Excess internal pressure Vs. Mole fraction for the system I & II at 303 K FIGURE. 4: Excess acoustic impedance Vs. Mole fraction for the system I&II at 303 K IV. CONCLUSION The results of the present study indicate that the thermodynamic parameters are sensitive to the molecular interactions present in the liquid mixtures. The strength of associative interaction Available Online at: www.ijrier.com Page 19
between the unlike molecules weakens with the increase in chain length of the 1-alcohols and the order of interaction is as follows; 1- propanol > 1-butanol. This is due to hetero association and homo association of molecules decrease with increasing chain length of carbon atoms in alcohols, probably due to less proton donating tendency of higher alcohols. REFERENCES [1] Paikaray, R. and Mohanty, N. 2013. Evaluation of thermodynamical acoustic parameters of binary mixture of DBP with tolune at 308 K and at different frequencies, Research journal of chemical science, 3 (5), 71-82. [2] Mistry, A.A. and Bhandakkar, V.D and Chimankar O.P. 2012. Acoustical studies on ternary mixture of toluene in cyclohexane & nitrobenzene at 308 K using ultrasonic technique, Journal of chemical and pharmaceutical research, 4(1), 170-174. [3] Ernest, S. and Kavitha, P. 2011. 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