Meso-tetraphenylironporphyrin(III) chloride catalyzed oxidation of aniline and its substituents by m-chloroperbenzoic acid

Article abstract of DOI:10.4067/S0717-97072012000400005

The most fascinating feature of heme-enzymes such as cytochromes P450 is their ability to carry out oxidations with high selectivity. Metalloporphyrin complexes are used as replicate compounds for cytochrome P450. A kinetic analysis has been carried out with the aim of understanding the mechanistic studies on oxidation of anilines by m-chloroperbenzoic acid catalyzed by meso-tetraphenylironporphyrin(III) chloride in aqueous acetic acid medium. The order of the reaction is found to be second order with respect to the substrate and first order with respect to the catalyst and oxidant. Product analysis proves that azobenzene is the sole product in the catalytic oxidation. The increase of [H⁺] in this oxidation retards the rate of the reaction. The effects of substituents on the oxidation rate are studied with 19 ortho-, meta- and para- substituted anilines at five different temperatures. The thermodynamic parameters for the oxidation have been determined and discussed. The catalysed m-chloroperbenzoic acid oxidation with substituted anilines fulfills the isokinetic relationship and Exner correlation but not to any of the linear free energy relationships. The solvent interaction also plays a major role in leading the reactivity. Based on the kinetic results and product analysis a probable mechanism is proposed.

Full text of DOI:10.4067/S0717-97072012000400005

J. Chil. Chem. Soc., 57, Nº 4 (2012)
meso-TETRAPHENYLIRONPORPHYRIN(III) CHLORIDE CATALYZED OXIDATION OF ANILINE AND ITS
SUBSTITUENTS BY m-CHLOROPERBENZOIC ACID
M. RAJA , K. KARUNAKARAN*
Department of Chemistry, Sona College of Technology, Salem - 636005, India.
(Received: August 5, 2011 - Accepted: April 21, 2012)
ABSTRACT
The most fascinating feature of heme-enzymes such as cytochromes P450 is their ability to carry out oxidations with high selectivity. Metalloporphyrin
complexes are used as replicate compounds for cytochrome P450. A kinetic analysis has been carried out with the aim of understanding the mechanistic studies
on oxidation of anilines by m-chloroperbenzoic acid catalyzed by meso-tetraphenylironporphyrin(III) chloride in aqueous acetic acid medium. The order of the
reaction is found to be second order with respect to the substrate and first order with respect to the catalyst and oxidant. Product analysis proves that azobenzene is
the sole product in the catalytic oxidation. The increase of [H+] in this oxidation retards the rate of the reaction. The effects of substituents on the oxidation rate are
studied with 19 ortho-, meta- and para- substituted anilines at five different temperatures. The thermodynamic parameters for the oxidation have been determined
and discussed. The catalysed m-chloroperbenzoic acid oxidation with substituted anilines fulfills the isokinetic relationship and Exner correlation but not to any
of the linear free energy relationships. The solvent interaction also plays a major role in leading the reactivity. Based on the kinetic results and product analysis a
probable mechanism is proposed.
Key words: Aniline, oxidation, m-chloroperbenzoic acid, meso-tetraphenylporphyriniron(III) chloride.
show that the rate constants for oxidation reactions are reproducible within
+ 3%. The reaction is also carried out using acrylonitrile to find the presence
of free radical mechanism. ortho-, meta- and para- substituents of aniline are
redistilled / recrystallized before use. The oxidation reactions of meta- and
para- substituents of aniline were studied at different temperatures via 292,
296, 300, 305.5, and 312 K to assess various thermodynamic parameters.
INTRODUCTION
Metalloporphyrin complexes are extensively used as mimetic compounds
for the catalytic activity of cytochrome P450 enzymes in life process1.
Metalloporphyrins have been the subjects of a number of findings as they
act as a selective catalyst. The relations between the oxygen donor and the
metal centre of the catalyst form a high valent metal oxospecies which can
act as a useful oxidising agent and is capable of transferring the oxygen atom
to the substrate2. Many mechanistic studies3-11 have revealed that halogenated
metalloporphyrin complexes are excellent catalysts for difficult oxidations with
high selectivity. The potential of the heme group is to merge with tiny ligands
(including molecular oxygen) in enzymatic oxidations. The contribution of
heme in these oxidation processes has motivated chemists to proceed from
these naturally occurring catalysts and to use them into industrial processes. In
order to learn the core of the heme group, the porphyrin ring with the central
metal iron atom has been selected. The iron complexes with meso-tetraphenyl
groups are broadly considered as replicate of the natural ironporphyrins due
to their useful properties such as catalytic and semi-conducting properties.
Iron complexes of tetraphenylporphyrins can be regarded as macrocyclic
ligands that has an intermediate structure sandwiched between common
natural iron porphyrins with cytochrome P450. To complement the studies
in the field of the catalytic oxidation of aniline, the oxidation of aniline by
m-chloroperbenzoic acid catalysed by first generation porphyrin catalyst
meso-tetraphenylporphyriniron(III) chloride (5,10,15,20-tetraphenyl-21h,23h-
porphineiron(III) chloride) has been selected for the research. A literature
survey 12 reveals that the oxidation of anilines by a range of oxidants has been
reported and only some of them authenticate Hammet equation. This is due to
the fact that aniline in acid medium exists in dual forms, that is as free bases
and as conjugate acids.
From the Eyrings equation13, the thermodynamic parameters enthalpy of
activation and entropy of activation are figured out from the expression
kobs = (kbT/h)exp-ΔG#/RT
Where kb is Boltzmann’s constant, T is the temperature in Kelvin, h is
plank’s constant, R is the gas constant , ΔG# is the activation of Gibbs free
energy, ΔH# is the enthalpy of activation and ΔS# is the entropy of activation.
ΔG# and energy of activation (Ea) can be calculated from the following
expressions respectively.
ΔG# = ΔH# - TΔS# and Ea = ΔH# + RT
DATA ANALYSIS
Correlation studies are carried out using Microcal Origin (version 6)
and SPSS computer software. The goodness of the fit is discussed using the
correlation coefficient, r in the case of simple linear regression and R in the
case of multiple linear regressions.
STOICHIOMETRY AND PRODUCT ANALYSIS
The stoichiometry of the reaction is found out by doing several sets of
experiments by varying [m-chloroperbenzoic acid] in the range of 0.1-1.5M
([substrate] = 0.1M, [catalyst] = 1.4x10-6M, acetic acid:water = 60:40, [H+] =
0.2N, temperature = 300 K). The estimation of unconsumed m-chloroperbenzoic
acid shows that the stoichiometry of the reaction is found to be in the
ratio of 1:2 (m-chloroperbenzoic acid : aniline). The oxidation product is
confirmed using TLC. Under the pseudo-first order condition [aniline]>>[m-
chloroperbenzoic acid] in acetic acid medium, the product obtained is followed
spectrophotometrically at 429 nm which is the λmax of azobenzene. This is in
agreement with the literature value14.
EXPERIMENTAL
The catalyst meso-tetraphenylporphyriniron(III) chloride (Sigma
Aldrich) has been used as received. All chemicals and solvents used are of
analytical grade (Merck, India). Aniline is redistilled before use. Acetic
acid is purified by redistillation. All the reagents has been prepared fresh
just before the reactions are carried out. A solution of m-chloroperbenzoic
acid in acetic acid was prepared fresh and standardized iodometrically. The
kinetic studies have been carried out under pseudo-first-order conditions with
the [substrate] >> [m-chloroperbenzoic acid]. Kinetic studies are done with
aniline by varying the concentration of aniline, m-chloroperbenzoic acid,
meso-tetraphenylporphyriniron(III) chloride, acetic acid, H+ and by varying
temperature. All the reactions have been carried out in a thermostat and the
temperature is controlled to + 0.1oC. The progress of the oxidation reaction is
followed by determining the amount of unconsumed m-chloroperbenzoic acid
iodometrically up to 80% of completion of the reaction at different reaction
time. The rate constants (kobs) have been found out by the least square slopes
of the linear plots of log[m-chloroperbenzoic acid] and time. Repeated runs
RESULTS AND DISCUSSION
EFFECT OF VARIATION OF SUBSTRATE CONCENTRATION
At fixed concentrations of m-chloroperbenzoic acid and H2SO4, the
increase in concentration of substrate (aniline) increases the rate of the reaction.
The plot in the Fig. 1, that is log kobs vs log[aniline] was found to be a straight
line with slope two. This reveals that the reaction is second order with respect
to the substrate.
e-mail: drkk@sonatech.ac.in
1355

J. Chil. Chem. Soc., 57, Nº 4 (2012)
Fig. 1. Plot of logkobs versus log[aniline] for the oxidation of aniline by
m-chloroperbenzoic acid catalysed by meso-tetraphenylporphyriniron(III)
chloride. [oxidant] = 0.005M, [catalyst] = 1.4x10-6M, acetic acid:water =
60:40, [H+]=0.2N, temperature = 292K
Fig. 2.Plot of logk versus log[H+] for the oxidation of aniline by
m-chloroperbenzoic aciodbs catalysed by meso-tetraphenylporphyriniron(III)
chloride. [substrate] = 0.1M, [oxidant] = 0.005M, [catalyst] = 1.4x10-6M, acetic
acid:water = 60:40, temperature = 300 K
EFFECT OF VARIATION OF m-CHLOROPERBENZOIC ACID
CONCENTRATION
When the concentration of the substrate is constant, the increase in
concentration of m-chloroperbenzoic acid does not affect the apparent rate
constant of the reaction (Table 1). The first order plot of log[m-chloroperbenzoic
acid] vs time is found to be linear. The pseudo-first order rate constants found
from the plots are unaltered by the change in [m-chloroperbenzoic acid] which
confirmed the first order dependence of the reaction rate on m-chloroperbenzoic
acid.
Table1.Pseudo-firstorderrateconstantsfortheoxidationofanilinebyvarying
[m-chloroperbenzoic acid] catalysed by meso-tetraphenylporphyriniron(III)
chloride.
[oxidant] (M)
0.006
105 kobs (s-1)
3.57
0.007
3.44
Fig. 3. Plot of logkobs versus log[meso-tetraphenylporphyriniron(III)
chloride] for the oxidation of aniline by m-chloroperbenzoic acid catalysed by
meso-tetraphenylporphyriniron(III) chloride. [substrate] = 0.1M, [oxidant] =
0.005M, acetic acid:water = 60:40, [H+] = 0.2N, temperature = 300K.
0.008
3.52
0.009
3.49
0.010
3.48
EFFECT OF VARIATION IN TEMPERATURE
The oxidation of aniline is studied at different temperatures via 292, 296,
300, 305.5 and 312 K maintaining the concentration of substrate, oxidant, H+,
solvent and catalyst constant. The plot of lnkobs/T vs 1/T (Fig. 4) is found to
be linear.
[substrate] = 0.1M, [catalyst] = 1.4x10-6M, acetic acid:water = 60:40, [H+]
= 0.2N, temperature = 300 K
EFFECT OF VARIATION OF H+ CONCENTRATION
The reaction rate on the variation of hydrogen ion concentration has been
determined at different initial concentrations and keeping the concentrations of
the other reactants constant. The proton concentration is equated to the sulfuric
acid concentration. The rate of the reaction decreases with increase in H2SO4
concentration. The plot (Fig. 2) logkobs vs log[H+] gives a straight line with
unit slope which is inversely proportional to the proton concentration. Aniline
in acid medium exists in dual forms, the free bases and conjugate acids, that
is protonated (C6H5NH3+) and nonprotonated aniline (C6H5NH ). The literature
study23 reveals that the reaction of aniline proceeds through2 protonated and
unprotonated form of aniline and the (increase in [H+] increases the reaction
rate) protonated aniline is more reactive in 3-butyn-2-one. But in the present
study increase in [H+] leads to the decrease in reaction rate. (Increase of
protonated aniline inhibits the reaction rate) This reveals that the protonated
aniline is less reactive in this oxidation reaction.
EFFECT OF VARIATION IN CATALYST CONCENTRATION
The oxidation of aniline by m-chloroperbenzoic acid in acetic acid is very
slow but when catalysed by meso-tetraphenylironporphyrin(III) chloride the
reaction rate increases. But the plot (Fig. 3) of logkobs vs log[catalyst] is found
to be linear with a unit slope which indicates a first order dependence with
respect to catalyst.
Fig. 4. Plot of lnkobs/T versus 1/T for the oxidation of aniline by
m-chloroperbenzoic acid catalysed by meso-tetraphenylporphyriniron(III)
chloride. [substrate] = 0.1M, [oxidant] = 0.005M, [catalyst] = 1.4x10-6M, acetic
acid:water = 60:40, [H+] = 0.2N
1356

J. Chil. Chem. Soc., 57, Nº 4 (2012)
The values of thermodynamic parameters have been found as ΔH# = 15.07
kJ mol-1, ΔS# = -279.02 J K-1 mol-1, ΔG# = 99.34 kJ mol-1 and Ea = 17.59 kJ mol-1
K-1. The high, negative, entropy of activation is compatible with the high (total)
order of the reaction.
activation enthalpy versus activation entropy follows a straight line as shown
in the Fig. 6. The function of isokinetic relationship15,16 reveals that a common
mechanism is working in all the aniline oxidation reactions13. Isokinetic
temperature is the temperature at which all the compounds react at same speed
since this temperature variation of substituent has no influence on the free
energy of activation. In an isoentropic oxidation, the isokinetic temperature
lies at infinite and only enthalpy of activation determines the reactivity. The
isokinetic temperature is zero for an isoenthalphic series and the reactivity is
determined by the entropy of activation12.
EFFECT OF DIELECTRIC CONSTANT
The effect of solvent on the reaction rate is studied by varying the
composition of acetic acid from 40% to 80% (Table 2). The oxidations are
carried out by maintaining the concentration of aniline, m-chloroperbenzoic
acid, catalyst and temperature constant. The above observation clearly reveals
that the rate decreases with increase in percentage of acetic acid, i.e. with
decreasing dielectric constant (D) or polarity of the medium. This directs to
the conclusion that there is a charge development in the intermediate state
involving a more polar intermediate than reactants, suggesting a polar (ionic)
mechanism.
ΔH# = ΔHo + βΔS#
β is the isokinetic temperature which is found to be 329K and it is greater
than the experimental temperature.
Table 2. Pseudo-first order rate constants for the oxidation of aniline
by m-chloroperbenzoic acid catalysed by meso-tetraphenylporphyriniron(III)
chloride in different acetic acid compositions.
% Acetic acid
D
105 kobs (s-1)
26.70
10.10
5.14
40
50
60
70
80
49.60
42.37
35.14
27.90
20.67
3.04
1.80
[substrate] = 0.1M, [oxidant] = 0.005M, [catalyst] = 1.4x10-6M, [H+] =
0.2N, temperature = 312K
Fig. 6. Isokinetic plot for the meso-tetraphenylporphyriniron(III) chloride
catalysed oxidation of anilines by m-chloroperbenzoic acid.
The values of free energy of activation of the reactions are found to be
more or less similar. This is due to the fact that at isokinetic temperature the
change of substituent has no influence on the free energy of activation. If the
isokinetic temperature is infinite in isoentropic oxidation reactions, only the
enthalpy of activation finalizes the reactivity and if the isokinetic temperature is
zero in isoenthalpic oxidation reactions, only the entropy of activation finalizes
the reactivity10.
Fig. 5. UV spectrum showing a probable formation of intermediate
complex in oxidation of aniline by m-chloroperbenzoic acid catalysed by meso-
tetraphenylporphyriniron(III) chloride.
Fig. 5 shows the UV spectrum at early stages and final stages of the
oxidation reaction. At initial stages of the reaction a new peak at 717 nm
appeares, slowly diminishes and vanishes at the final stages of the reaction.
This may be due to the formation of an intermediate from which products are
formed. Simultaneously, at 429 nm, a peak appears and is stable till the end
of the reaction. The may be due to the formation of the product which is in
agreement with literature value14 (429 nm is the λmax of azobenzene in acetic
acid medium).
SUBSTITUENTS EFFECT
The kinetics and oxidation of aniline and o–OCH , m–OCH , p–OCH3,
o–CH3, m–CH3, p–CH3, o–Cl, m–Cl, p-Cl, o–Br, m3–Br, p-Br,3o–F, m–F,
p-F, o–NO2, m–NO2, p–NO anilines in the presence of catalyst are conducted
under pseudo-first order co2nditions at various temperatures 292 K, 296 K,
300 K, 305.5 K and 312 K to determine various thermodynamic parameters.
The various thermodynamic parameters ΔH#, ΔS#, ΔG# and Ea are found and
tabulated (Table 3). The analysis of the data in the Table 3 indicates that the
oxidation is neither isoenthalphic nor isoentropic but confirms with isokinetic
relationship of compensation law. Since the reactions are of ion-polar, it is
expected that the entropy of the activated complex for all the anilines should
be nearly the same order of magnitude. But due to the variation in polarity of
different anilines, ΔS# may be different for different anilines12,, as observed
in the present findings. But the isokinetic relationship exists. The plot of
Fig. 7. Exner plot for the meso-tetraphenylporphyriniron(III) chloride
catalysed oxidation of anilines by m-chloroperbenzoic acid.
The Exner relationship (Fig. 7), the linear double logarithmic relationship
between the rates at different temperatures, also confirms the common
mechanism throughout the series.
STRUCTURE-REACTIVITY CORRELATION
The outcome in the Table 3 reveals that the ΔG# values differ with
substrate. This may be due to the difference in polarity of various anilines. So
the obtained rate constants show deviation with substituents. Negative entropy
of activation also gives the information that the complex formed is an associate
type with a greater degree of charge in transition state than initial state13.
1357

J. Chil. Chem. Soc., 57, Nº 4 (2012)
Table 3. Pseudo-first order rate constants for meso-tetraphenylporphyriniron(III) chloride catalyzed m-chloroperbenzoic acid oxidation of meta- and para-
substituted anilines at different temperatures, thermodynamic and activation parameters.
105 kobs (s-1)
ΔH#
kJ
-ΔS#
J K-1
mol-1
ΔG#
kJ
Ea
kJ mol-1
K-1
Aniline
substituents
r
mol-1
mol-1
292 K
296 K
300 K
305.5 K
312K
o–OCH3
o–CH3
o–Cl
18.17
2.91
22.30
3.71
27.91
4.06
31.61
4.57
48.61
6.04
33.27
23.07
76.67
30.69
76.67
33.84
62.75
44.13
51.45
89.52
66.55
59.02
51.93
53.59
52.51
101.0
76.67
46.67
15.08
-203.00
-252.72
-56.20
-200.44
-56.20
-192.05
-120.03
-188.58
-15.54
-32.11
94.58
99.39
93.64
91.22
93.64
91.84
98.99
101.1
98.39
99.21
96.23
95.02
97.57
102.3
98.17
99.46
93.64
96.02
99.34
35.78
25.58
79.18
33.20
79.18
36.35
65.26
46.64
53.95
92.03
69.06
61.53
54.44
56.10
55.03
103.5
79.18
49.18
17.59
0.987
0.981
0.997
0.986
0.998
0.994
0.997
0.997
0.988
0.991
0.997
0.987
0.997
0.993
0.999
0.987
0.997
0.998
0.998
15.90
74.00
40.15
54.05
2.30
23.61
87.43
47.99
66.50
3.07
37.94
93.35
62.05
76.73
4.29
59.13
128.62
78.09
105.60
7.28
130.57
176.84
113.97
fast
o–Br
o–F
o–NO2
m–OCH3
m–CH3
m–Cl
m–Br
m–F
12.25
4.12
1.24
1.50
1.91
2.81
2.97
4.65
5.50
9.32
12.25
17.14
40.45
29.92
187.83
2.80
1.32
2.79
4.08
6.50
6.39
9.40
12.84
13.77
62.32
1.25
20.34
23.91
112.06
1.70
-98.28
-119.2
m–NO2
p–OCH3
p–CH3
p–Cl
8.80
11.28
39.56
0.95
23.85
0.60
-151.15
-161.39
-151.17
5.18
3.45
4.54
6.34
9.51
14.29
17.45
8.37
p–Br
1.02
2.07
4.52
6.14
p–F
0.39
0.74
1.68
3.77
-56.20
-163.47
-279.02
p-NO2
H
77.16
3.41
102.37
3.72
109.67
4.17
183.03
4.73
fast
5.36
[substrate] = 0.1M, [oxidant] = 0.005M, [catalyst] = 1.4x10-6M, acetic acid:water = 60:40, [H+] = 0.2N
The rate data obtained is also unsuccessful in proving that the typical
Hammet equation logkobs vs σ is a dispersed gram and a sensitive plot (Fig. 8)
at the temperatures studied. Substituents p–OCH3, m–NO2, p–CH3, m–CH3, m–
Cl, p–Cl, p–Br, are found to be deviating largely. The correlation coefficient
(r) of the dispersed gram is found to be 0.461 with standard deviation of 0.565.
Literature study17 also reveals that correlation obtained with it are poor as the
substituents are conjugated with the reaction centre, where the problem arose
with anilinium ions, where a lone pair of electrons on the NH2 group can be
delocalized into substituents such as p-NO2.
The correlation of oxidation rates of meta– and para– substituted anilines
are correlated separately with any of the unit parameters (meta: σ, σm+ ; para:
σ, σp+, σp-) and is also found to be ineffective. The oxidation rates measured
at 292, 296, 300, 305.5 and 312K are analysed in terms of dual substituent
-
+
parameter equations (meta: σI, σR; σI, σR ; σI, σR ; F, R; para: σI, σR ; σI,
+
σR- ; σ , σR ; F, R) and is also found to be unsuccesful. The pKa of anilines
changeIs with substituents (1.59 for p-cyano to 6.08 for p-amino) so that the
concentration of the substituted protonated aniline varies. This strongly affects
the rate of the reaction. So the correlations are found to be unsuccessful.
Fig. 8. Hammet plot for the meso-tetraphenylporphyriniron(III) chloride
catalysed oxidation of anilines by m-chloroperbenzoic acid.
1358

J. Chil. Chem. Soc., 57, Nº 4 (2012)
The possible reason for the lack of free energy relationship is the isokinetic
temperature 329 K which is greater than the experimental temperature. The
same type of results is also reported by Elango and Buvaneswari18. Operation of
inductive and resonance effect opposing each other is known19 but the present
study has no parallel. The less pronounced substituent can be explained only by
the compensation effect. Aniline in basic and neutral media is present as free
bases but in acid medium it exists in dual forms the free bases and conjugate
acids19. The stoichiometry of the findings shows that two aniline molecules are
involved in the reaction. This shows that the catalyst-aniline complex is likely to
be the electrophile and free aniline may be the nucleophile. The influence of the
substituents on the reactivity of the nucleophile is approximately compensated
by the influence of the same substituent on the reactivity of the electrophile13.
In some of the substituted aniline, exact compensation is doubtful and the
resultant effect is experienced on the oxidation rate.
polymer) in the oxidation of aniline. This rules out the presence of free radical
mechanism in this oxidation reaction. So the ionic reaction is preferred in this
oxidation study. Generally, the enhancement of the electrophillic activity of
peroxide will minimize the importance of undesirable free radical pathways,
resulting in a mixture of products20. In acetic acid medium, catalyst–oxidant
adduct is formed first, which then decomposes to evolve oxoiron(V) species
which is the major reactive intermediate. The proposed route of the formation
of the reactive intermediate is represented in the first step of the mechanism
(Scheme 1). Literature study21 also confirms the formation of the same catalyst–
oxidant adduct. The investigation results illustrate a fascinating note that H+
retards the rate of the reaction. This gives the evidence that H+ ion is released
in the rate determining step. No Hammet equation originates in the substituents
effect. The results can be explained by the formation of intermediate complex.
Usually peroxy ions act as strong nucleophiles.
MECHANISM
Based on the stoichiometry of the reaction and above experimental
outcomes, the following reactions (scheme 1) are considered to constitute the
most probable mechanism of the reaction.
The known fact is that the free radicals can be produced by the homolytic
fission of peroxide bond. But the addition of acrylonitrile monomer shows no
variation in the reaction rate and no formation of turbidity (no formation of
Scheme 1. Probable mechanism for the meso-tetraphenylironporphyrin(III) chloride catalysed oxidation of aniline by m-chloroperbenzoic acid.
The formation of the first intermediate and the formation of Por-Fev=O
REFERENCES
are in agreement with the literature study22 and the intermediate formed is
experimentally confirmed at 717 nm. The third step is a slow reaction and is
likely to be the rate determining step.
1. Qingzhang Lu, Ruqin Yu, Guoli Shen, J. Mol. Catal. A-Chem., 198, 9,
(2003).
RATE LAW
2. Sandro Campestrini, Alessandro Cagnina, J. Mol. Catal. A-Chem., 150,
77 (1999).
The above suggested mechanism leads to the rate law which is in agreement
with the experimental findings.
3. Yassuko Iamamoto, Cynthia M.C. Prado, Herica C. Sacco, Katia J. Ciuffi,
Marilda D. Assis, Ana Paula J. Maestrin, Andrea J.B. Melo, Oswaldo
Baffa, Otaciro R. Nascimento, J. Mol. Catal. A-Chem., 117, 259 (1997).
4. S. Tollari, A. Fumagalli, F. Porta, Inorg. Chim. Acta., 247, 71 (1996).
5. Zeev Gross, Liliya Simkhovich, J. Mol. Catal. A-Chem., 117, 243, (1997).
6. Fabiana C. Skrobot, Ieda L. V. Rosa, Ana Paula A. Marques, Patricia R.
Martins, J. Rocha, Anabela A.Valente, Yassuko Iamamoto, J. Mol. Catal.
A-Chem., 237, 86 (2005).
7. Dorota Rutkowska-Zbik, Malgorzata Witko, J. Mol. Catal. A-Chem., 258,
376 (2006).
8. Eva R. Birnbaum, Richard M. LE Lacheur, April C. Horton, William
Tumas, J. Mol. Catal. A-Chem., 139, 11 (1999).
9. Denise Abatti, M. Elisabete D. Zaniquelli, Yassuko Iamamoto, Ynara M.
Idemori, Thin Solid Films, 310, 296 (1997).
10. Tina M. Nenoff, Margaret C. Showalter, Kenneth A. Salaz, J. Mol. Catal.
A-Chem., 121, 123 (1997).
11. S. M. S. Chauhan, P. P. Mohapatra, Bhanu Kalra, T. S. Kohli, S. Satapathy,
J. Mol. Catal. A-Chem., 113, 239 (1996).
12. C. Karunakaran, P. N. Palanisamy, Gazzetta Chimica Italiana, 127, 559
(1997).
-d[oxidizing agent] = K1K2 K3K4k5[PhNH2]2 [PorFeIIICl] [oxidizing agent]
dt
[H+]2
CONCLUSION
The oxidation of aniline by meso-tetraphenylporphyriniron(III) chloride is
second order with respect to the substrate, first order with respect to the oxidant
and first order with respect to the catalyst. The addition of H+ ions retards the
rate of the reaction. The rate data obtained is also unsuccessful in proving the
Hammet equation. The correlations of oxidation rates substituted anilines are
correlated separately with any of the unit parameters which is also found to be
ineffective. The oxidation rates analysed in terms of dual substituent parameter
equations is also found to be unsuccessful. Solvent interaction also plays
an important role in leading the reactivity. Suitable mechanism is proposed
for the catalysed oxidation reaction. The strength of isokinetic relationship
and various free energy relationships have been related and discussed. With
m-chloroperbenzoic acid as oxygen donor, the first generation ironporphyrin
catalyst is proved to be a more effective catalyst in oxidising aniline.
13. D. S. Bhuvaneshwari, K. P. Elango, Z. Phys. Chem., 220, 697 (2006).
1359

J. Chil. Chem. Soc., 57, Nº 4 (2012)
14. Chockalingam Karunakaran, Ramasamy Kamalam, J. Chem. Soc., Perkin
Trans., 2, 2011 (2002).
15. D. S. Bhuvaneshwari, K. P. Elango, J. Indian Chem. Soc., 86, 242 (2009).
16. Durvas S. Bhuvaneswari, Kuppanagounder P. Elango, Z. Naturforsch.,
60b, 1105 (2005).
19. D. S. Bhuvaneshwari, K. P. Elango, Int. J. Chem. Kinet., 38, 657 (2006).
20. C. Karunakaran, P. N. Palanysamy, Int. J. Chem. Kinet., 31, 571 (1999).
21. A. Agarwala, V. Bagchi, D. Bandyopadhyay, J. Chem. Sci., 117, 187
(2005).
22. Xian-Tai Zhou, Hong-Bing Ji , Qiu-Lan Yuan, J. Porphyr. Phthalocya.,
12, 94 (2008).
17. Corwin Hansch, A. Leo, R. W. Taft, Chem. Rev., 91, 165 (1991).
18. C. Karunakaran, P. N. Palanysamy, Organic Reactivity, 31, 51 (1997).
23. Ik Hwan Um, Eun Ju Lee , Ji Sook Min, Tetrahedron., 57, 9585 (2001)
1360