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

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.

Full text

Asian J. Research Chem. 13(3): May-June 2020
216
ISSN 0974-4169(Print) www.ajrconline.org
0974-4150(Online)
RESEARCH ARTICLE
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.
Received on 25.02.2020 Modified on 08.03.2020
Accepted on 21.03.2020 ©AJRC All right reserved
Asian J. Research Chem. 2020; 13(3):216-218.
DOI: 10.5958/0974-4150.2020.00041.3
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

Asian J. Research Chem. 13(3): May-June 2020
217
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
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 (Ec):
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 (ED):
With help of Arrhenius plot the Iso- Dielectric
Activation Energy (ED) 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 ∆S with mole % at 25°C (water-propanol)
ΔS

Asian J. Research Chem. 13(3): May-June 2020
218
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
∆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 (ED) 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