Kinetic investigation of oxidation of aromatic anils by potassium peroxymonosulfate in aqueous acidic medium

Article abstract of DOI:10.1002/kin.20794

The kinetics of oxidation of aromatic anils to benzaldehyde and azobenzene by potassium peroxymonosulfate has been studied in aqueous acetic acid medium. The low dielectric constant of the medium facilitates the reactivity. It has been found that the variation in the ionic strength of the reaction has a negligible effect on the rate. Similarly, polymerization was not observed when acrylonitrile was added to the reaction mixture. This observation rules out the formation of any free radical in the reaction. The added Mn(II) increases the rate of the reaction, which indicates the involvement of two-electron transfer. Highly negative ΔS^# values indicate a structured transition state. The deviation of the Hammett plot was noted, and a concave downward curve was obtained for the anils with substituents in the aniline moiety. The observed break in the log k_obs versus σ is attributed to the transition state whereas the concave upward curve was observed for the substituents in the benzaldehyde moiety and in the combination of aniline and benzaldehyde moieties, and a suitable mechanism was proposed.

Full text of DOI:10.1002/kin.20794

Kinetic Investigation of
Oxidation of Aromatic
Anils by Potassium
Peroxymonosulfate in
Aqueous Acidic Medium
R. VENKATESH, K. KARUNAKARAN
Department of Chemistry, Sona College of Technology (Autonomous), Salem 636 005, India
Received 13 September 2012; revised 8 January 2013; accepted 27 February 2013
DOI 10.1002/kin.20794
Published online 21 June 2013 in Wiley Online Library (wileyonlinelibrary.com).
ABSTRACT: The kinetics of oxidation of aromatic anils to benzaldehyde and azobenzene by
potassium peroxymonosulfate has been studied in aqueous acetic acid medium. The low
dielectric constant of the medium facilitates the reactivity. It has been found that the variation
in the ionic strength of the reaction has a negligible effect on the rate. Similarly, polymerization
was not observed when acrylonitrile was added to the reaction mixture. This observation rules
out the formation of any free radical in the reaction. The added Mn(II) increases the rate of
the reaction, which indicates the involvement of two-electron transfer. Highly negative ꢀS#
values indicate a structured transition state. The deviation of the Hammett plot was noted,
and a concave downward curve was obtained for the anils with substituents in the aniline
moiety. The observed break in the log kobs versus σ is attributed to the transition state whereas
the concave upward curve was observed for the substituents in the benzaldehyde moiety and
in the combination of aniline and benzaldehyde moieties, and a suitable mechanism was
proposed. ꢀC 2013 Wiley Periodicals, Inc. Int J Chem Kinet 45: 542–550, 2013
PMS is found to be more efficient than hydrogen per-
oxide or persulfate [3]. Broad applications of potas-
sium peroxymonosulfate (PPMS), an efficient oxidant,
have been performed in organic synthesis recently due
to its versatility, stability, operation simplicity, non-
toxicity, and low costs [4]. PPMS is obtained as a
mixture of KHSO5–K2SO4–KHSO4. The triple salt,
2KHSO5–K2SO4–KHSO4, is commercially known as
Oxone, which is a monosubstituted derivative of H2O2.
Thus, it is thermodynamically more powerful as an
oxidant than H2O2 and kinetically more reactive. I−n
acid medium, the triple salt gives the active “HSO5.
INTRODUCTION
Peroxymonosulfate (PMS) is used as a powerful ox-
idant for a wide variety of industrial and consumer
applications [1]. PMS often oxidizes faster than hydro-
gen peroxide and is slightly more powerful as an oxi-
dant (EH0 SO−
= +1.82 V; EH0 O /H O = +1.76 V)
5 /HSO−4
2
2
2
[2]. When used in organic synthesis as an oxidant,
Correspondence to: K. Karunakaran; e-mail: drkk@sonatech
.ac.in.
C
ꢀ
2013 Wiley Periodicals, Inc.

KINETIC INVESTIGATION OF OXIDATION OF AROMATIC ANILS BY PPMS
543
was controlled to 0.1◦C. The reactions were per-
formed under pseudo–first-order conditions by main-
taining excess of anil over the oxidant. The mixture was
homogeneous throughout the course of the reaction.
The progress of the reactions was followed by esti-
mating the unreacted oxidant iodometrically at regular
time intervals. The rate constants (kobs) were obtained
from log (titer) versus time plots. All the rate constants
were averages of two or more determinations. Under
kinetic conditions, stoichiometric amounts of the sub-
strate and PPMS were mixed. After 24 h, the acetic
acid was neutralized and the reaction mixture ethanol
was extracted. The dark brown extract, when subjected
to thin-layer chromatography, gave two distinct spots.
On evaporation of ethanol, the products were found to
be benzaldehyde, which was confirmed by the isola-
tion of its 2,4-dinitrophenylhydrazone derivative and
azobenzene identified by its melting point and a UV–
vis spectrum. The λmax of azobenzene was confirmed
by comparing with that of the authentic sample in aque-
ous acetic acid medium.
HSO5, −” a potentially important strong oxidant, which
is first described in the oxidation reactions [5,6] and
some of the later studies including the oxidations of
aldehydes [7], [(NH3)5CoS2O3]+ [8], amino acids [9],
sulfide ion [10], tris(2,2-bipyridyl)Ru(II) [11], Ti(III−),
Fe(II), and α-oxygen–substituted radicals [12], NO2
ion [13], parasubstituted anilines [14], aminobenzoic
acids [15], “Co2+” ion in the presence of molybdate
ion, [16], and that of [Co(II)W12O40]6− [17]. Schiff
–
= –
bases are nitrogen donor ligands ( CH N ) that form
complexes by donating an electron pair to a metal atom
in the formation of coordination compounds. Schiff
bases have found wide applications in the field of co-
ordination chemistry [18], biological processes [19],
several enzymes [20], microcalorimetry [21], cytotoxic
[22], insulin mimetic agents [23], anticonvulsant [24],
antiproliterative [25], antifungal activities [26], “trans-
port of oxygen in mammalian,” and other respiratory
–
= –
systems [27]. Aromatic anils, X CH N Y have two
phenyl rings X and Y, the ring X originates from the
aromatic benzaldehyde moiety and Y from the aniline
moiety. It is possible to evaluate the reaction constant
(ρ) from the Hammett plot by varying the substituents
in one of the rings X or Y, and keeping the same sub-
stituent in the other ring. It is therefore possible to get
several reaction constants for different substituents in
one of the two rings. The kinetics and mechanism of
oxidation of some substituted anils, using several oxi-
dants, have been reported [28–37]. A literature survey
reveals that no report is available on the kinetics of oxi-
dation of meta- and parasubstituted aromatic anils with
PPMS; hence it is worthwhile to do research on the ki-
netics and mechanism of oxidation of anils by PPMS.
The oxidation reactions of meta- and parasub-
stituents of aromatic anils were studied at different
temperatures (298, 303, 308, 313, and 318K) to eval-
uate various thermodynamic parameters. From the
Eyrings equation [39], the thermodynamic parameters,
enthalpy of activation, and entropy of activation are
calculated from the following expression:
#
kobs = (kbT /h) expꢀG /RT
where kb is Boltzmann’s constant, T is the temperature
in kelvin, h is plank’s constant, and R is the gas con-
stant. ꢀG# is the activation of Gibbs free energy, and
the energy of activation (Ea) can be calculated from the
following expressions, respectively:
EXPERIMENTAL
ꢀG# = ꢀH# − T ꢀS
Ea = ꢀH# + RT
Anils were prepared [38] by refluxing equimolar quan-
tities of benzaldehyde and aniline in ethanol for about
2–3 h. The resulting solution was cooled and poured
into cold water. The precipitated anil was filtered off,
washed with ethanol, and dried. It was recrystallized
from ethanol. The purity of the anils was checked by
determining their melting points and FT-IR spectrum
(mp 53◦C [lit. 54◦C]), microanalysis Found: C 86.10,
H 6.02, N 7.68; calculated: C 86.18, H 6.07, N 7.73. All
other chemicals used were of analytical grade (Merck,
Mumbai, India). Acetic acid was purified by redistil-
lation. All the reagents were prepared just before the
reactions were carried out. The aqueous solution of
PPMS (Sigma Aldrich, Bangalore, India) was prepared
fresh and standardized iodometrically. All the reactions
were carried out in a thermostat, and the temperature
where ꢀH# is the enthalpy of activation and ꢀS# is the
entropy of activation.
RESULTS AND DISCUSSION
The reaction followed first-order kinetics with respect
to the concentration of anil and PPMS, respectively.
Under the identical experimental conditions [Anil]
ꢁ[PPMS], the pseudo–first-order linear plot of log
(titer) versus time is linear upto 90%, depicted in
Fig. 1. The order in [Anil] was first, as revealed by
the slope of the plot of log kobs against log [Anil]
International Journal of Chemical Kinetics DOI 10.1002/kin.20794

544
VENKATESH AND KARUNAKARAN
Table I Effect of Varying the Concentration of Anil,
PPMS, H2SO4, and Solvent Composition on the Rate at
308 K
r2 = 1.996
y = a + bx
1.4
1.2
1.0
0.8
0.6
0.4
[Anil] (×
[PPMS] (×
[H+]
HOAc kobs (×
102 mol dm−3) 103 mol dm−3) (mol dm−3) (%) 104 s−1
)
6.0
7.0
8.0
9.0
10.0
11.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
5.0
5.0
5.0
5.0
5.0
5.0
3.0
4.0
5.0
6.0
7.0
8.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.8
0.9
1.0
1.1
1.2
1.0
1.0
1.0
1.0
1.0
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
30
40
50
60
70
3.66
4.57
4.93
5.81
6.50
7.25
4.88
4.79
4.93
4.86
4.91
4.72
6.22
5.68
4.93
4.42
4.09
5.65
4.83
4.57
4.35
3.91
0
200
400
600
800 1000 1200 1400 1600 1800
Time (s)
Figure 1 Pseudo–first-order plot for PPMS oxidation of
aromatic anil at 308 K.
–3.10
Slope = 1.09
r = 0.996
–3.15
–3.20
–3.25
–3.30
–3.35
–3.40
-3.45
Table II Effect of [Mn(II)], [Acrylonitrile], [Na2SO4] on
the Reaction Rate at 308 K
[Mn(II)]
(mol dm−3
[Acrylonitrile]
[Na2SO4]
(mol dm−3
kobs (×
)
(mol dm−3
)
)
104 s−1
)
–1.25
–1.20
–1.15
–1.10
–1.05
–1.00
–0.95
log [Anil]
0
0.02
0.04
0.06
0.08
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
0
0.02
0.04
0.06
0.08
4.93
5.62
6.41
7.22
7.87
4.93
5.07
5.01
4.88
4.99
4.93
5.22
5.41
5.74
5.87
Figure 2 Plot of log kobs versus log [Anil] at 308 K.
(Fig. 2), with the correlation coefficient (r = 0.996).
The kinetic order in acidity appears to be unity
but increases in [H+]; the rate of the reaction was
decreased. The kinetic results are summarized in
Table I. The ionic strength of the reaction varies by the
addition of Na2SO4, and its influence on the reaction
rate was studied and has been found that it has no
significant effect on the reactivity. No polymerization
with acrylonitrile was observed. Addition of Mn(II)
increases the rate of the reaction, and the rate data
are listed in Table II. Temperature dependence
studies were conducted for all the substituted anils
(substitution in X and Y ring separately) between
298 and 318 K. The rate constants for the reaction
systems and activation parameters were evaluated
from the Eyring plots as listed in Table III. When an
attempt was made to fit in the rate data of meta- and
parasubstituted anils (substitution in the aniline moiety
and benzaldehyde moiety separately and substitution
0
0.02
0.04
0.06
0.08
–
–
–
–
–
[Anil]
=
0.08 mol dm−3
;
[PPMS]
=
0.005 mol dm−3
;
[H2SO4] = 1.0 mol dm−3; HOAc – H2O = 50% (v/v); tempera-
ture = 308 K.
in both aniline and benzaldehyde moieties) into
the Hammett equation, a concave downward curve
was obtained for the anils with substituents in the
aniline moiety, whereas the concave upward curve
was observed for the substituents in the benzaldehyde
International Journal of Chemical Kinetics DOI 10.1002/kin.20794

KINETIC INVESTIGATION OF OXIDATION OF AROMATIC ANILS BY PPMS
545
International Journal of Chemical Kinetics DOI 10.1002/kin.20794

546
VENKATESH AND KARUNAKARAN
Table IV Pseudo–First-Order-Rate Constants for the
Oxidation of Anils by PPMS in Different Acetic Acid
Compositions
K1
2- + H+
-
SO5
HSO-5
HSO5
k2
[Complex]
C H CH=
+
NC6H5
6
5
Acetic
Dielectric
kobs (×
Slow
Acid (%)
Constant (D)
104 S−1
)
+
C6H5CHO
H SO
2 4
C6H5 NH +
[Complex]
2C6H5+NH
+
30
40
50
60
70
56.83
49.60
42.37
35.14
27.90
5.65
4.83
4.57
4.35
3.95
Dimerizes
C H N NC H
6 5
+
2H+
=
6
5
Scheme 1 Probable mechanism for the oxidation of aro-
matic anil by PPMS.
[Anil] = 0.1 mol dm−3; [PPMS] = 0.005 mol dm−3; [H2SO4] =
1.0 mol dm−3; HOAc – H2O = 50% (v/v).
The investigation results illustrate a fascinating note
that the increase in H+ retards the rate of the reaction.
With the decrease in pH, the molecule gains a proton,
becomes less negatively charged, and hence the rate of
the reaction decreases [41]:
moiety and a concacve upward curve was observed
for the substituents in the combination of aniline and
benzaldehyde moieties.
HSO−5 ꢀ SO25− + H+
Effect of the Dielectric Constant
The effect of solvent on the reaction rate was studied
by varying the composition of acetic acid from 30%
to 70% (Table IV). The oxidations were carried out by
maintaining the concentration of anils and PPMS and
temperature constant. The above observation clearly
reveals that the rate decreases with an increase in the
percentage of acetic acid, i.e., with decreasing dielec-
tric constant (D) or low dielectric constant or polarity
of the medium. This directs to the conclusion that there
is a charge development in the intermediate state in-
volving a more polar intermediate than reactants, sug-
gesting a polar (ionic) mechanism. The low dielectric
constant of the medium facilitates the reactivity.
−
2−
The species HSO5 is more reactive than SO5
−
species. The higher reactivity of HSO5 is consistent
both with an electrostatic effect and with weakening of
the peroxide bond by the proton [42]. Also, in strong
acid, the anil exists as a C6H5CH +NHC6H5 form. It
=
is observed that when the acid strength is increased,
there is a decrease in the rate, which may be due
to the less reactive protonated form than nonproto-
nated form. Based on the stoichiometry of the reaction
and above experimental results, the following reactions
(Scheme 1) are believed to constitute the most probable
mechanism of the reaction. The formation of complex
is in agreement with the literature study [43,44], and
the intermediate formed is experimentally confirmed
at 790 nm (Fig. 3). The next step (decomposition of
Mechanism
The known fact is that the free radicals can be pro-
duced by the homolytic fission of peroxide bond. An
acrylonitrile monomer is having capability to trap the
free radicals with the formation of polymer. But, in the
oxidation reaction it does not form any polymer (no for-
mation of turbidity). Furthermore, the rate of conver-
sion is invariant when acrylonitrile is added. This rules
out the presence of the free radical mechanism in this
oxidation reaction. So the ionic reaction is preferred
in this oxidation study. Commonly, the enhancement
of the electrophilic activity of peroxide will minimize
the significance of undesirable free radical methods,
resulting in a mixture of products [40]. A literature
study [40] reveals that at higher pH the PMS exists
– –
as a dianion (AO O O3A) and at lower pH, the oxidant
Figure 3 UV spectrum showing a probable formation of
an intermediate complex in oxidation of aromatic anil by
PPMS.
exists as HSO5A ions. The absorption spectra represent
spectral changes, supporting the complex formation.
International Journal of Chemical Kinetics DOI 10.1002/kin.20794

KINETIC INVESTIGATION OF OXIDATION OF AROMATIC ANILS BY PPMS
547
Table V Reaction Constant for the PPMS Oxidation of
Aromatic Anils
complex) is a slow reaction and is likely to be the rate-
determining step. Simultaneously, at 429 nm, a peak
appears and is stable until the end of the reaction, which
is the azobenzene product. Based on the above experi-
mental observations, a probable mechanism, shown in
Scheme 1, is suggested.
Substituent
Temperature (K)
ρ+
ρ−
Aniline moiety
298
303
308
313
318
298
303
308
313
318
298
303
308
313
318
1.7342
1.7227
1.6063
1.4177
1.1474
1.5861
1.4723
1.3081
1.1674
0.9896
1.6976
1.3471
1.3555
1.2899
1.1960
0.8407
0.7561
0.7002
0.6981
0.3285
0.7984
0.7632
0.7406
0.5688
0.2781
0.8273
0.7946
0.7731
0.6522
0.5975
The above mechanism leads to the following rate
law:
Benzaldehyde
moiety
Rate = − [KHSO ]/ t = K k [anil] [KHSO ]
d
d
5
1
2
5
This rate law satisfactorily explains all the experi-
mental results.
Combination of
aniline and
benzaldehyde
moieties
Effect of Substituents
The effect of substituents on the rate was studied by
varying the substituents H, m-CH3, p-CH3, p-OC2H5,
p-OCH3, p-Cl, m-Cl, m-NO2, and p-NO2 in one of
the ring benzaldehyde (or) aniline and in both at five
different temperatures 298, 303, 308, 313, and 318K
(Table III); ꢀH# and ꢀS# values were calculated from
the slope and intercept of the plot ln kobs /T versus 1/T,
respectively.
isokinetic and Exner plots reveal that there is no change
in the reaction mechanism with respect to substituents
in the aniline moiety. Para- and metasubstituted anils
with substituents in the aniline moiety in aqueous acetic
acid at 298–318 K confirm the Exner relationship, also
the activation parameters to the isokinetic relationship
but not to any of the linear free energy relationships.
The isokinetic temperature lies within the experimen-
tal range. With the knowledge of substituent constants,
it is possible to obtain reaction constants for a wide
range of organic reactions. The reaction constant, or
sensitivity constant, ρ, describes the susceptibility of
the reaction to substituents, compared to the ioniza-
tion of benzoic acid. It is equivalent to the slope of
the Hammett plot. As the value of ρ is related to the
charge during the rate-determining step, mechanisms
can be devised based on this information. The mecha-
nism for the reaction of an aromatic compound occurs
through one of two mechanisms, the compound can be
modified with substituents with different ρ values and
kinetic measurements taken. Once these measurements
have been made, a Hammett plot can be constructed
to determine the value of ρ. If one of these mecha-
nisms involves the formation of charge, this can be
verified based on the ρ value. The values of ρ+ and
ρ− at five different temperatures are given in Table
V (aniline moiety). The unsubstituted anil is the most
reactive in this series. But both the electron-releasing
and -withdrawing substituents retard the rate of the re-
action considerably. The electron attractors can retard
the reaction rate only when there is a development of
positive charge in the transition state:
Hammett Plot for the Aniline Moiety
Hammett made a unique discovery [45] about the linear
free energy relationships for the side chain. The type of
concave upward and concave downward curves in the
Hammett plot has been reported earlier [46]. The con-
cave downward curve was obtained for the anils with
substituents in the aniline moiety (Fig. 4). The electron-
releasing substituents fall on the one side of the curve
with a positive slope and the electron-withdrawing sub-
stituents on the other side with a negative slope. The
6.5
m-NO
6.0
5.5
5.0
4.5
4.0
3.5
3.0
H
m-Cl
p-CH
p-Cl
p-OC H
p-NO
m-CH
p-OCH
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
σ
Figure 4 Hammett plot for PPMS oxidation of aromatic
anils (substitution in the aniline moiety) at 298 K.
International Journal of Chemical Kinetics DOI 10.1002/kin.20794

548
VENKATESH AND KARUNAKARAN
Since the electron-releasing substituents also retard
the rate of the reaction, the rate-determining step pro-
ceeds with the development of negative charge on the
nitrogen atom of anil:
It is to be noted that this kind of transition state has
been suggested in the oxidation of sulfides by pyri-
dinium chlorochromate (PCC) [47] and pyridinium
dichromate (PDC) [48] and anil by isonicotinium
dichromate (INDC) [36]. Gurunathan et al. [36] have
established the order dependence with respect to the
reactants and other kinetic parameters of anils (sub-
stitution only in the aniline moiety). The formation of
oxalatochromate species is reported as the intermediate
of the reaction since oxalic acid is used as a catalyst.
Hammett Plot for a Combination of Aniline
and Benzaldehyde Moieties
The concave upward curve was obtained for the anils
with substituents in a combination of aniline and ben-
zaldehyde moiety (Fig. 6), suggesting that the electron-
releasing substituents fall on the one side of the curve
with a negative slope and the electron-withdrawing
substituents on the other side with a positive slope like
in substituents only in the benzaldehyde moiety.
Hammett Plot for the Benzaldehyde Moiety
22
p-OCH
The concave upward curve was obtained for the anils
with substituents in the benzaldehyde moiety (Fig. 5).
The electron-releasing substituents fall on the one side
of the curve with a negative slope and the electron-
withdrawing substituents on the other side with a pos-
itive slope. The isokinetic and Exner plots reveal that
there is no change in the reaction mechanism with re-
spect to the substituents in the benzaldehyde moiety.
The values of ρ+ and ρ− at five different tempera-
tures are given in Table V (benzaldehyde moiety). The
unsubstituted anil is also the less reactive in this se-
ries. But both the electron-releasing and -withdrawing
substituents accelarate the rate of the reaction consid-
erably, dissimilar to the aniline moiety. This shows the
opposite kind of behavior compared with the aniline
moiety.
20
18
16
p-OC H
14
12
p-NO
p-CH
m-CH
10
8
m-NO
m-Cl
6
H
p-Cl
4
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
σ
Figure 5 Hammett plot for PPMS oxidation of aromatic
anils (substitution in the benzaldehyde moiety) at 308 K.
International Journal of Chemical Kinetics DOI 10.1002/kin.20794

KINETIC INVESTIGATION OF OXIDATION OF AROMATIC ANILS BY PPMS
549
6. Secco, F.; Venturini, M. J Chem Soc, Dalton Trans 1976,
1410.
7. Ramchandran, M. S.; Vivekanandam, T. S.;
Arunachalam, V. Bull Chem Soc Jpn 1986, 59,
1549.
11
10
9
p-OCH
8. Balahura, R. J.; Johnson, M. D. Inorg Chem 1988, 7,
3104.
8
p-Cl
9. Ramachandran, M. S.; Vivekanandam, T. S.; Paul,
N.; Singh, D. Indian J Chem A 1988, 27, 498.
10. Betterton, E. A.; Hoffmann, M. R. Environ Sci Technol
24, 1990, 1819.
7
m-NO
p-OC H
6
5
m-Cl
11. Venkatasubramaniam,
Maruthamuthu, P. Int
69.
L.;
Dharmalingam,
P.;
p-CH
H
J
Chem Kinet 1990, 22,
4
m-CH
p-NO
3
12. Gilbert, B. C.; Stell, J. K. J Chem Soc, Perkin Trans
1991, 2, 1105.
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
13. Spiro, M. Electrochem Acta 1979, 24, 313.
14. Jameel, A. A.; Maruthamuthu, P. J Indian Chem Soc
1998, 75, 368.
15. Panda, R. S.; Pradhan, S. C. J Indian Chem Soc 2000,
77, 315.
σ
Figure 6 Hammett plot for PPMS oxidation of aromatic
anils (substitution in a combination of aniline and benzalde-
hyde moieties) at 298 K.
16. Nolan, A. L.; Burns, R. C.; Lawrance, G. A. J Chem
Soc, Dalton Trans 1996, 2629.
17. Nolan, A. L.; Burns, R. C.; Lawrance, G. A. J Chem
Soc, Dalton Trans 1998, 3041.
CONCLUSIONS
18. Sallam, S. A. Transit Met Chem 2006, 31, 46–55.
19. Snatos, J. E.; Dockal, E. R.; Cavalheiro, E. T. G. J Therm
Anal Calorim 2005, 79, 243–248.
20. Clarkson, S. G.; Basolo, F. Inorg Chem 1973, 12, 1528–
1534.
21. Li-xia, Z.; Yi, L.; Li-hua, C.; Yan-jun, H.; Jun, Y.;
Pei-zhi, H. Thermochim Acta 2006, 440, 51–56.
22. Tarafder, M. T. H.; Kasbollah, A.; Saravanan, N.;
Crouse, K. A.; Ali, A. M.; Tin.; Ook. J Biochem Mol
Biol Biophys 2002, 6, 85–91.
23. Mcneill, J. H.; Yuen, V. G.; Hoveyda, H. R.; Orvig, C. J
Med Chem 1992, 35, 1489–1491.
24. Panchagnula, R.; Sharma, P.; Kandavilli, S.; Varma, M.
V. S.; Il Farmaco 2004, 59, 839–842.
25. Vicini, P.; Geronikaki, A.; Incerti, M.; Busonera, B.;
Poni, G.; Cabras, C. A.; Colla, P. L.; Bioorg Med Chem
2003, 11, 4785–4789.
The reaction followed first-order kinetics with respect
to the concentration of [anil], PPMS, and [acid], re-
spectively. Under the experimental conditions, aro-
matic anil is oxidized to benzaldehyde and azobenzene.
The high negative entropy of activation suggested that
the formation of a complex is a slow step. The concave
downward curve of the Hammett plot was obtained
for the anils with substituents in the aniline moiety,
whereas the concave upward curve was observed for
the substituents in the benzaldehyde moiety and for
the substituents in the combination of aniline and ben-
zaldehyde moieties. The oxidation can also be analyzed
for special types of drugs.
26. Pignatello, R.; Panico, A.; Mazzone, P.; Pinizzotto, M.
R.; Garozzo, A.; Fumeri, P. M. Eur J Med Chem 1974,
29, 781–785.
27. Singh, B. K.; Prakash, A.; Rajouir, H. K.; Bhojak, N.;
Adhikari, D. Spectrochim Acta A 2010, 76, 376–383.
28. Catto, A.; Corbani, F.; Rindone, B.; Scolastico, C.
Tetrahedron Lett 1973, 29, 2723.
29. Rindone, B.; Scolastico, C. J Chem Soc, Perkin Trans I
1975, 20, 2022.
30. Narasimha Bharathi, S.; Sundaram, E. V.;
Venkatasubramanian, N. V. Indian J Chem B 1977, 15,
376.
BIBLIOGRAPHY
1. Meunier, B. New J Chem 1992, 16, 203–211.
2. Betterton, E. A.; Hoffmann, M. R. Environ Sci Technol
1990, 24, 1819–1824.
3. Kennedy, R. J.; Stock, A. M. J Org Chem 1960, 25,
1901–1906.
4. (a) Yang, D.; Zhang, C. J Org Chem 2000, 66, 4814;
(b) Bolm, C.; Magnus, A. S.; Hildebrand, J. P. Org Lett
2000, 2, 1173; (c) Travis, B. R.; Sivakumar, M.; Hollist,
G. O.; Borhan, B. Org Lett 2003, 5, 1031; (d) Plietker,
B. Org Lett 2004, 6, 289; (e) Singh, R.; Kissling, R.
M.; Letellier, M. A.; Nolan, S. P. J Org Chem 2004, 69,
209;(f) Ge, H. Q Synlett 2004, 11, 2046.
31. Narasimha Char, P.; Sethuram, S.; Navaneeth Rao, T.
Indian J Chem A 1988, 27A, 31.
32. Ramesh, S.; Umesh, N.; Dodwad, S. S. Asian J Chem
1997, 9(2), 195.
5. Anbar, M.; Taube, H. J Am Chem Soc 1954, 76, 6243.
International Journal of Chemical Kinetics DOI 10.1002/kin.20794

550
VENKATESH AND KARUNAKARAN
33. Karthikeyan, G.; Elango, K. P.; Karunakaran, K.;
Balasubramanian, A. Oxid Commun 1998, 21(1), 51.
34. Umesh, N.; Ramesh, S.; Dodwad, S. S. Asian J Chem
1997, 9(1), 58.
35. Karunakaran, K.; Nagarajan, S.; Kanagavel, D.;
Jegadish, T. N.; Palanisamy, P. N.; Elango, K. P. Oxid
Commun 1997, 20(4), 576.
41. Kuttirani, S.; Nirmal Kumar, S.; Crystal, Y.; Wilson,
A.; Gopi, D.; Eswaramoorthy, J. Eng Chem 2009, 15,
898.
42. Dubey, S.; Hemkar, S.; Khandelwal, C. L.; Sharma,
P. D. Inorg Chem Commun 2002, 5, 903.
43. Karthikeyan, G.; Elango, K. P.; Karunakaran, K. J Indian
Chem Soc 1997, 74, 798–799.
36. Ramalingam, G.; Jayanthi, S. Transit Met Chem 2007,
32, 475–480
37. Ramalingam, G.; Jayanthi, S.; Gopalakrishnan, M. Oxid
Commun 2006, 29(3), 684.
38. Campbell, K. N.; Sommers, A. H.; Campbell, B. K. J
Am Chem Soc 1944, 66, 82.
44. Karthikeyan, G.; Elango, K. P.; Karunakaran, K.;
Balasubramanian, A. Oxid Commun 1998, 21(1), 51–
54.
45. Hammett, L. P. J Am Chem Soc 1937, 59, 96.
46. Mahadevappa, D. S.; Pattusamy, Indian J Chem A 1990,
29, 42.
39. Bhuvaneshwari, D. S.; Elango, K. P. Z Phys Chem 2006,
220, 697.
47. Rajasekaran, K.; Baskaran, T.; Gnanasekaran, C. Indian
J Chem A 1987, 26, 956.
40. Karunakaran, C.; Palanysamy, P. N. Int J Chem Kinet
1999, 31, 571.
48. Mangalam, G.; Meenakshisundaram, S. P. J Indian
Chem Soc 1991, 68, 77.
International Journal of Chemical Kinetics DOI 10.1002/kin.20794