Study of Solvent effect of Protic solvent on Solvolysis of Hexanoate ester and Activation parameters

A. K. Singh¹, L. K. Tiwari²

¹Department of Chemistry, Teerthanker Mahaveer University, Moradabad, India

²Dpartment of Mathematics, Teerthanker Mahaveer University, Moradabad, India

*Corresponding Author E-mail: anilkumar2_singh@yahoo.com

ABSTRACT:

The kinetics of alkaline hydrolysis of propyl Hexanote has been studied as a base catalyst under second order reaction at the temperature range from 20 to 40°C.The reaction rate was measured volumetrically over a range of water-propanol mixed solvent(30-70% v/v).The reaction rate was found to be increased with increasing temperature at all composition of reaction mixture. Thermodynamic parameter was calculated. The non-linear increase in free energy with mole% suggests the specific salvation taking place in reaction media. The value of iso-kinetic temperature is more than 300 which indicates strong solvent-solute interaction in reaction media.

KEYWORDS: Propyl formate, kinetics, propanol, water, solvent effect.

1. INTRODUCTION:

The report of this project is based on kinetic investigation of hydrolysis of propyl hexanoate in water- propanol media. propyl hexanoate is common ester which are used in alcoholic beverage. It is also used as solvent for polar organic compound.

Solvent effect is a rationalized term which represents the solvent polarity. It also includes the solvent solute interaction and dielectric behavior of different solvent. In mixed solvent system the solvent variation affects kinetic and electron transfer processes in complex manner in accordance with physic-chemical properties of solvent in reaction media. There is number of solvent polarity parameters like relative permittivity, solvent ionizing power etc are established to quantified, to study the influence of solvent on reactivity of initial as well as transition state.

The objective of this project to make investigation how thermodynamic parameter of aqueous solvent system reflect the kinetics parameter on base catalised hydrolysis of hexanoate ester in water-propanol media. Many reports [1-6] were published in earlier kinetics, some succeeded and some failed too.

2. EXPERIMENTAL:

The rate of hydrolysis of propyl hexanoate got observed volumetrically at five equidistance temperature over temperature range of 20°C to 40°C having extraordinary attention of solvent in response mixture of water-propanol media. Pure propyl hexanoate (Merck) become used for kinetic. Double distilled water is used through and the experiment The strength of answer retaining 0.1M with recognize to answer NaOH and 0.05M with respect to ester. The detail of manner is mention in my preceding communiqué [7] the rate steady is calculated with help of 2nd order kinetic and tabled in Table-1. With assist of Wynne-Jones and Eyring equation [8] the values of various activation parameters had been calculated and inserted in Table-2

3. RESULT AND DISCUSSION:

3.1 Effect of solvent on hydrolysis rate:

The rate constant of hydrolysis of propyl hexanoate in water-propanol solvent system was calculated using second order reaction and its value is inserted in Table-1. It is evident from this Table that specific rate constant decreases with increasing temperature from 20°C to 40°C. The factor responsible for increasing rate with temperature is due to dielectric effect and partly due to salvation in the reaction media. This outcome is good agreement with Hughes and Ingold [9] and recent publication of Bano Arjuman and Singh AK [10]

Table – I Rate constant values as function of solvent medium composition [ k x10³(dm)3/mole/mint] propyl Hexanoate.

Temp in°C	% of propanol
Temp in°C	30%	40%	50%	60%	70%
20°C	61.65	53.70	46.23	38.90	34.27
25°C	97.72	83.17	70.79	61.65	53.08
30°C	142.88	123.02	107.15	92.25	80.35
35°C	218.27	181.97	158.48	137.72	120.22
40°C	316.22	257.03	234.42	204.17	179.88

3.2 Calculated values of Iso-composition Activation Energy (E_c):

The Iso-composition Activation Energy of the reaction mixture is increases from 66.00 to 63.27KJ/Mole with increasing composition of solvent indicate desolvation and solvation in transition state and in initial state which support the recent communication of Singh A K [11]

3.3 Calculated values of Iso- Dielectric Activation Energy (E_D):

With help of Arrhenius plot the Iso- Dielectric Activation Energy (E_D) was calculated which shows decreasing trend66.00 to 58.00 KJ/mole with increasing D of reaction mixture. This is also supported by past view of Wolford [12] and recently by Singh AK.et al. [13]

3.4 Rate and thermodynamic activation Parameters of reaction:

Activation parameter, plays an important role in ester hydrolysis. The enthalpy of activation (ΔH^*) free energy of activation (ΔG^*) and entropy of activation(ΔS*) is determined using Wynne-jones and Eyring equation. [14], and the result is inserted in Table-2 with increasing mole% of solvent. Although, the variation of (ΔG^*) with mole % is negligible in comparison with the enthalpy of activation (ΔH^*) and entropy of activation (ΔS*) with increasing composition of reaction mixture but it cannot ignore. The enthalpy of activation (ΔH^*) increases with increasing mole fraction of reaction mixture (ΔS*) become more negative which indicates that there is polar transition state is preferentially solvated by water molecule. The plots of (ΔG^*) against mole % of propanol shown in fig-1 at 25°C is found to be increasing non-linearly with increasing concentration of of propanol is indicative of desolvation of reactants as explained by Elsemongy et al. [15] Significantly large change in (ΔH^*) and (ΔS*) with negligible change in (ΔG^*) with varying solvent composition can normally be attributed enthalpy domination and entropy control. This is also supported by recent communication of Singh AK [16].

Fig (1)- Variation of ∆G^* with mole % at 25°C (water-propanol)

Fig (2)- Variation of ∆H^* with mole % at 25°C (water-propanol)

Fig (3)- Variation of ∆Swith mole % at 25°C (water-propanol)

Table-2 Calculated Values Activation Parameters of the Reaction in Water-n-propanol Media [∆H^*and ∆G^*in KJ/Mole, ∆S^*in J/K/Mole.]

% of propanol	Mole %	*∆H^ in Kj/Mole**	20⁰C		25⁰C		30⁰C		35⁰C		40⁰C
% of propanol	Mole %	*∆H^ in Kj/Mole**	∆G^*	-∆S^*	∆G^*	-∆S^*	∆G^*	-∆S^*	∆G^*	-∆S^*	∆G^*	-∆S^*
30%	9.33	51.00	88.74	127.09	89.17	128.08	89.76	127.92	90.98	129.74	90.719	126.36
40%	13.79	54.81	89.68	118.89	89.57	116.64	90.08	116.40	90.66	116.39	91.13	116.03
50%	19.35	55.59	89.45	115.56	89.92	115.20	90.43	114.98	91.01	115.00	91.37	114.31
60%	26.47	57.49	89.87	110.51	90.32	110.16	90.81	109.96	91.37	110.00	91.61	109.00
70%	35.90	57.96	89.87	108.90	90.61	109.83	81.16	76.56	91.72	109.61	92.06	108.94

3.5 Iso-kinetic Temperature Solvent-Solute Interaction:

The Iso kinetic temperature is which is calculated by plotting ΔH^* against ΔS^* [fig-4] straight line slope values are found to be more than 300(365) conclude that the there is strong solvent solute interaction in reaction media. The above conclusion is also supported by Lefler [17], previously supported by Singh AK [18].

Fig. 4: Variation of ∆H* with ∆S* at 25°C (water-propanol) system

4. CONCLUSION:

By comparing the result of above project hydrolysis of propyl hexanoate in water-propanol media, following conclusion are found as:

The specific rate constant decreases with increasing solvent composition. The values of Iso-composition activation energy (E_D) increases with increasing mole% of reaction mixture. The enthalpy of activation (ΔH^*) increases with increasing mole fraction of reaction mixture (ΔS*) become more negative which indicate enthalpy entropy compensation effect in reaction media. Greater the values of iso kinetic temperature are more than 300 shows strong interaction between solute and solvent in reaction mixture.

5. REFERENCE:

1. Singh A K. Arjuman Bano, “Kinetics and Solvent effect on Aquo-dipolar protic organic-solvent system of Hexanoate ester.” Asian journal of Research in Chemistry, 12(6) Nov 2019, pp 341-344

2. Sharma Sangita et al. Kinetic study of specific base catalysed hydrolysis of Ethyl Acrylate in water-Ethanol binary system. Russian Journal of Physical Chemistry A. Vol. 87, No. 5, 2013. Pp730-736

3. Singh A K., Kinetics and solvent effect on activation parameter of aquo-propanol solvent system for acid catalyzed solvolysis of propyl formate. International Journal of Chemical Science, vol-3, issue-4, July, 2019 pp85-88

4. Singh A K., Solvent effect and kinetics on solvolysis of propyl formate in water-propanol solvent mixture. International Journal of Chemical Science, Vol-3, Issue-4, July, 2019 pp82-84

5. Magda F Fathalla., Kinetics of reaction of 2-chloro-quinosalin with Hydroxide ion in CAN- H₂O and DMSO- H₂O binary solvent mixture,” Journal of Solution Chemistry, 40, 1258-70, 2011

6. Singh AK. Arjuman Bano., Solvent effect and kinetics on ethyl benzoate in aqueous solvent system. International Journal of Chemical Science, Volume 3; Issue 5; September 2019; Page No. 26-28

7. Singh A K., Kinetics and solvent effect on activation parameter of aquo-propanol solvent system for acid catalyzed solvolysis of propyl formate. International Journal of Chemical Science ISSN:2523-2843, Vol-3, Issue-4, July, 2019 pp85-88

8. Wynne-Jones W. F. K, and Eyring, H: “The Absolute Rate of Reaction in condense Phase”. J. Chem. Phys. 3, 492-502, 1935.

9. Hughes E.D. and Ingold C.K, “Mechanism of substitution at saturated carbon atom part IV, A discussion of constitution and solvent effect on mechanism, kinetics, velocity, and orientation of substitution”. J Chem. Soc 1935, 244- 255

10. Bano Arjuman and Singh A K., “A Kinetic study of dipolar protic solvent in alkaline hydrolysis of ethyl nicotinate in water-ethanol media-A Solvent effect, “Journal of Ultra-Chemistry, Volume-13(6) Nov,2017, pp-145-150.

11. Singh A. K., Influence of solvent on solvolysis of ethyl cinnamate in water-acetone mixed solvent system. Chemical Sciences Journal 2017ISSN 2150-3494: 1, 10.4172/2150- Volume 8. Issue 1.1000150.

12. Wolford R K: “Kinetics of acid catalised hydrolysis of Acetal in dimethylsulfoxide-water solvent system at 15,25 and 35°C.” Phys Chem, 68, 3392 1964

13. Singh AK et al. Kinetics and Solvent effect on Aquo-dipolar protic organic-solvent system of Hexanoate ester.” Asian Journal of Research in Chemistry, 12(6) Nov 2019, pp 341-344

14. Wynne-jones W F K and Eyring H., The Absolute rate of reaction in condense phases” Journal of Chemical Physics 3; 492-502.

15. Elsemogy, M.M., Abu Elamayem, M.S., and Mussa, M.N.H: Z. Physik chem (Neuetold) 94, 69, 1975

16. Singh AK. Arjuman Bano., Solvent effect and kinetics on ethyl benzoate in aqueous solvent system. International Journal of Chemical Science, ISSN:2523-2843, Volume 3; Issue 5; September 2019; Page No. 26-28

17. Lefler J.E. “Entropy relationship and implication for organic chemistry.” J. Org. Chem., 20, 1201, 1955

18. Singh AK. Arjuman Bano., Solvent effect and kinetics on ethyl benzoate in aqueous solvent system. International Journal of Chemical Science, ISSN:2523-2843, Volume 3; Issue 5; September 2019; Page No. 26-28

Received on 25.02.2020 Modified on 08.03.2020

Asian J. Research Chem. 2020; 13(3):216-218.

DOI: 10.5958/0974-4150.2020.00041.3