A Study on Densities and Ultrasound Velocities in the (γ-Butyrolactone + Aliphatic Ester) System at Temperatures (303.15 To 313.15) K

A Study on Densities and Ultrasound Velocities in the (γ-Butyrolactone + Aliphatic Ester) System at Temperatures (303.15 To 313.15) K

Amara Jyothi Koppulaa Murali Krishna Patwarib Sathyanarayana Boodidac Satyanarayana Nallanid

aDepartment of Chemistry, Kakatiya University, Warangal, India.

bDepartment of Chemistry, Chaitanya Bharathi Institute of Technology, Hyderabad, India.

cDepartment of Chemistry, JNTUHCE, Karimnagar, India.

dNational Institute of Pharmaceutical Education and Research, Hyderabad, India.

Densities (), and ultrasonic velocities (u), were measured for the binary systems of -butyrolactone (GBL) with methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA) and butyl acetate (BA) at 303.15, 308.15, and 313.15 K, over the entire composition range. From the experimental results, excess molar volume (VE), and deviation in isentropic compressibility (s), were calculated. The computed properties have been fitted to a Redlich-Kister type polynomial equation to derive binary coefficients and standard deviations.

Keywords: -butyrolactone, aliphatic nitriles, excess molar volume, deviation in isentropic compressibility.

1. Introduction

   A survey of the literature showed that density, viscosity and speed of sound properties of binary mixtures of ethanenitrile and propanenitrile with MA, EA, BA,1 densities, viscosities, and refractive indices of MA, EA, and PA with 4-chorotoluene,2 densities and viscosities of MA, EA, PA, and BA with nitromethane,3 densities

   and viscosities of MA, EA, PA, ethyl propionate, and BA with nitroethane,4 density, viscosity, and speed of sound in binary mixtures of 2-chloroethanol with MA, EA, PA, BA,5 densities, and speeds of sound properties in binary mixtures of acrylonitrile with ethanenitrile, MA, EA, BA, dimethylformamide, dimethylacetamide, and dimethyl sulfoxide.6 Earlier we have reported densities, viscosities, and speeds of sound of binary mixtures of sulfolane with EA, PA, and BA.7 As a continuation of previous work in our laboratory,7 we here report excess volumes VE, and deviation in isentropic compressibility s, for four binary systems, (-butyrolactone + methyl acetate), (-butyrolactone + ethyl acetate), (-butyrolactone + propyl acetate), and (-butyrolactone + butyl acetate) at atmospheric pressure and at the temperature of 303.15, 308.15, and

   313.15 K. The experimental values of physical

   properties were used to calculate excess molar volumes, and isentropic compressibility deviations on mixing over the entire mole fraction range for the binary mixtures. The binary contribution calculated from the Redlich-Kister8 type polynomial equation, and the adjustable parameters along with the standard deviations between experimental and calculated values are shown.

   No experimental data corresponding to density, and speed of sound, have been found in the literature on the binary mixtures studied in this paper.

   1. Materials

2. Experimental

   The excess molar volumes (VE) have been evaluated from density using

   All the component liquids are of analytical grade and are procured from Sigma-Aldrich, U.S.

   -Butyrolactone was purified by being distilled twice under reduced pressure.9 Prior to measurements, all the chemicals with stated purities of better than 90 % were kept on molecular sieves (0.3 nm Merck, India) to remove any trace of water and degassed just before use. The densities and speed of sound of pure substances and their comparison with literature values are listed in Table 1.10-12

   1. Apparatus and procedure

   Binary mixtures were prepared by mass in air tight bottles. The mass measurements were performed on a Dhona 100 DS, India, single pan analytical balance with a resolution of ± 0.01.10-6 kg. The required properties of the mixture were measured on the same day. The uncertainty in mole fraction was estimated to be less than ± 1.10-4. Density of pure liquids and their mixtures were determined by using a 1.10-5 m3 double arm pycnometer.13 The uncertainties in density and excess molar volume values was found to be ± 4.10-5 g.cm-3 and 1.10-3 cm3 .mol-1.

   Speeds of sound were determined by using an ultrasonic interferometer (Model M-82, Mittal Enterprises, India) operating at a 2 MHz frequency. The working principle used in the measurement of the speed of sound through a medium was based on the accurate determination of the wavelength of ultrasonic waves of known frequency produced by a quartz crystal in the measuring cell.14,15 The temperature of the solution was controlled by circulating water at a desired temperature through the jacket of the double-walled cell. The speed of sound was measured with relative uncertainty of 0.3%.

   In all the property measurements the temperature was controlled within ± 0.01 K using a constant temperature bath (INSREF model IRI-016 C, India), and the temperature was monitored with a platinum resistance thermometer with an accuracy of ± 0.001 K and an uncertainty of ± 0.004 K.

3. Results and discussion

   Experimental values of density () and speed of sound

   (u) for the binary mixtures of -butyrolactone with methyl acetate, ethyl acetate, propyl acetate, and butyl acetate at T = (303.15, 308.15 and 313.15) K as a function of mole fraction are listed in Table 2.

   VE = (x1M1+ x2M2)/m (x1M1/1+ x2M2/2) (1)

   where m is the density of the mixture; x1, M1, 1 and x2, M2 and 2 are the mole fraction, molar mass and density of pure components respectively.

   The deviations in isentropic compressibility (s) have been evaluated using the equation

   s = s(1s1+2s2) (2)

   wheres1, s2 and s are the isentropic compressibility of the pure components and observed isentropic compressibility of liquid mixture respectively.

   i is the volume fraction and is calculated from the individual pure molar volumes, Vi, using the relation

   I = xiVi/(xiVi) (3)

   The excess or deviation properties Y were fitted by the method of non linear least squares to a Redlich- Kister type polynomial equation8

   Y = x1x2 Ai (x1-x2)i (4)

   where A0, A1, A2, A3, and A4 are adjustable binary coefficients. The coefficients Ai were estimated using multiparametric regression analysis based on a nonlinear least-squares method. The number of Ai parameters was optimized using F-test and is found to be (m = 5). In each case, the optimum number of coefficients Ai is determined from an examination of the variation of standard deviation () as calculated by

   (Y) = [ (Y obs – Y cal) 2/ (n m)] ½

   (5)

   where n represents the number of experimental points and m is the number of coefficients used in fitting the data. The coefficients Ai and the estimated standard deviations ()VE and ()s of the fit are shown in Table 3.

   1. Excess Molar Volume (VE).

      Dependences of excess molar volumes (VE) for the mixtures investigated on the mole fraction of component 1, (x1) at T = 303.15, 308.15 and 313.15 K

      are depicted graphically in figures 1, 2, 3, & 4. It can be seen that values of excess molar volume (VE) are all negative for the four binary mixtures over the entire composition range, indicating negative deviations from ideal behaviors. The largest deviations are all located at x1 0.5-0.6. The negative VE values for aliphatic esters at 303.15 K fall in the sequence:

      BA < MA < EA < PA < 0

      The above observation seen at all the temperatures (i.e.,

      308.15 and 313.15 K) and are more negative with increasingchain length of the ester molecules except in the case of BA.

      The negative VE values suggest specific interactions acting between the mixing components. The interactions may be classified as dipole-dipole forces resulting from the polarizability of ester molecules by the dipoles of -butyrolactone molecules (because of its large dipole moment µ = 4.12D).

      The effect of temperature on VE is noteworthy. There is a gradual decrease, followed by an increase in VE with a rise in temperature for all mixtures except for EA, as shown in Fig. 4. Also the curves do not show

      any systematic variation with the size of the esters.

      Figure 1. Plots of excess molar volumes, VE, as a function of mole fraction x at T = 303.15 K; , {GBL (1) + MA (2)}; ; {GBL (1) + EA (2)}; , {GBL (1) +

      PA (2)}; , {GBL (1) + BA (2)}; the symbols represent experimental values and lines represent the smoothed data of this work.

      The negative deviations at all the temperatures and at equimolar composition follow the same trend but show different values except for EA and PA at 308.15 K which interchanges.

      Figure 2. Plots of excess molar volumes, VE, as a function of mole fraction x at T = 308.15 K; , {GBL (1) + MA (2)}; ; {GBL (1) + EA (2)}; , {GBL (1) +

      PA (2)}; , {GBL (1) + BA (2)}; the symbols represent

      experimental values and lines represent the smoothed data of this work.

      Figure 3. Plots of excess molar volumes, VE, as a function of mole fraction x at T = 313.15 K; , {GBL (1)

      + MA (2)}; ; {GBL (1) + EA (2)}; , {GBL (1) + PA (2)};

      , {GBL (1) + BA (2)}; the symbols represent experimental values and lines represent the smoothed data of this work.

   2. Deviation in Isentropic Compressibility (s).

   The variation of s with volume fraction, 1, of – butyrolactone with esters is presented in Table 2. All the systems of GBL + esters show negative deviations through s isotherms over the entire range of volume fractions and become more negative at higher temperatures. The negative s values for aliphatic esters at 313.15 K fall in the sequence:

   PA < BA < EA < MA < 0

   From the above observation s values become more negative with increasing chain length of the ester except for PA at 313.15 K. The s vs 1 curve at

   1. and 313.15 K show the same trends, but these are not shown to avoid overcrowding. However, the effect of temperature on s values is significant.

      In general the dependence of VE and s on composition is unsymmetrical and the magnitude varies with the type of solvent used.

4. Conclusion

In this paper we present the new experimental values on density and speeds of sound are measured between T = 303.15, 308.15 and 313.15 K and at

different compositions for four binary liquid mixtures of (-butyrolactone +methyl acetate), (- butyrolactone +ethyl acetate), (-butyrolactone

+propyl acetate), and (-butyrolactone +butyl acetate). We have calculated the excess molar volume (VE) and deviation in isentropic compressibility (s) using the Redlich-Kister type equation. Excess molar volume and deviation in isentropic compressibility are negative. The sign of these quantities have been discussed in terms of the dipole-dipole interactions.

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-Butyrolactone (1) + Butyl Acetate (2) T = 303.15 K