Solvent Effect on the Enthalpy and Entropy of Activation for the Hydrolysis of Ethyl Cinnamate in Mixed Solvent System

(IJEACS) International Journal of Engineering and Applied Computer Science
Volume: 02, Issue: 04, April 2017
ISBN: 978-0-9957075-5-9
www.ijeacs.com
DOI: 10.24032/ijeacs/0204/01
123
Solvent Effect on the Enthalpy and Entropy of
Activation for the Hydrolysis of Ethyl Cinnamate in
Mixed Solvent System
A. K. Singh
Department of Chemistry
Teerthanker Mahaveer University, Moradabad, India
Abstract— The rate of alkaline hydrolysis of ethyl cinnamate was
measured over the temperature range of 20o
C to 40 o
C in water-
acetone mixture at different composition 30 to 70% (v/v). The
influence of solvent variation on reaction rate was examined in
term of changes in the activation parameter. Depletion of H*
and S*
value with simultaneous increase in G*
of the reaction
in reaction media, reveals that the reaction is Enthalpy
domination and Entropy controlled. The Iso- dielectric activation
energy(ED) of reaction was found to decrease from 52.43 to 47.28
which is calculated by plotting log k values against different D.
The Values of Iso-kinetic Temperature which is less than 300,
clearly indicates that there is no appreciable interaction between
solvent and solute present in the reaction media, i.e. reaction is
not ion-dipole but ion-molecule type.
Keywords- Activation Parameter; solvent-solute interaction;
Iso-kinetic temperature; specific salvation; Iso Dielectric Activation
Energy.
I. INTRODUCTION
Solvent play an important role in determining chemical
reactivity. In particular, the rate of an elementary chemical
reaction may change by orders of magnitude when solvent is
changed. Kinetic solvent effect on chemical reaction in
different media is correlated in terms of “solvent polarity”
which is sums of all the specific and non-specific interaction
of the media with initial and transition state”. A large effort
has been directed towards understanding such solvent effect
and a great deal of progress has been made recently [1-3] both
theoretically and experimentally. However, the interpretation
of kinetic result on the solvent polarity on medium some time
fails and sometime succeeds.
In this note we have extended our studies on kinetic solvent
on well-known base catalyzed hydrolysis of Ethyl cinnamete
which is important for use of adding to cigarettes and cut
tobacco that are used for flavor agent and fragrance agent.
II. EXPERIMENT
The kinetics of base catalyzed hydrolysis of ethyl
cinnamate has been carried out volumetric in water-acetone
medium having different concentration of solvent (acetone),
varying from 30 to 70% (v/v) at five different temperature
ranging from 20o
C to 40 o
C at regular interval of 5o
C. The
specific rate constant calculated using second order reaction
was found decrease with increase of acetone content, The iso
dielectric Activation energy(ED) is also calculated with help of
slope of logkD against 103
/T(Tab-I) at constant D and
tabulated in Table-II. The iso kinetic temperature was
calculated with help of Barclay and Butler relation which
come less than300.
The evaluated thermodynamic activation parameter has
been tabulated in Table-III.
III. RESULT AND DISCUSSION
A. Solvent Effect on Rate of Reaction
In order to discuss the variation of specific rate constant
values with gradual addition of dipolar aprotic organic solvent
(acetone) in reaction media, the value logk is calculated using
second order kinetic. The decrease observed in specific rate
constant, with increasing concentration of organic solvent is
probably due to depletion of Dielectric constant of media or
decreasing polarity of medium as changing from polar water
to less polar water-acetone medium. Singh A K [4].
B. Solvent Effect on the Iso- Dielectric Activation Energy of
Activation
From the slope of Arrhenius plot (obtain from interpolation
of logkD value against 103
/T at constant D (Tab-I) of reaction
media. The value of Iso dielectric activation energy of reaction
have been evaluated and represented in Tab-II. ( Fig.1 ). It is
obvious that ED value goes on decreasing from 52.43 to47.28
KJ/mole with increasing in D value of water –Acetone media,
is similar trend to recent finding of Singh R T et al. [5].

A. K. Singh (IJEACS) International Journal of Engineering and Applied Computer Science
ISBN: 978-0-9957075-5-9
www.ijeacs.com
DOI: 10.24032/ijeacs/0204/01
124
Table - I
3 + LogkD Value against 103
/T, Water- Acetone System
Table - II
Values of Iso-Dielectric Activation Energy (water-Acetone media)
Figure 1. Variation of 3+LogkD with 103
/T
C. Solvent Effect and Thermodynamic activation parameters
The thermodynamics Activation parameter such as Enthalpy
of Activation (H*
), Entropy of Activation (S*
) and free
energy of Activation (G*
), are better indicator of the solvent
effect exerted by the solvent on the solvolysis reaction. These
thermodynamics Activation parameter has been calculated
with help of Wyne-Jones Eyring[6] equation and absolute rate
theory[7] and placed in Tab-III.
On careful observation of the data Tabulated in table III
(water-acetone) G*
value in case of water-acetone increases
from 92.09 to 94.26 KJ/mole with change of proportion of
solvents from 20% to 70% at 20o
C. Though the enhancement
is not large, however it is quite considerable.
The report of Yagil and Anbar[8] indicate that OHˉ ion of
NaOH is hydrated with three molecules of water. In mixed
aquo-organic co-solvent mixture, the organic component
molecules are expected to contribute to the process of
desolvation as they may be regarded as poor anion solvater in
comparison to water. A similar variation in G*
values with
increasing mole % of organic co solvent has been reported by
Tommila [9] and Cleave [10] and recently Singh A K[11]
The variation of G*
with mole% in the solvent are
nonlinear and increase smoothly with gradual addition of the
solvent (Fig. 2 ). This finding is indicative of salvation or
desolation of reactant as explained by Absolute Reaction rate
theoryand supported by Elsemongy [12] and Singh A K. [13]
From data mention in the table III, the interesting feature
comes in the light is that out of all the value of three
thermodynamic parameter H*
, G*
, and S*
, the value of
H*
and S*
goes on decreasing with simultaneous increase in
G*
values with increasing proportion of acetone at all the
temperature of the reaction, i.e. from 20o
C to 400
C. From the
fundamental thermodynamic equation
G*
= H*
– TS*
it may be inferred that the enhancement in the value of G*
with simultaneous depletion in H*
and S*
value is only
possible when the quantitative depletion in the value of S*
is
less than that found in the values of H*
and from this fact, it
is concluded that base catalyzed hydrolysis of Ethyl
Cinnamate in water-acetone media is Enthalpy dominating and
Entropy controlled. In another word, it may also be inferred
that in presence of acetone in the reaction media activate the
Enthalpy and control over the Entropy of the reaction.
The change found in the value of three thermodynamic
Activation parameter also support the fact that initial state of
the reaction is desolvated and the transition state is solvated in
the similar ways as recently reported by Singh A K, [14]
To explain the solvent effect on the thermodynamic
parameters these three values namely G*
, H*
and S*
were
plotted against mole% of acetone in reaction shown in Fig- 2
3and 4 respectively. The nonlinear variation in H*
and S*
give information specific salvation taking place in water-
acetone as reported by Saviil et al. [15]

ISBN: 978-0-9957075-5-9
www.ijeacs.com
DOI: 10.24032/ijeacs/0204/01
125
Table-III
Thermodynamics Activation Parameters of the Reaction in Water- Acetone
Media ( ∆H*
and ∆G*
in KJ/Mole, ∆S*
in J/K/Mole)
Figure 2. Variation of G* with mole %
Figure 3. Variation of * with mole %
Figure 4. Variation of S*+200 with mole%
D. Evaluation of Iso-kinetic Temperature and Solvent-Solute
Interaction
In the light of Barclay and Butler [15] relationship between
Enthalpy and Entropy of Activation, which is as follows
δm (H*
) = βδm(S*
)
It is straight line equation representing the relationship
between Enthalpy and Entropy of Activation. β is the Iso-
kinetic temperature.
From the data available in the table IV the plot of H*
and
S*
in the solvent system in Fig. 5 and from the slope of
straight line, the value of Iso-kinetic temperature was
calculated to be 244 (water-acetone) and which is less than
300.
From the value of Iso-kinetic temperature which is much
less than 300, it is concluded that there is slow change in the
structure of the reactant or in the solvent or in due to weak
interaction between solvent and solute present in the reaction
media in similar way as reported by Lefler[16] Our this
conclusion has been recently supported by Singh A. K.[18].
Figure 5. Variation of * with S*+200 at 30o
C
IV. CONCLUSION
The result of this work indicate that the rate of hydrolysis of
Ethyl cinnamate decreasing trend at all temp witch appear that
transition state is more desolveted than initial state. The
enhancement in the value of and G*
with simultaneous
depletion in H*
∆S*
for the hydrolysis ethyl inanimate in
water- acetone is enthalpy dominating and Enthalpy control.
The linear plots obtained by plotting logk as function of D
represent the different electrostatic interaction for the ion-
dipole as well as dipole - dipole reaction. The much less value
(>300) of iso kinetic temps indicate weak interaction between
solvent and solute.
ACKNOWLEDGMENT
My special gratitude to my supervisor Prof. R T Singh for
his proper guidance and thanks to my friend Dr. Ajit, Dr.
Parag and Mr. L K Tiwari for his cooperation during
preparation of this content. I am Thankful to Mrs. Rolly Gupta
& Mss. Akansha for their assistance.

ISBN: 978-0-9957075-5-9
www.ijeacs.com
DOI: 10.24032/ijeacs/0204/01
126
REFERENCES
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bond cleavage in p. chloro and p. bromo oxazolinanes in Acetone nitrile-
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[3] Magda F. Fathalla, Kinetics of reaction of 2-chloro-quinosalin with
hydroxide ion in CAN-H2O and DMSO- H2O binary solvent mixture”
j. Solution Chem., 40, 1258-70, 2011
[4] Singh A K. “The influence of solvent on solvolysis of ethyl cinnamate in
water- acetone mixed solvent system.” International journal of
engineering and applied computer science[IJEACS]. Vol-02, Issue 02,
Feb 2017 pp79-82
[5] Singh R T et al. “Kinetic study on the dielectric effect of water-t-butanol
media on solvolysis of caproate ester.” Napier Indian Advance Research
Journal of Science, vol-12 sep 2013, pp78-88
[6] Wynne-Jones W. F. K,and Eyring, H,: “ The Absolute Rate of Reaction
in condense Phase”. J. chem.. phys. 3, 492-502, 1935.
[7] Glasston, S, Laidler K J and Eyring, H,: The theory of rate process. Mc
Graw-Hill Newyork (1941)
[8] Yagil, G. and Anbar N. J., “ Classics in solid phase synthesis.” J Am.
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[9] Tommila. E., Influnce of solvent on reaction velocity. Acta. Chem.
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[10] Cleave, N J ., Soumen Kemi 45B 1935 pp 79-80.
[11] Singh A K. “ A kinetic study of solvent effect on thermodynamic
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innovation. Vol-3, issue-3 2015 pp-547-549
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[14] Singh A K. “A Kinetics Studies of Solvent Effect on Thermodynamic
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AUTHOR PROFILE
Dr. A. K. Singh is working as Asst. Professor of
Chemistry in College of Engineering of Teethankar
Mahaveer University, Moradabad, India since
2010. He holds Master of Science in Physical
Chemistry, awarded in 1989, from Magadh
University, Gaya followed by Doctor of
Philosophy (Ph.D.) in Kinetic Solvent Effect,
awarded in 2009 from VKS University Ara, India.
He has studied different salvation capacity of
different reaction media (e.g. Water-DMSO, Water-DMF,Water-Aceton.
Water-Methanol etc) on the Specific Rate Constant value of the Reaction, the
Iso- Composition, Iso- Dielectric Activation Energy, the Number of Water
and Solvent Molecules Associated the Activated complex of the Reaction in
order to decide the Nature of Mechanistic path of the Reaction,
Thermodynamic Activation Parameter of the Reaction, the value of Iso
Kinetic Temp on the Reaction in order to Explore the Idea of Solvent- Solute
Interaction in More Media. He has published seventeen research articles in his
credits.
© 2017 by the author(s); licensee Empirical Research Press Ltd. United Kingdom. This is an open access article
distributed under the terms and conditions of the Creative Commons by Attribution (CC-BY) license.
(http://creativecommons.org/licenses/by/4.0/).

Solvent Effect on the Enthalpy and Entropy of Activation for the Hydrolysis of Ethyl Cinnamate in Mixed Solvent System

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