Relaxation Analysis on Liquid Mixture of Ethylene Glycol / Diethylene Glycol and Benzonitrile in Benzene

 

M. Subramanian¹, G. Parthipan²

¹Dean, Fatima Michael College of Engineering and Technology, Madurai, Tamil Nadu, India

²Department of Physics, Vel Tech Multi Tech DR Rangarajan DR Sakunthala Engineering College,

Avadi, Chennai - 600 055. Tamilnadu, India

 

ABSTRACT:

The permittivity and the dielectric loss of ternary mixtures of equimolar concentrations of ethylene glycol / diethylene glycol with benzonitrile in benzene have been measured at 8.33GHz at 35 ^°c. The permittivity and the dielectric loss have been plotted against concentration in wt. fraction. The slopes of these straight lines have been used for complex plane plots (” vs. ’). The complex plane plots are Cole- Cole arcs. The distribution parameter (a), the most probable relaxation time( t ), the relaxation time for overall rotation of the molecule , the relaxation time for group rotation  and the excess dipole moment () for various systems have been calculated by Cole-Cole and Higasi’s methods. Data has been analyzed in terms of two-relaxation processes (i.e.) contribution from overall rotation and group rotation

 

INTRODUCTION:

Relaxation studies are of great help in understanding the molecular dynamics of molecules [1-3]. There is a lag in the attainment of equilibrium in an electric field of very high frequencies and dielectric relaxation occurs which in general may be defined as the lag in the response of a system to change in the forces to which it is subjected. This dielectric relaxation leads to an anomalous dispersion of dielectric constants, which decrease, with increase of frequency. Hence, the study of dielectric relaxation would give information on the fluid structure. Debye [4] deals with the problem of dielectric relaxation as the time lag experienced by a dipolar molecule to orient itself to the high frequency field direction against the viscous forces of its surroundings. The relaxation times of liquid dependents the functional groups and the volume of the molecules.

 

So it may be appreciated that the relaxation times of molecules have a large influence on the dielectric parameters. Chaube et al reported the relaxation studies of binary mixture of diethylene glycol and methanol [5]. Sengwa et al have attempted a comparative studies on ethylene glycol, propylene glycol and diethylene glycol [6]. S.C Mehrotra et al also studied molecular interaction of binary mixtures of ethylene glycol and Dimethysulfoxide[7]. V.A.Rana et al carried out the dielectric relaxation and dispersion studies of mixtures of 1-propanol and benzonitrile in pure liquid state at radio and microwave frequencies [8].A.D.Vyas et al made an attempt for Dielectric relaxation study of 1-propanol, benzonitrile and their mixtures at microwave frequency [9]. In this paper we are reporting the relaxation and viscous mechanism for the following ternary systems. System .1 Ethylene glycol + benzonitrile in benzene System.2 Diethylene glycol + benzonitrile in benzene Ethylene glycol is primarily used in antifreeze formulations and it has behavior to disrupt the hydrogen bonding when mixing with some liquids. In pharmacy side, ethylene glycol liquid is used to avoid the side effect of other compound Diethylene glycol is used to make up the unsaturated polyester resins, polyurethanes, and plasticizers. DEG is a solvent for resins, oils nitrocellulose, dyes and other organic compounds. Further it is also used as wallpaper strippers, artificial fog, brake fluid, lubricants, and personal care products. Benzonitrile is, aromatic organic compound, a useful solvent and a versatile precursor to many derivatives. The benzonitrile ligands are readily displaced by stronger ligands and benzonitrile complexes used as synthetic intermediates

 

MATERIALS AND METHODS:

The static dielectric constants were measured at 1 KHz using VLCR-7 meter supplied by Vasavi Electronics, India [10]. e_¥  was taken as the square of the refractive index (n_D), which was measured by Abbe¢s refractometer[11]. Densities were determined using a 10 ml specific gravity bottle and a K-Roy microbalance. The liquids were BDH AnalaR variety purified by standard methods. All measurements were made at 35 ^°c and the temperature was controlled within ±0.5^°c by a thermostat. The uncertainties in the measurements of dielectric constants and refractive indices were ±0.0005 and ± 0.0002 respectively. X-band test bench is used to measure the dielectric constant ana dielectric loss of liquids. K-27 Klystron, supplied by the Scientific Instrument Co. Ltd., Allahabad was used as the source for microwave power at 8.33 GHz. The temperature of the liquid inside the cell was kept constant by circulating water around it from a thermostat [12].

 

THEORY:

 Resonance circuit methods, transmission line methods, impedance bridge methods and free space techniques are the methods used to measure dielectric constants at microwave frequencies. Hill et al. [13] critically analyzed the merits and demerits of the above methods. In the present study, transmission line method using wave-guide technique is employed. To measure dielectric constant and dielectric loss of the solutions of polar liquids in non-polar solvents, Smyth et al. [14] have described a

In the present investigation, both Cole-Cole and Higasi’s methods have been used to calculate a and t . This will enable us to study quantitatively the relaxation mechanisms involved in the case of solutions of alcohols and nitriles.

RESULT AND DISCUSSION:

The values of the dielectric constants at high frequency (e’), the dielectric loss (e”), the distribution parameter (a), the most probable relaxation time (t), the relaxation time for overall rotation of the molecule , the relaxation time for group rotation  and the excess dipole moment for various systems are reported in Tables 1 and 2. Higasi’s parameters were calculated using Eq. ( 11 ). Relaxation time (t ) and the distribution parameter ( a ) were also determined by Cole-Cole method using Eq. ( 10 ).

 

Table 1:- Values of various dielectric constants and Higasi’s parameters at 308K

System	X2	eo	e¥	e’	e”
Ethylene glycol +	0.05	2.7892	2.0475	2.6885	0.1616	11.9442	0.8675	9.9303	3.2319
benzonitrile in benzene	0.06	2.8125	2.0486	2.7013	0.1688	10.3413	0.742	8.489	2.8136
	0.07	2.8358	2.0498	2.7143	0.1762	9.1964	0.6524	7.461	2.5165
Diethylene glycol +	0.05	2.859	2.0469	2.7427	0.185	13.3404	0.856	11.014	3.7097
benzonitrile in benzene	0.06	2.8823	2.048	2.7538	0.1929	11.5048	0.7325	9.3626	3.2145
	0.07	2.9056	2.0495	2.7671	0.2006	10.1937	0.6483	8.2164	2.8663

 

Davidson [16] showed that the relaxation process for any system can be resolved into the intermolecular relaxation time () and the intra molecular relaxation time () components only if the ratio of the two relaxation times  is greater than 6. In our present investigation, no such resolution is found to occur due to the increased overlap of two nearly equal regions. The different sizes of the relaxing units give rise to a changed environment, but not a distinguishable change in the multimeric unit responsible for different relaxation times. Our results are consistent with the interpretation that there is a progressive change in the n-mer and not any abrupt change on dilution. The interaction between the dipoles is also reduced by the solvent enabling the dipoles to rotate more freely. Similar results were reported by Dannhauser et al. [21] and Campbell et. al.[22]. t’ values obtained by Cole-Cole plot are lower than the values obtained by Higasi method. This may be attributed due to the non-rigid behavior of the solute molecules. It can be seen in Table 2

 

Table 2:- Values of various relaxation time, distribution parameter, and activation energy at 308K

 

The values of t are higher in diethylene glycol + benzonitrile mixture than in ethylene glycol + benzonitrile mixture. This may be due to the increased size of the diethylene glycol than ethylene glycol. Similar results are reported by Purohit et al. [23] for the mixture of diethylene glycol with monomethyl, monoethyl and monobutyl ether. Viscosity of benzonitrile is smaller than other aliphatic nitriles reported in my previous paper. Hence t for benzonitrile mixture of alchols in non-polar solvent is expected to have a value smaller than that of the mixtures with aliphatic nitriles. But t values for benzonitrile mixture of alcohols in non-polar solvents are greater than those of the mixtures of alcohols with aliphatic nitriles. This indicates that t is independent of the viscosity of the mixtures. Similar conclusions were drawn by Purohit et al. [23]. Due to the bulkiness of the solute molecules, t increases. increases with the chain length of the aliphatic alcohol present in the mixture irrespective of the aromatic nitrile present in the mixture. This may be due to the increase in the size of the molecules. Larger size of the molecules requires greater energy to lift a molecule over the potential energy barrier. Increase in the value of  decreases the probability of a jump from one orientation into another resulting in the increase in the value of the relaxation time. For mixtures with aliphatic nitriles, values of  increase with the bulkiness of the group In all the systems studied the free energy of activation of dipole orientation  is less than the corresponding value of the viscous force  for all the systems which is expected because viscous flow involves translation as well as rotational motion of the molecule, whereas dielectric relaxation process involves only rotational motion. The excess dipole moment is a qualitative index for the presence of hydrogen bond in the ternary systems. The dipole moment of the mixture is calculated using Eq.(9). The excess dipole moment is calculated using Debecker and Huyskens [24] equation  =  (18) The presence of a hydrogen bond between the nitrogen of the nitriles with the oxygen of the hydroxy groups of alcohols in these systems is indicated by the excess dipole moment values as reported by Shobanadri et al. [25]. The excess dipole moment may be attributed to the proton-transfer in this bond. The values of  are found to be negative for all the ternary systems. This shows the absence of ionic structures. The negative value of  also indicates the presence of hydrogen bonds between the partners [26].

 

CONCLUSION:

Dielectric relaxation behavior of the ternary mixtures of equimolar concentrations of ethylene glycol / diethylene glycol with benzonitrile in benzene has been studied along with viscometric studies. This investigation shows that t values for mixture of diethylene glycol and benzonitrile in non-polar solvents are greater than those of the ethylene glycol and benzonitrile . In all the systems studied the free energy of activation of dipole orientation  is less than the corresponding value of the viscous force  for all the systems. Negative values of dipolar increment are obtained for both systems, which imply nonexistence of ionic structures.

 

REFERENCES:

1.     Barthel J, Buchner R , Eberspächer P. -N, Münsterer M, Stauber J, Wurm B, (1998) Dielectric relaxation spectroscopy of electrolyte solutions. Recent developments and prospects. Journal of molecular liquids.1998;78:83-109

2.     Sengwa RJ, Kaur K (1999) Temperature dependent association and relaxation in monoalkyl ethers of ethylene glycol and of diethylene glycol in dilute solutions of benzene from static and complex microwave dielectric measurements. Journal of molecular liquids.1999; 82: 231-243

3.     Sengwa RJ, Madhvi Abhilasha.A comparative study of non-polar solvents effect on dielectric relaxation and dipole moment of binary mixtures of mono alkyl ethers of ethylene glycol and of diethylene glycol with ethyl alcohol.Journal of molecular liquids.2006; 123:92-104

4.     Debye, P., ‘Polar Molecules ‘, Dover, New York (1929).

5.      H. A. Chaube, V. A. Rana, P. Hudge, A. C. Kumbharkhane, Dielectric relaxation studies of binary mixture of diethylene glycol mono phenyl ether and methanol by Time Domain Reflectometry J.Mol.Liq.2015; 211:346-352

6.     Sengwa R J. Dielectric Relaxation in Ethylene Glycol - Dimethyl Sulfoxide Mixtures as a Function of Composition and Temperature. Journal of molecular liquids. 2003;108:47-60

7.     Undre P B,Khirade P W, Rajenimbalkar V S,Helambe S N,Mehrotra S C. Dielectric Relaxation in Ethylene Glycol - Dimethyl Sulfoxide Mixtures as a Function of Composition and Temperature. Journal of korean chemical Society.2012; 56:416-423

8.     A. N. Prajapati, A. D. Vyas, V. A. Rana, S. P. Bhatnagar, Dielectric relaxation and dispersion studies of mixtures of 1-propanol and benzonitrile in pure liquid state at radio and microwave frequencies, J. Mol. Liq. 2010;151:12-16

9.     D. G. rivedi, V. A. Rana, S. P. Bhatnagar, A. D. Vyas, Dielectric relaxation study of 1-propanol, benzonitrile and their mixtures at microwave frequency J.Mol.Liq.2006;129: 173-175

10.   Parthipan G, Thenappan T. Dielectric and thermodynamic behavior of binary mixture of anisole with morpholine and aniline at different temperatures. Journal of Molecular Liquids.2008;138:20-25

11.    Parthipan, G.; Thenappan, T. An investigation on the molecular dynamics of binary mixtures of anisole with acetic and propionic acids, J.Sol.Chem. 2007,36,1231-1242

12.   Subramanian M, The nappan T, Parthipan G. Dielectric relaxation in ternary systems of alcohols and nitriles in benzene at microwave frequency, Philosophical Magazine Letters.2008;88:889-895

13.   Hill N E, Vaughen W E, Price A H, Davies M, ‘ Dielectric properties and molecular behaviour ‘ , Van Nostrand, New York ( 1969

14.   Franklin A D, Heston W M. Hennelly Jr EJ, C.P.Smyth. Microwave Absorption and Molecular Structure in Liquids. V. Measurement of the Dielectric Constant and Loss of Low-loss Solutions, Journal of American Chemical Society. 950;72: 3443- 3447

15.   Cole K S, Cole R H. Dispersion and Absorption in Dielectrics I. Alternating Current Characteristics, Journal of Chemical Physics.1941; 9 :341-351

16.   Davidson D W, Cole R H, Dielectric Relaxation in Glycerol, Propylene Glycol and n-Propanol., Journal of Chemical Physics.1951; 19 :1484-1490

17.   Frohlich H, ‘Theory of Dielectrics’, Clarendon Press, Oxford (1958).

18.   Higasi K., ‘Dielectric relaxation and molecular structure’, Research Institute of Applied electricity, Sapporo (1961).

19.   Higasi K, Koya Y, Nakamura M.Dielectric Relaxation and Molecular Structure. V. Application of the Single Frequency Method to Systems with two Debye Dispersions, Bulletin of Chemical Society Japan.1971; 44 : 988-992

20.   Davidson D W. Dielectric relaxation in liquids: II. Isomeric pentanediols Canadian Journal of chemistry.1961; 39 : 2139-2154

21.   Dannhauser W, Guering R, Flueckinger A F. Dielectric properties of Liquid 2- Propen-1-ol and 2-Propyn-1-ol, Journal of Chemical Physics.1970; 52: 6446-6448

22.   Campbell C, Crossley J, Glasser L. Dielectric relaxation of some alcohols in solution ,Adv. Mol. Relaxation Processes.1976; 9: 63-77

23.    Purohit H D, Sengwa R J. Dielectric relaxation in mono alkyl ethers of diethylene glycol at microwave frequencies ,Journal of Molecular Liquids.1989; 40 :237-250

24.   A.N.Prajapati, V.A.Rana A.D.Vyas, microwave abosrbtion and relaxtion studies of binary mixtures of fluoro substituted anilines with some primary alcohols in benzene solutions, Indian. J. Pure andAppl. Phys.2006;44:620-624

25.   Madhurima V, Satyan N, Murthy VRK,Sobhanadri J. Dielectric studies of hydrogen bonded binary systems: ketone+nitrile Indian Journal of Pure and Applied Physics.1998; 36:144-148

26.   Thenappan T, Subramanian M. Dielectric studies of hydrogen bonded complexes of alcohols with nitriles Materials Science and Engineering B.2001; 86 :7-10

 

 

 

Accepted on 24.10.2017        © RJPT All right reserved

Research J. Pharm. and Tech 2018; 11(2):761-765.