Mechanistic aspects of uncatalyzed and ruthenium(III) catalyzed oxidation of DL-ornithine monohydrochloride by silver(III) periodate complex in aqueous alkaline medium

Article abstract of DOI:10.1016/j.ica.2010.03.081

The oxidation of an amino acid, DL-ornithine monohydrochloride (OMH) by diperiodatoargentate(III) (DPA) was carried out both in the absence and presence of ruthenium(III) catalyst in alkaline medium at 25°C and a constant ionic strength of 0.10 mol dm^-3 spectrophorometrically. The reaction was of first order in both catalyzed and uncatalyzed cases, with respect to [DPA] and was less than unit order in [OMH] and negative fraction in [alkali]. The order with respect to [OMH] changes from first order to zero order as the [OMH] increases. The order with respect to Ru(III) was unity. The uncatalyzed reaction in alkaline medium has been shown to proceed via a DPA-OMH complex, which decomposes in a rate determining step to give the products. Where as in catalyzed reaction, it has been shown to proceed via a Ru(III)-OMH complex, which further reacts with two molecules of DPA in a rate determining step to give the products. The reaction constants involved in the different steps of the mechanisms were calculated for both the reactions. The catalytic constant (K_cat.const.) was also calculated for catalyzed reaction at different temperatures. The activation parameters with respect to slow step of the mechanism and also the thermodynamic quantities were determined.

Full text of DOI:10.1016/j.ica.2010.03.081

Inorganica Chimica Acta 363 (2010) 2430–2442
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Mechanistic aspects of uncatalyzed and ruthenium(III) catalyzed oxidation of
DL-ornithine monohydrochloride by silver(III) periodate complex in aqueous
alkaline medium
Shweta J. Malode, Jyothi C. Abbar, Sharanappa T. Nandibewoor *
P.G. Department of Studies in Chemistry, Karnatak University, Dharwad 580 003, India
a r t i c l e i n f o
a b s t r a c t
Article history:
The oxidation of an amino acid, DL-ornithine monohydrochloride (OMH) by diperiodatoargentate(III)
Received 23 November 2009
Received in revised form 22 March 2010
Accepted 31 March 2010
(
DPA) was carried out both in the absence and presence of ruthenium(III) catalyst in alkaline medium
ꢀ3
at 25 °C and a constant ionic strength of 0.10 mol dm spectrophotometrically. The reaction was of first
order in both catalyzed and uncatalyzed cases, with respect to [DPA] and was less than unit order in
Available online 10 April 2010
[OMH] and negative fraction in [alkali]. The order with respect to [OMH] changes from first order to zero
order as the [OMH] increases. The order with respect to Ru(III) was unity. The uncatalyzed reaction in
alkaline medium has been shown to proceed via a DPA–OMH complex, which decomposes in a rate deter-
mining step to give the products. Where as in catalyzed reaction, it has been shown to proceed via a
Ru(III)–OMH complex, which further reacts with two molecules of DPA in a rate determining step to give
the products. The reaction constants involved in the different steps of the mechanisms were calculated
for both the reactions. The catalytic constant (KCat.const.) was also calculated for catalyzed reaction at dif-
ferent temperatures. The activation parameters with respect to slow step of the mechanism and also the
thermodynamic quantities were determined.
Keywords:
DL-Ornithine monohydrochloride
Diperiodatoargentate(III)
Ru(III) catalysis
Oxidation
Kinetics
Ó 2010 Elsevier B.V. All rights reserved.
1
. Introduction
Amino acids act not only as the building blocks in protein syn-
tion of various substrates. They normally found that order with re-
spect to both oxidant and substrate was unity and OH was found
to enhance the rate of reaction. It was also observed that they did
not arrive the possible active species of DPA in alkali and on the
ꢀ
theses but they also play a significant role in metabolism and have
been oxidized by a variety of oxidizing agents [1]. The study of the
oxidation of amino acids is of interest because of their biological
significance and selectivity towards the oxidant to yield the differ-
ent products [2]. Ornithine is one of the non-protein amino acids
which is derived from the break down of arginine during the citric
acid cycle. It is the most potent amino acid studied for stimulating
the production of release of growth hormone in the body from the
pituitary gland, which in turn helps with fat metabolism. It is fur-
ther required for a properly functioning immune system and liver
and assists in ammonia detoxification and liver rejuvenation. It is
also of use in healing and repairing skin and tissue. Ornithine has
the ability to regenerate the thymus gland, liver, and heart tissue,
enhance muscle growth, and increase immune system function [3].
Diperiodatoargentate(III) (DPA) is a powerful oxidizing agent in
alkaline medium with the reduction potential [4], 1.74 V. It is
widely used as a volumetric reagent for the determination of var-
ious organic and inorganic species [5,6]. Jayaprakash Rao et al.
other hand they proposed mechanisms by generalizing the DPA
as [Ag(HL)L](
x + 1)ꢀ
. However, Kumar et al. [9–11] put an effort to
give an evidence for the reactive form of DPA in the large scale of
alkaline pH. When the Ag(III) species are involved, it would be
interesting to know which of the species is the active oxidant. In
the present investigation, we have obtained the evidence for the
reactive species for the DPA in alkaline medium. The DPA is a metal
3
+
3+
complex with Ag in 3+ oxidation state like Cu in DPC and Fe in
hemoglobin.
Transition metals are known to catalyze many oxidation–reduc-
tion reactions since they involve multiple oxidation states. In re-
cent years, the use of transition metal ions such as osmium,
ruthenium, palladium, chromium and iridium either alone or as
binary mixtures, as catalysts in various redox processes has at-
tracted considerable interest [12]. The Ru(III) acts as a catalyst in
the oxidation of many organic and inorganic substrates [13,14].
The catalyzed mechanism can be quite complicated due to forma-
tion of different intermediate complexes, and different oxidation
states of ruthenium(III). Although the mechanism of catalysis de-
pends on the nature of the substrate, oxidant and on experimental
conditions, it has been shown [15] that metal ions act as catalysts
[
7,8] have used DPA as an oxidizing agent for the kinetics of oxida-
*
Corresponding author. Tel.: +91 836 2215286; fax: +91 836 2747884 (Off.).
E-mail address: stnandibewoor@yahoo.com (S.T. Nandibewoor).
0
020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.03.081

S.J. Malode et al. / Inorganica Chimica Acta 363 (2010) 2430–2442
2431
by one of these different paths such as the formation of complexes
to boiling and 20 g of K
S
2 2
O
8
was added in several lots with stirring
with reactants or oxidation of the substrate itself or through the
formation of free radicals. In earlier reports [16], it has been ob-
served that Ru(III) forms a complex with the substrate, which gets
oxidized by the oxidant to form Ru(IV)–substrate complex fol-
lowed by the rapid redox decomposition to regenerate Ru(III). In
another report [17], it has been observed that there involves the
formation of a Ru(III)–substrate complex with further cleavage in
a concerted manner giving rise to a Ru(I) species, which gets rap-
idly oxidized by the oxidant to regenerate the catalyst. In some
other reports [18], it is observed that Ru(III) forms a complex with
substrate and is oxidized by the oxidant with the regeneration of
the catalyst. Hence, understanding the role of Ru(III) in catalyzed
reaction is important. We have observed that, ruthenium(III) cata-
lyzes the oxidation of OMH by DPA in alkaline medium in micro
amounts.
and then allowed to cool. It was filtered through a medium poros-
ity fritted glass filter and 40 g of NaOH was added slowly to the fil-
trate, whereupon a voluminous orange precipitate agglomerates.
The precipitate is filtered and washed 3–4 times with cold water.
3
The pure crystals were dissolved in 50 cm water and warmed to
80 °C with constant stirring thereby some solid was dissolved to
give a red solution. The resulting solution was filtered when it
was hot and on cooling at room temperature, the orange crystals
separated out and were recrystallized from water.
The complex was characterized from its UV spectrum, which
exhibited three peaks at 216, 255 and 362 nm. These spectral fea-
tures were identical to those reported earlier for DPA [20]. The
magnetic moment study revealed that the complex is diamagnetic.
The compound prepared was analyzed [21] for silver and periodate
by acidifying a solution of the material with HCl, recovering and
weighing the AgCl for Ag and titrating the iodine liberated when
The literature survey reveals that there is no report on the
uncatalyzed and catalyzed oxidative mechanism of DL-ornithine
monohydrochloride [(±)-2,5-diaminopentanoic acid monohydro-
chloride] by diperiodatoargentate(III) in alkaline medium. Such
oxidation studies may throw some light on the mechanism of con-
versions of the compounds in biological systems. In earlier reports
ꢀ
excess of KI was added to the filtrate for IO4 . The stock solution
of DPA was used for the required [DPA] solution in the reaction
mixture.
2.3. Instruments used
ꢀ
of DPA oxidation [18], the order in [OH ] was found to be less than
unity and periodate had a retarding effect in most of the reactions
and monoperiodatoargentate(III) (MPA) was considered to be
active species. However, in the present study we have observed
entirely different kinetic observations and diperiodatoargen-
tate(III) (DPA) itself is found to be active form of oxidant. In order
to understand the active species of oxidant and catalyst, to com-
pute the activity of the catalyst and to propose the appropriate
mechanisms, the title reaction is investigated in detail. An under-
standing of the mechanism allows the chemistry to be interpreted,
understood and predicted.
(i) For kinetic measurements, a Peltier Accessory (temperature
control) attached to Varian CARY 50 Bio UV–Visible spectro-
photometer (Varian, Victoria-3170, Australia) connected to a
rapid kinetic accessory (HI-TECH SFA-12, UK) was used.
(ii) For product analysis, a QP-2010S Shimadzu gas chromato-
graph mass spectrometer, Nicolet 5700-FT-IR spectrometer
(Thermo, USA), 300 MHz H NMR spectrophotometer (Bru-
ker, Switzerland) were used.
(iii) For pH measurements ELICO pH meter model LI 120 was
used.
1
2.4. Kinetic measurements
2
. Experimental
Kinetic measurements were performed on a Varian CARY 50 Bio
2
.1. Materials and reagents
UV–Visible spectrophotometer. The kinetics was followed under
pseudo-first-order conditions where [OMH] > [DPA] in both uncat-
alyzed and catalyzed reactions at 25.0 ± 0.1 °C, unless otherwise
specified. In the absence of catalyst the reaction was initiated by
mixing the DPA to OMH solution, which also contained required
All reagents used were of analytical reagent grade and millipore
water was used throughout the work. A solution of DL-ornithine
monohydrochloride (HiMedia Laboratories) was prepared by dis-
solving an appropriate amount of recrystallized sample in milli-
pore water. The purity of DL-ornithine monohydrochloride sample
was checked by comparing its melting point, 232 °C with the liter-
ature data [literature melting point = 233 °C]. The required concen-
tration of OMH was obtained from its stock solution. A standard
concentrations of KNO
ence of Ru(III) catalyst was initiated by mixing the DPA to OMH
solution which also contained required concentrations of KNO
KOH, KIO and Ru(III) catalyst. Since the initial rate was too fast
3 4
, KIO and KOH. The reaction in the pres-
3
,
4
to be monitored by usual methods in the catalyzed reaction, the ki-
netic measurements were performed on a Hitachi 150-20 UV–Vis-
ible spectrophotometer attached to a rapid kinetic accessory (HI-
TECH SFA-12, UK). The progress of the reaction was followed spec-
trophotometrically at 360 nm by monitoring the decrease in absor-
stock solution of Ru(III) was prepared by dissolving RuCl
3
(S.D. Fine
Chem.) in 0.20 mol dm HCl. The concentration was determined
19] by EDTA titration.
A stock standard solution of IO4 was prepared by dissolving a
known weight of KIO (S.D. Fine Chem.) in hot water and used after
ꢀ3
[
ꢀ
4
bance due to DPA with the molar absorbancy index, ‘
3900 ± 100 dm mol cm in both catalyzed and uncatalyzed
e
’ to be
keeping for 24 h to complete the equilibrium. Its concentration
was ascertained iodometrically [20] at neutral pH maintained
using phosphate buffer. The pH of the medium in the solution
3
ꢀ1
ꢀ1
1
reaction. It was verified that there is a negligible interference from
other species present in the reaction mixture at this wavelength.
The reaction was followed to more than 90% completion of the
reaction. Plots of log(absorbance) versus time lead to the first-order
was measured by ELICO (LI 120) pH meter. KNO
BDH) were used to maintain ionic strength and alkalinity of the
reaction, respectively. Aqueous solution of AgNO was used to
3
(AR) and KOH
(
3
rate constants (‘k
tion of reaction. The orders for various species were determined
from the slopes of plots of log(k or k ) versus respective concen-
tration of species except for [DPA] in which non-variation of ‘k
and k ’ was observed as expected to the reaction condition. The
rate constants were reproducible within ±5%. During the kinetics,
U C
or k ’). The plots were linear up to 85% comple-
study the product effect, Ag(I). t-Butyl alcohol (S.D. Fine Chem.)
was used to study the dielectric constant of the reaction medium.
U
C
U
2.2. Preparation of DPA
C
ꢀ
5
ꢀ3
DPA was prepared by oxidizing Ag(I) in the presence of KIO
4
as
a constant concentration viz. 5.0 ꢁ 10 mol dm
4
of KIO was
described elsewhere [21]. The mixture of 28 g of KOH and 23 g of
KIO in 100 cm of water along with 8.5 g AgNO was heated just
4 3
used throughout the study unless otherwise stated. Thus, the pos-
sibility of oxidation of DL-ornithine monohydrochloride by perio-
3

2
432
S.J. Malode et al. / Inorganica Chimica Acta 363 (2010) 2430–2442
date was tested and found that there was no significant interfer-
ence due to KIO under both the experimental conditions. The total
concentration of OH and IO4 was calculated by considering the
amount present in the DPA solution and that additionally added.
In view of the modest concentration of alkali used in the reac-
tion medium, attention was also directed to the effect of the reac-
tion vessel surface on the kinetics. Use of polythene/acrylic wares
and quartz or polyacrylate cells gave the same results, indicating
that the surface did not have any significant effect on the reaction
rates.
Regression analysis of experimental data to obtain regression
coefficient ‘r’ and the standard deviation ‘S’, of points from the
regression line, was performed with the Microsoft office Excel-
2003 program.
4
ꢀ
ꢀ
Kinetics runs were also carried out in N
understand the effect of dissolved oxygen on the rate of reaction.
No significant difference in the results was obtained under a N
2
atmosphere in order to
2
atmosphere and in the presence of air. In view of the ubiquitous
contamination of carbonate in the basic medium, the effect of car-
bonate was also studied. Added carbonate had no effect on the
reaction rates. The spectral changes during the chemical reaction
for the standard condition at 25 °C are shown in Fig. 1 (for uncat-
alyzed). It is evident from the figure that the concentration of
DPA decreases at 360 nm.
3
. Results
3.1. Stoichiometry and product analysis
Different sets of reaction mixtures containing varying ratios of
ꢀ
DPA to OMH in the presence of constant amount of OH and
3
KNO in uncatalyzed reaction and a constant amount of Ru(III) in
catalyzed reaction were kept for 2 h in a closed vessel under nitro-
gen atmosphere. The remaining concentration of DPA was esti-
mated spectrophotometrically at 360 nm. The results indicated
1
:2 stoichiometry (OMH:DPA) for both the reactions as given in
Scheme 1.
The stoichiometric ratio in both the cases suggests the main
product as 4-aminobutyric acid. The product was extracted with
ether and recrystallized from aqueous alcohol. It was characterized
1
by FT-IR, GC–MS, and H NMR spectral studies.
The presence of carboxylic acid was confirmed by IR spectros-
copy [22] which showed ˜C@O stretching of carboxylic acid at
ꢀ
1
1
708 cm
indicating the presence of acidic C@O group, O–H
ꢀ1
stretching of carboxylic acid at 2848 cm indicating the presence
ꢀ1
of acidic –OH group and N–H stretching at 3427 cm indicating
the presence of –NH group in the product. 4-aminobutyric acid
was further characterized by H NMR spectrum (CDCl
Fig. 1. Spectroscopic changes occurring in the oxidation of DL-ornithine monohy-
drochloride by alkaline DPA at 25 °C, [DPA]=5.0 ꢁ 10 5, [OMH] = 5.0 ꢁ 10
ꢀ
ꢀ4
,
2
ꢀ
ꢀ
ꢀ5
ꢀ3
1
[
OH ] = 0.08, ½IO ꢂ ¼ 5:0 ꢁ 10 and I = 0.10 mol dm with scanning time of: (1)
4
3
) two triplet
1
.0, (2) 2.0, (3) 3.0, (4) 4.0, (5) 5.0 and (6) 6.0 min.
2
at 2.31 d (a) and 2.69 d (c) and multiplet at 1.84 d (due to (b) CH ),
c
b
Ru(III)
NH2
COO-
[Ag(H IO ) ]
-
+3[OH-]
NH
2
+ 2
3
6
2
a
2-
+
NH
+ 2Ag(I) + 4H
IO
+ CO
3
3
6
2
COOH
+
H O
2
NH2
Scheme 1. Stoichiometry of uncatalyzed and ruthenium(III) catalyzed oxidation of DL-ornithine monohydrochloride by alkaline diperiodatoargentate(III).
Fig. 2. GC–mass spectrum of 4-aminobutyric acid with its molecular ion peak at 103 m/z.

S.J. Malode et al. / Inorganica Chimica Acta 363 (2010) 2430–2442
2433
5
.44 d (s, 2H due to –NH
2
) and 11.6 d (s, H due to –COOH), –NH
O. Further, the product was
2
formation of AgCl. It was observed that 4-aminobutyric acid does
not undergo further oxidation under the present kinetic conditions.
and –OH were vanished on adding D
2
subjected to GC–MS spectral analysis. GC–MS data was obtained
on a QP-2010S Shimadzu gas chromatograph mass spectrometer.
The mass spectrum showed a molecular ion peak at 103 amu con-
firming 4-aminobutyric acid product (Fig. 2). All other peaks ob-
served in GC–MS can be interpreted in accordance with the
observed structure of the 4-aminobutyric acid.
3.2. Reaction orders
As the diperiodatoargentate(III) oxidation of DL-ornithine mono-
hydrochloride in alkaline medium proceeds with a measurable rate
in the absence of Ru(III), the catalyzed reaction is understood to oc-
cur in parallel paths with contributions from both the catalyzed
The by-products were identified as ammonia by Nessler’s re-
agent [23] and the CO was qualitatively detected by bubbling
2
nitrogen gas through the acidified reaction mixture and passing
the liberated gas through the tube containing limewater. The for-
mation of free Ag in solution was detected by adding KCl solution
and uncatalyzed paths. Thus, the total rate constant (k
to the sum of the rate constants of the catalyzed (k ) and uncata-
lyzed (k ) reactions, so k = k . Hence the reaction orders have
ꢀ k
been determined from the slopes of logk versus log(concentration)
T
) is equal
C
+
U
C
T
U
to the reaction mixture, which produced white turbidity due to the
C
Table 1
Effect of variation of [DPA], [OMH], [OH ] and ½IO ꢀꢂ on the oxidation of DL-ornithine monohydrochloride by diperiodatoargentate(III) in aqueous alkaline medium at 25 °C and
ꢀ
4
ꢀ
3
I = 0.10 mol dm
.
5
ꢀ3
4
ꢀ3
ꢀ
1
ꢀ3
IO4ꢀꢂ ꢁ 105 ðmol dmꢀ3Þ
3
ꢀ1
[
DPA] ꢁ 10 (mol dm
)
[OMH] ꢁ 10 (mol dm
)
[OH ] ꢁ 10 (mol dm
)
k
U
ꢁ 10 (s
)
½
Found
Calculated
2.21
1
3
5
7
.0
.0
.0
.0
5.0
5.0
5.0
5.0
5.0
0.7
1.0
3.0
5.0
7.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.1
0.2
0.4
0.8
1.0
0.8
0.8
0.8
0.8
0.8
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
1.0
3.0
5.0
7.0
2.04
1.97
2.19
2.23
2.16
0.41
0.57
1.49
2.19
2.57
4.11
3.58
2.82
2.19
1.99
2.25
1.94
2.19
2.22
2.12
2.21
2.21
2.21
2.21
0.43
0.59
1.52
2.21
2.74
3.95
3.55
2.95
2.21
1.96
2.21
2.21
2.21
2.21
2.21
1
0.0
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
10.0
Table 2
Effect of variation of [DPA], [OMH], [OH ], [IO4 ] and [Ru(III)] on the ruthenium(III) catalyzed oxidation of DL-ornithine monohydrochloride by diperiodatoargentate(III) in
ꢀ
ꢀ
ꢀ
3
aqueous alkaline medium at 25 °C and I = 0.10 mol dm
.
5
4
ꢀ
1
IO4ꢀꢂ ꢁ 105 ðmol dmꢀ3Þ
6
2
3
2
ꢀ1
[
(
DPA] ꢁ 10
[OMH] ꢁ 10
[OH ] ꢁ 10
[Ru(III)] ꢁ 10
k
(s
T
ꢁ 10
k
U
ꢁ 10
k
C
ꢁ 10 (s
)
½
ꢀ
3
ꢀ3
ꢀ3
ꢀ3
ꢀ1
ꢀ1
mol dm
)
(mol dm
)
(mol dm
)
(mol dm
)
)
(s )
Found
Calculated
1.43
1
3
5
7
.0
.0
.0
.0
5.0
5.0
5.0
5.0
5.0
0.7
1.0
3.0
5.0
7.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.1
0.2
0.4
0.8
1.0
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
1.0
3.0
5.0
7.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
1.0
3.0
5.0
8.0
10.0
1.57
1.52
1.65
1.83
1.71
0.32
0.43
1.15
1.65
2.11
4.22
3.41
2.43
1.65
1.43
1.71
1.53
1.65
1.67
1.55
0.67
1.65
2.60
4.01
5.02
2.04
1.97
2.19
2.23
2.16
0.41
0.57
1.49
2.19
2.57
4.11
3.58
2.82
2.19
1.99
2.25
1.94
2.19
2.22
2.12
2.19
2.19
2.19
2.19
2.19
1.37
1.32
1.43
1.60
1.49
0.28
0.37
1.00
1.43
1.85
3.81
3.05
2.14
1.43
1.23
1.49
1.33
1.43
1.45
1.34
0.45
1.43
2.38
3.78
4.80
1.43
1.43
1.43
1.43
0.28
0.39
0.99
1.43
1.77
3.70
3.01
2.20
1.43
1.22
1.43
1.43
1.43
1.43
1.43
0.47
1.43
2.38
3.82
4.77
1
0.0
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
10.0
5.0
5.0
5.0
5.0
5.0

2
434
S.J. Malode et al. / Inorganica Chimica Acta 363 (2010) 2430–2442
ꢀ
ꢀ
plots by varying the concentrations of OMH, IO4 , OH and catalyst
Ru(III), in turn while keeping others constant.
[OMH] and k
C
versus [OMH] (Fig. 3). (r P 0.994, S 6 0.003 for
uncatalyzed, r P 0.997, S 6 0.024 for Ru(III) catalyzed). However,
the order with respect to [OMH] changes from first order to zero
order as the [OMH] increases.
3.3. Effect of [diperiodatoargentate(III)]
In the absence and in the presence of Ru(III) catalyst, the DPA
3.5. Effect of [Ru(III)]
ꢀ5
ꢀ4
concentration was varied in the range of 1.0 ꢁ 10 –1.0 ꢁ 10
ꢀ3
ꢀ6
mol dm and the linearity of the plots of log(absorbance) versus
time up to 85% completion of the reaction indicates a reaction or-
der of unity in [DPA] (r P 0.918, S 6 0.014). This is also confirmed
by varying of [DPA], which did not result in any change in the pseu-
The ruthenium(III) concentration was varied from 1.0 ꢁ 10 to
ꢀ5
ꢀ3
1.0 ꢁ 10 mol dm
range, at constant concentrations of DPA,
OMH, alkali and ionic strength. The order in [Ru(III)] was found
to be unity from the linearity of the plot of kC versus [Ru(III)]
(r P 0.999, S 6 0.023) (Table 2 Ru(III) catalyzed).
U C
do-first-order rate constants, k (Table 1 uncatalyzed), k (Table 2
Ru(III) catalyzed).
3.6. Effect of [alkali] and [periodate]
3.4. Effect of [DL-ornithine monohydrochloride]
The effect of alkali in the absence and presence of Ru(III) cata-
ꢀ
3
In both the cases the DL-ornithine monohydrochloride concen-
lyst reaction was studied in the range of 0.01–0.10 mol dm at
ꢀ5
ꢀ4
ꢀ3
ꢀ
tration was varied in the range of 7.0 ꢁ 10 –7.0 ꢁ 10 mol dm
at 25 °C while keeping other reactant concentrations and condi-
tions constant. The k and k values increased with the increase
constant concentrations of OMH, DPA, IO and ionic strength of
4
ꢀ3
0.10 mol dm . The rate constants decreased with increase in [al-
kali] and the order was found to be negative fraction, i.e., ꢀ0.32
in uncatalyzed and ꢀ0.48 in Ru(III) catalyzed reaction, which is
rarely observed in DPA oxidation (r P 0.987, S 6 0.004 for uncata-
lyzed, r P 0.987, S 6 0.027 for catalyzed) (Tables 1 and 2).
U
C
in concentration of OMH indicating an apparent less than unit or-
der dependence on [OMH] under the conditions of experiment (Ta-
ble 1 uncatalyzed and Table 2 Ru(III) catalyzed). This was also
.81
confirmed by the plots of k
U
versus [OMH]0
and k
C
versus
versus
The periodate concentration was varied in the range of
.82
ꢀ5
ꢀ4
[
OMH]0 which were linear rather than the direct plot of k
U
1.0 ꢁ 10 –1.0 ꢁ 10
at constant concentrations of DPA, OMH,
ꢀ
OH and ionic strength in uncatalyzed and with constant concen-
tration Ru(III) in catalyzed reaction. It was observed that the added
periodate had no effect on the reaction (Tables 1 and 2), which is
also an unusual case in DPA oxidation.
0.81
3
-3
A
[OMH]
6.0
x 10 (mol dm )
4.0
10.0
8.0
2.0
0.0
Thus, from the observed experimental results:
The rate law for uncatalyzed reaction is given as:
3
2
1
0
.0
0.0
1.0
2.0
3.0
1:0
Rate ¼ k
U
½DPAꢂ ½OMHꢂ0:81½OHꢀꢂꢀ0:32
.0
.0
.0
The rate law for Ru(III) catalyzed reaction is given as:
1:0
Rate ¼ k
C
½DPAꢂ ½OMHꢂ0:82½OHꢀꢂꢀ0:48½RuðIIIÞꢂ1:0
3
.7. Effect of ionic strength (I) and dielectric constant of the medium
(D)
k
k
The effect of varying [KNO
3
] at constant [DPA], [Ru(III)], [OMH],
ꢀ
ꢀ
[
OH ] and IO was found that increasing ionic strength had no
4
significant effect on the rate of the reaction in both the cases of
uncatalyzed and catalyzed reactions.
Varying the t-butyl alcohol and water percentage varied dielec-
tric constant of the medium, ‘D’. The D values were calculated from
0
.0
1.0
2.0
4
3.0
4.0
0.0
-3
[
OMH] x 10 (mol dm )
the equation D = D
stants of pure water and t-butyl alcohol, respectively, and V
are the volume fractions of components water and t-butyl alco-
V
w w
+ D
B
V
B
, where D
w
and D
B
are dielectric con-
0
.82
3
-3
[OMH]
x 10 (mol dm
)
B
and
w
4.0
3.0
2.0
1.0
V
B
2
1
1
0
0
.0
.5
.0
.5
.0
0.0
hol, respectively, in the total mixture. It was observed that there
was no effect of dielectric constant on the rate of uncatalyzed reac-
tion but in case of Ru(III) catalyzed reaction the rate constant k
C
de-
0
.5
.0
.5
.0
creased with decrease in dielectric constant of the reaction
medium and the plot of log k versus 1/D was linear with negative
C
slope.
1
1
2
3
.8. Effect of initially added products
k
k
In both the cases initially added products, Ag(I), and 4-amino-
butyric acid did not have any significant effect on the rate of
reaction.
2.5
10 .0
0
.0
2.0
4.0
6.0
8.0
3.9. Test for free radicals (polymerization study)
4
-3
[
OMH] x 10 (mol dm )
vs [OMH]0.81 and k
vs [OMH] (conditions as in Table 2).
To test the intervention of free radicals for both uncatalyzed and
catalyzed reactions, the reaction mixture was mixed with acryloni-
Fig. 3. Plots of (A) k
U
U C
vs [OMH] (conditions as in Table 1) (B) k
0
.82
vs [OMH]
and k
C

S.J. Malode et al. / Inorganica Chimica Acta 363 (2010) 2430–2442
2435
trile monomer and kept for 2 and 1 h, respectively, under nitrogen
3.11. Catalytic activity
atmosphere. On dilution with methanol, a white precipitate was
formed, indicating the intervention of free radicals in the reactions.
The blank experiments of either DPA or DL-ornithine alone with
acrylonitrile did not induce any polymerization under the same
condition as those induced for the reaction mixture. Initially added
acrylonitrile decreases the rate of reaction indicating free radical
intervention, which is the case in earlier work [24].
It has been pointed out by Moelwyn-Hughes [25] that in the
presence of the catalyst, the uncatalyzed and catalyzed reactions
proceed simultaneously, so that
x
k
T
¼ k
U
þ KCat:const½Catalystꢂ
ð1Þ
Here ‘k
presence Ru(III) catalyst, ‘k
for the uncatalyzed reaction, ‘KCat.const.’ the catalytic constant and
x’ the order of the reaction with respect to [Ru(III)]. In the present
investigations, x values for the standard run was found to be unity.
Then the value of KCat.const. is calculated using the equation,
T
’ is the observed pseudo-first-order rate constant in the
3
.10. Effect of temperature (T)
U
’ the pseudo-first-order rate constant
The influence of temperature on the rate of reaction was studied
‘
for both uncatalyzed and catalyzed reaction at six different tem-
peratures (15, 20, 25, 30, 35 and 40 °C) under varying concentra-
tions of DL-ornithine monohydrochloride and alkali keeping other
conditions constant. The rate constant was found to increase with
increase in temperature. The rate constant (k
the uncatalyzed reaction mechanism was obtained from the slopes
1
) of the slow step of
Table 4
Activation parameters and thermodynamic quantities for the ruthenium(III) catalyzed
oxidation of DL-ornithine monohydrochloride by diperiodatoargentate(III) in aqueous
alkaline medium with respect to the slow step of Scheme 3: (A) effect of temperature,
and intercepts of plots of 1/k
U U
versus 1/[OMH] and 1/k versus
ꢀ
[
OH ] plots at six different temperatures and were used to calcu-
(
B) activation parameters (Scheme 3), (C) effect of temperature to calculate K
for the Ru(III) catalyzed oxidation of DL-ornithine monohydrochloride by diperiodat-
oargentate(III) in alkaline medium, (D) thermodynamic quantities using K and K
3 4
and K
late the activation parameters. The energy of activation corre-
sponding to these constants was evaluated from the Arrhenius
3
4
.
plot of logk
parameters obtained are tabulated in Table 3.
Similarly the rate constant (k ) of the slow step of catalyzed
reaction mechanism was obtained from the slopes and the inter-
1
versus 1/T (r P 0.988, S 6 0.012) and other activation
ꢁ 10ꢀ5 (dm3 mol
ꢀ1 ꢀ1
(
A) Temperature (K)
k
2
s )
2
2
2
303
3
3
88
93
98
0.25
0.34
0.48
0.67
0.87
1.58
2
cept of the plots of [Ru(III)]/k
sus [OH ] at six different temperatures. The values are given in
C
versus 1/[OMH] and [Ru(III)]/k
C
ver-
ꢀ
08
13
Table 4. The energy of activation for the rate determining step
was obtained by the least square method of plot of logk versus
2
(
B) Parameters
Values
E
a
(k J molꢀ1)
52.1
49.6
11.3
46.2
13.8
1
/T (r P 0.978, S 6 0.022) and other activation parameters calcu-
#
ꢀ1
D
D
D
H
(k J mol
)
lated for the reaction are presented in Table 4.
#
ꢀ1
ꢀ1
S
(J K mol
)
#
ꢀ1
Table 3
G
(k J mol )
Activation parameters and thermodynamic quantities for the oxidation of OMH by
diperiodatoargentate(III) in aqueous alkaline medium with respect to the slow step of
Scheme 2: (A) effect of temperature, (B) activation parameters (Scheme 2), (C) effect
logA
1
ꢀ3
(
C) Temperature (K)
K
(
3
ꢁ 10
K
4
ꢁ 10
ꢀ3
3
ꢀ1
mol dm
)
(dm mol )
of temperature to calculate K
chloride by diperiodatoargentate(III) in aqueous alkaline medium, (D) thermody-
namic quantities using K and K
1 2
and K for the oxidation of DL-ornithine monohydro-
288
293
2
303
3
3
0.79
0.53
0.34
0.29
0.25
0.20
0.53
0.75
0.98
1.19
1.44
1.50
1
2
.
98
2
ꢀ1
(
A) Temperature (K)
k
1
ꢁ 10 (s
)
08
13
2
2
2
3
3
3
88
93
98
03
08
13
0.38
0.52
0.68
0.94
1.38
2.08
(D) Thermodynamic
quantities
Values from K3
Values from K4
ꢀ
1
D
D
D
H (k J mol
)
ꢀ39.7
ꢀ162
8.3
31.5
163
ꢀ
1
ꢀ1
S (J K mol
)
(
B) Parameters
Values
G298 (k J molꢀ1
)
ꢀ17.1
ꢀ4
ꢀ
½IO4ꢀꢂ ¼ 5:0 ꢁ 10ꢀ5
[
[
DPA] = 5.0 ꢁ 10ꢀ5,
[OMH] = 5.0 ꢁ 10
,
[OH ] = 0.08,
,
E
a
(k J molꢀ1)
49.7
47.2
ꢀ127
85
ꢀ6
ꢀ3
Ru(III)] = 3.0 ꢁ 10 , I = 0.10 mol dm
.
#
ꢀ1
D
D
D
H
(k J mol
)
#
ꢀ1
ꢀ1
S
(J K mol
)
#
ꢀ1
G
(k J mol )
Table 5
Values of catalytic constant (KCat.const
parameters calculated using KCat.const values.
logA
6.5
)
at different temperatures and activation
1
ꢀ4
(
C) Temperature (K)
K
(
1
ꢁ 10
K
2
ꢁ 10
3
mol dmꢀ3)
(dm mol
ꢀ1
)
ꢁ 10ꢀ
4
Temperature (K)
K
C
2
2
2
3
3
3
88
93
98
03
08
13
0.54
0.37
0.27
0.19
0.11
0.08
0.20
0.31
0.37
0.49
0.62
0.86
288
293
298
303
308
3
E
D
D
D
0.86
1.29
1.70
2.63
3.51
5.27
53.3
50.8
6.96
13
(
D) Thermodynamic
quantities
Values from K
1
Values from K
2
(k J molꢀ1)
a
#
ꢀ1
H
(k J mol
)
ꢀ
1
#
ꢀ1
ꢀ1
D
D
D
H (k J mol
)
ꢀ57
ꢀ222
8.9
41
205
ꢀ20
S
(J K mol
)
ꢀ
1
ꢀ1
#
ꢀ1
S (J K mol
298 (k J mol
)
)
G
(k J mol
)
48.8
13.5
ꢀ
1
G
logA
[
DPA] = 5.0 ꢁ 10 5,
ꢀ
[OMH] = 5.0 ꢁ 10ꢀ4
,
[OH ] = 0.08,
ꢀ
½IO4ꢀꢂ ¼ 5:0 ꢁ 10ꢀ5
,
ꢀ5
ꢀ4
ꢀ
½IO4ꢀꢂ ¼ 5:0 ꢁ 10ꢀ5
[DPA] = 5.0 ꢁ 10
,
[OMH] = 5.0 ꢁ 10
,
[OH ] = 0.08,
,
I = 0.10 mol dm 3.
ꢀ
ꢀ6
ꢀ3
[
Ru(III)] = 3.0 ꢁ 10 , I = 0.10 mol dm
.

2
436
S.J. Malode et al. / Inorganica Chimica Acta 363 (2010) 2430–2442
k
T
ꢀ k
Catalystꢂ
The values of KCat.const. were evaluated at different temperatures
U
k
C
(OMH:DPA) with a first order dependence on [DPA] and an appar-
ent order of less than unit order in [substrate], a negative fractional
order dependence on [alkali]. No effect of added products was ob-
served. Based on the experimental results, a mechanism is pro-
posed for which all the observed orders in each constituent such
K
Cat:const
¼
¼
ðwhere k
T
ꢀ k
U
¼ k
C
Þ
ð2Þ
x
x
½
½Catalystꢂ
and found to vary at different temperatures. Further, plots of logK-
Cat.const. versus 1/T were linear and the values of energy of activation
and other activation parameters with reference to catalyst were
computed and the results are summarized in Table 5. The value
ꢀ
ꢀ
as [DPA], [OMH], [OH ] and [IO ] may be well accommodated.
4
It is interesting to note that in most of the reports [18] on DPA
ꢀ
oxidation, OH had an increasing effect on the rate of the reaction,
4
of KCat.const. at 25 °C is 1.7 ꢁ 10 .
periodate retarded the rate of reaction and MPA was considered as
active species of DPA. However, in the present kinetic study, differ-
ent kinetic results have been obtained. In this study, increasing the
4
. Discussion
ꢀ
concentration of OH decreases the rate of the reaction and negli-
In the later period of 20th century the kinetics of oxidation of
some organic and inorganic substrates have been studied by Ag(III)
species which may be due to its strong versatile nature of two elec-
gible effect of periodate on rate of reaction and DPA itself was the
active species of the reaction. The result of decrease in rate of reac-
tion with increase in alkalinity (Table 1) can be explained in terms
ꢀ
trons oxidant. Among the various species of Ag(III), AgðOHÞ4 , dipe-
ꢀ
of prevailing equilibrium of formation of [Ag(H IO ) ] from
3
6 2
riodatoargentate(III) and ethylenebis (biguanide), (EBS), silver(III) are
of maximum attention to the researchers due to their relative stabil-
2ꢀ
[
2
Ag(H IO
6
)(H
3 6
IO )] hydrolysis as given in the following equation:
K
1
ꢀ
Þꢂ2ꢀ þ H
Þ ꢂ þ ½OHꢀꢂ
ꢀ
ity [26]. The stability of AgðOHÞ4 is very sensitive towards traces of
½AgðH
2
IO
6
ÞðH
3
IO
6
2
O ꢀ ½AgðH
3
IO
6
ð6Þ
2
dissolved oxygen and other impurities in the reaction medium
whereupon it had not drawn much attention. However, the other
two forms of Ag(III) [27] are considerably stable; the DPA is used
in highly alkaline medium and EBS is used in highly acidic medium.
The literature survey [21] reveals that the water soluble dipe-
Such type of equilibrium (6) has been well noticed in the liter-
ature [31]. Because of this reaction and fact that k values are in-
U
verse function of hydroxyl ion concentration with fractional
ꢀ
order in OH concentration, the main oxidant species is likely to
ꢀ
7ꢀ
2
be [Ag(H IO ) ] and its formation by the above equilibrium is
3
6 2
riodatoargentate(III) (DPA) has a formula [Ag(IO
6
)
2
]
with dsp
important in the present study. The less than unit order in
OMH] presumably results from formation of a complex (C ) be-
configuration of square planar structure, similar to diperiodatocop-
per(III) complex with two bidentate ligands, periodate to form a
planar molecule. When the same molecule is used in alkaline med-
ium, it is unlikely to exist as [Ag(IO
be in various protonated forms [28] depending on pH of the solu-
tion as given in following multiple equilibria Eqs. (3)–(5).
[
1
tween the DPA species and DL-ornithine monohydrochloride prior
7ꢀ
to the formation of the products. This complex (C ) decomposes
1
6
)
2
]
as periodate is known to
in a slow step to form a free radical derived from OMH. This free
radical species further reacts with Ag(II) in a fast step to form 4-
aminobutyraldehyde intermediate. This intermediate reacts with
one more mole of DPA species in a further fast step to form prod-
ucts such as 4-aminobutyric acid, Ag(I) and periodate as given in
Scheme 2.
ꢀ
þ
H
H
H
5
4
3
IO
6
ꢀ H
4
IO6 þ H
ð3Þ
ð4Þ
ð5Þ
ꢀ
IO6 þ Hþ
2ꢀ
IO6 ꢀ H
3
IO 2 ꢀ H
ꢀ
3ꢀ
þ
IO6 þ H
6
2
The direct plot of k
allel reaction if any along with interaction of oxidant and reduc-
tant. However the plot of k versus [OMH] was not linear. Thus,
U
versus [OMH] was drawn to know the par-
ꢀ
Periodic acid exists as H
pH 7. Hence, under alkaline conditions as employed in this study,
the main species are expected to be H
concentrations, periodate also tends to dimerise [4]. However, for-
mation of this species is negligible under conditions employed for
5 6 4
IO in acid medium and as H IO6 near
U
2
ꢀ
3ꢀ
IO6 and H
2
IO6 . At higher
in Scheme 2, the parallel reaction and involvement of two mole-
cules of OMH in the complex are excluded. The probable structure
3
1
of the complex (C ) is given as,
kinetic study. On contrary, the authors [7,8] in their recent studies
xꢀ
have proposed the DPA species as [Ag(HL)
2
]
in which ‘L’ is a per-
2
iodate with uncertain number of protons and ‘HL’ is a protonated
periodate of uncertain number of protons. This can be ruled out
by considering the alternative form [28] of IO at pH > 7 which
IO6 . Hence, DPA could be as
in alkaline medium. Therefore, un-
der the present condition, diperiodatoargentate(III), may be de-
OH
O
O
O
ꢀ
4
HO
I
OH
2
ꢀ
3ꢀ
is in the form H
3
IO6
or H
2
ꢀ
3ꢀ
[
3
Ag(H IO
6
)
2
]
or [Ag(H
2
IO
6
)
2
]
O
C
ꢀ
NH2
picted as [Ag(H
3
IO
6
)
2
] . The similar speciation of periodate in
O
Ag
alkali was proposed [29] for diperiodatonickelate(IV).
It is known that DL-ornithine exists in the form of zwitterion in
aqueous medium. In highly acidic medium it exists in the proton-
ated form, where as in highly basic medium it is in the deproto-
nated form [30].
O
O
NH2
HO
I
OH
OH
O
NH2
COO-
Spectroscopic evidence for the complex formation between oxi-
dant and substrate was obtained from UV–Vis spectra of DL-orni-
NH2
ꢀ4
ꢀ5
thine monohydrochloride (5.0 ꢁ 10 ), DPA ((5.0 ꢁ 10 ),
ꢀ
ꢀ3
4
.1. Mechanism for uncatalyzed reaction
[OH ] = 0.08 mol dm ) and mixture of both. A bathochromic shift
of 8 nm from 216 to 224 nm in the spectra of DPA to mixture of
DPA and OMH was observed (Fig. 4). The Michaelis–Menten plot
proved the complex formation between DPA and OMH, which ex-
The reaction between diperiodatoargentate(III) and DL-ornithine
monohydrochloride in alkaline medium has the stoichiometry 1:2

S.J. Malode et al. / Inorganica Chimica Acta 363 (2010) 2430–2442
2437
K1
2-
-
-
[
Ag(H IO )(H IO )] + H O
[Ag(H IO ) ] + [OH ]
3 6 2
2
6
3
6
2
K2
NH2
COO-
-
[
Ag(H IO ) ]
Complex (C1)
+
3
6 2
NH2
k1
NH2
2-
Complex(C1)
+ Ag(II) + CO + 2H IO
6
2
3
.
slow
NH2
fast
NH2
NH2
+ Ag(II)
+
NH + Ag(I)
3
.
OH-
CHO
NH2
fast
NH2
2-
NH2
-
3
+ Ag(I) + 2H IO6 + H O
2
+ [Ag(H IO ) ]
3
6 2
2
OH-
COOH
CHO
Scheme 2. Detailed Scheme for the oxidation of DL-ornithine monohydrochloride by alkaline diperiodatoargentate(III).
8
6
4
2
0
.0
.0
.0
.0
.0
A
2
88 K
93 K
2
k
2
98 K
303 K
3
3
08 K
13 K
0
.0
0.4
0.8
1.2
1.6
-
4
3
-1
1
/[OMH] x 10 (dm mol )
1.5
B
Fig. 4. Spectroscopic evidence for the complex formation between DPA and OMH
a) UV–vis spectra of DPA complex (362, 255 and 216 nm); (b) UV–vis spectra of
mixture of DPA and OMH (224 nm); and (c) UV–vis spectra of OMH.
(
1.2
0.9
0.6
0.3
288 K
plains the less than unit order dependence on [OMH]. Such com-
plex between an oxidant and substrate has also been observed in
other studies [18]. Scheme 2 leads to the rate law (7)
293 K
k
2
98 K
03 K
ꢀ
d½DPAꢂ
k
1
K
1
K
2
½OMHꢂ½DPAꢂ
þ K ½OMHꢂ
½OMHꢂ
þ K ½OMHꢂ
3
rate ¼
¼
ð7Þ
ð8Þ
ꢀ
308 K
dt
½OH ꢂ þ K
1
1 2
K
313 K
rate
1 1 2
k K K
k
U
¼
¼
ꢀ
½
DPAꢂ ½OH ꢂ þ K
1
1 2
K
0.0
0
.0
0.3
0.6
0.9
1.2
This explains all the observed kinetic orders of different species. The
rate law (8) can be rearranged into the following form, which is
suitable for verification
-
-3
[
OH ] x 10 (mol dm )
Fig. 5. Verification of rate law 9 for the oxidation of DL-ornithine monohydrochlo-
ride by diperiodatoargentate(III), Plots of (A) 1/k
six different temperatures (conditions as given in Table 1).
ꢀ
ꢀ
U
vs 1/[OMH], (B) 1/k
U
vs [OH ], at
1
½OH ꢂ
1
1
¼ k
þ k
þ k
1
ð9Þ
k
U
1
K
1
K
2
½OMHꢂ
1
K
2
½OMHꢂ
According to Eq. (9), other conditions being constant, plots of 1/
(r P 0.999, S 6 0.014) should be linear and are found to be so
(Fig. 5). The slopes and intercepts of such plots lead to the values
ꢀ
k
U
versus [OH ] (r P 0.991, S 6 0.012) and 1/k
U
versus 1/[OMH]

2
438
S.J. Malode et al. / Inorganica Chimica Acta 363 (2010) 2430–2442
as (2.70 ± 0.05) ꢁ 10 mol dmꢀ3, (3.7 ± 0.1) ꢁ 103
ꢀ
2
results, a mechanism is proposed for which all the observed orders
of K
1
, K
2
and k
1
3
ꢀ1
ꢀ3 ꢀ1
ꢀ
dm mol and (6.8 ± 0.2) ꢁ 10
s
, respectively.
in each constituent such as [DPA], [OMH], [Ru(III)], [OH ] and
ꢀ
The negligible effect of ionic strength and dielectric constant of
[IO4 ] may be well accommodated.
medium on the rate might be due to the presence of various ions
In the prior equilibrium step 1, the hydroxyl ion concentration
#
ꢀ
shown in Scheme 2. A high negative value of
J K mol ) suggests that intermediate complex (C
dered than the reactants [33].
D
S
(ꢀ127.5
with fractional order in OH concentration, the main oxidant spe-
ꢀ1
ꢀ1
ꢀ
1
) is more or-
cies is likely to be [Ag(H
3
IO
6
)
2
]
and its formation by the above
equilibrium is important in the present study. The less than unit
order in [OMH] presumably results from formation of a complex
The thermodynamic quantities for the first and second equilib-
rium steps of Scheme 2 can be evaluated as follows. [OMH] and
(C
2
) between the Ru(III) species and DL-ornithine monohydrochlo-
) reacts with one mole of DPA in a slow step
ꢀ
[
OH ] (as in Table 1) were varied at six different temperatures.
ride. This complex (C
2
ꢀ
The plots of 1/k
U
versus [OH ] and 1/k
U
versus 1/[OMH] should
to give the free radical species of OMH, Ag(II) with the regeneration
of catalyst, Ru(III). Further this free radical species of OMH reacts
with Ag(II) in a fast step to form 4-aminobutyraldehyde intermedi-
ate. This intermediate reacts with one mole of DPA in a further fast
step to form the products such as 4-aminobutyric acid, Ag(I) and
periodate as given in Scheme 3. The reduction of Ru(III) to lower
oxidation state and then regeneration of Ru(III) by oxidant was
not possible under the experimental conditions due to observed
orders in different constituents of reaction.
be linear (Fig. 5). From the slopes and intercepts, the values of K
and K were calculated at different temperatures and these values
are given in Table 3. The vant Hoff’s plots were made for variation
of K and K with temperature (logK versus 1/T (r P 0.991,
S 6 0.004) and logK versus 1/T (r P 0.989, S 6 0.005)) and the val-
ues of enthalpy of reaction H, entropy of reaction S and free en-
ergy of reaction G, were calculated for the first and second
equilibrium steps. These values are given in Table 3. A comparison
1
2
1
2
1
2
D
D
D
ꢀ
1
of the
that of
D
H value of second step (40.6 k J mol ) of Scheme 2 with
The probable structure of the complex (C
2
) is given as,
#
ꢀ1
DH (47.2 k J mol ) obtained for the slow step of the reac-
tion shows that these values mainly refer to the rate limiting step,
supporting the fact that the reaction before rate determining step
is fairly fast and involves low activation energy [32].
+
OH2
Ru
O
C
OH2
OH
NH2
4.2. Mechanism for Ru(III) catalyzed reaction
O
Ruthenium(III) chloride acts as an efficient catalyst in many
H
2
O
OH
2
NH2
OH2
redox reactions, particularly in an alkaline medium [24]. It is inter-
esting to identify the probable ruthenium(III) chloride species in
alkaline media. In the present study it is quite probable that the
2
+
[
[
Ru(H
Ru(III)(OH)
2
O)
5
OH]
species might assume the general form
. The x value would always be less than six be-
3
ꢀ x
x
]
cause there are no definite reports of any hexahydroxy ruthenium
species. The remainder of the coordination sphere would be filled
by water molecules. At higher pH, the electronic spectra studies
have confirmed [34] that the ruthenium(III) chloride exists in the
Spectroscopic evidence for the complex formation between
Ru(III) and OMH was obtained from UV–Vis spectra of OMH
ꢀ4
ꢀ6
ꢀ
ꢀ3
(5.0 ꢁ 10 ), Ru(III) (3 ꢁ 10 , [OH ] = 0.08 mol dm ) and a mix-
ture of both. A hypsochromic shift of 5 nm from 277 to 272 nm
in the spectra of Ru(III) to the mixture of Ru(III) and OMH was ob-
served (Fig. 6). Attempts to separate and isolate the complex were
not successful. The Michaelis–Menten plot proved the complex for-
mation between catalyst and substrate, which explains less than
unit order in [OMH]. Such a complex between a catalyst and sub-
strate has also been observed in other studies [36]. The rate law
(11) for the Scheme 3 could be derived as,
3+
3+
hydrated form as [Ru(H
are also known to exist as [Ru(H
2
O)
6
]
. Metal ions of the form [Ru(H
2
O) ]
6
OH]2 in an alkaline medium
+
2
O)
5
and are most likely mononuclear species. Hence, under the condi-
ꢀ
tions employed, e.g. [OH ] ꢃ [Ru(III)], ruthenium(III) is mostly
+
present as the hydroxylated species, [Ru(H
O)
2 5
OH]2 . Similar spe-
cies have been reported between Ru(III) catalyzed oxidation of sev-
eral other substrates with various oxidants in alkaline medium
[
35]. In earlier reports of Ru(III) catalyzed oxidation [16], it has
been observed that, if there is a fractional order dependence with
respect to [substrate] and Ru(III) and unit order with respect to
ꢀd½DPAꢂ
k
K
2
K
3
K
4
½OMHꢂ½RuðIIIÞꢂ½DPAꢂ
rate ¼
¼ K
3
ꢀ
ꢀ
dt
þ K
3
4
½OMHꢂ þ ½OH ꢂ þ K
4
½OMHꢂ½OH ꢂ
[
oxidant], Ru(III) forms a complex with the substrate. It gets oxi-
ð10Þ
dized by the oxidant to form Ru(IV)–substrate complex followed
by the rapid redox decomposition to regenerate Ru(III). In another
case [17], if the process shows a zeroth order dependence with re-
spect to [oxidant], first order with respect to [Ru(III)] and a frac-
tional order with respect to [substrate], there involves the
formation of a Ru(III)–substrate complex. It undergoes further
cleavage in a concerted manner giving rise to a Ru(I) species, which
is rapidly oxidized by the oxidant to regenerate the catalyst. In
some other reports [18], it is observed that Ru(III) forms a complex
with substrate and is oxidized by the oxidant with the regenera-
tion of the catalyst. Hence, the study of behavior of Ru(III) in cata-
lyzed reaction becomes significant.
rate
DPAꢂ
k
2
K
3
K
4
½OMHꢂ½RuðIIIÞꢂ
¼ k ¼ k ꢀ k
C
T
U
¼
ꢀ
½OMHꢂ½OHꢀꢂ
ð11Þ
½
K
3
þ K
3
K
4
½OMHꢂ þ ½OH ꢂ þ K
4
This explains all the observed kinetic orders of different species. The
rate law (11) can be rearranged to be Eq. (12), which is suitable for
verification
ꢀ
ꢀ
½
RuðIIIÞꢂ
½OH ꢂ
½OH ꢂ
1
1
¼ k
þ
þ K
þ k
2
ð12Þ
k
C
2
K
3
K
4
½OMHꢂ
k
2
K
3
3
K
4
½OMHꢂ
The equilibrium step 1 and the stoichiometry were same as in
the case of uncatalyzed reaction. In the Ru(III) catalyzed reaction,
According to Eq. (12), other conditions being constant, the plots
ꢀ
of [Ru(III)]/k
C
versus [OH ] and [Ru(III)]/k
C
versus 1/[OMH] should
[
DPA] was first order dependence, an apparent order of less than
be linear and found to be so (Fig. 7). From the intercepts and slopes
of such plots, the reaction constants K , K and k were calculated
(9.8 ± 0.3) ꢁ 10 dm mol
, respectively. These constants were
unit order in [OMH], a negative fractional order dependence on [al-
kali] and order with respect to Ru(III) was found to be unity. No ef-
fect of added products was observed. Based on the experimental
3
4
2
ꢀ
2
ꢀ3
2
3
ꢀ1
as
(3.4 ± 0.1) ꢁ 10 mol dm
,
,
4
3
ꢀ1 ꢀ1
(4.8 ± 0.2) ꢁ 10 dm mol
s

S.J. Malode et al. / Inorganica Chimica Acta 363 (2010) 2430–2442
2439
K3
2-
-
-
[
Ag(H IO )(H IO )] + H O
[Ag(H IO ) ] + [OH ]
3 6 2
2
6
3
6
2
K4
NH2
COO-
2+
Complex(C2)
+
[Ru(H O) OH]
2
5
NH2
k2
-
NH2
+ Ag(II) + CO + 2H IO
6
2-
Complex(C ) + [Ag(H IO ) ]
2
3
2
3
6 2
slow
.
2+
+
[Ru(H O) OH]
2 5
NH2
fast
OH
NH2
NH2
+ Ag(II)
+ NH + Ag(I)
3
.
-
CHO
NH2
fast
OH-
NH2
2-
NH2
-
+ Ag(I) + 2H IO + H O
3
6
2
+ [Ag(H IO ) ]
3
6 2
2
COOH
CHO
Scheme 3. Detailed Scheme for Ru(III) catalyzed oxidation of DL-ornithine by alkaline diperiodatoargentate(III).
A
2
1
1
0
0
.4
.8
.2
.6
.0
288 K
293 K
298 K
k
303 K
308 K
313 K
0
.0
0.4
0.8
1.2
1.6
-4
3
-1
1
/[OMH] x 10 (dm mol )
B 0.6
Fig. 6. Spectroscopic evidence for the complex formation between Ru(III) and OMH.
a) UV–Vis spectra of Ru(III) (327, 277 and 229 nm); (b) UV–Vis spectra of mixture
of Ru(III) and OMH (327, 272 and 229 nm); and (c) UV–Vis spectra of OMH.
(
288 K
0
0
0
.4
.2
.0
used to calculate the rate constants and compared with the exper-
imental k
C
values and found to be in reasonable agreement with
293 K
98 K
each other, which fortifies Scheme 3.
2
The thermodynamic quantities for the different equilibrium
steps, in Scheme 3 can be evaluated as follows. The DL-ornithine
monohydrochloride and hydroxide ion concentrations (Table 2)
k
303 K
308 K
313 K
were varied at different temperatures. The plots of [Ru(III)]/k
C
ver-
ꢀ
sus 1/[OMH] (r P 0.9982, S 6 0.00132), [Ru(III)]/k
C
versus [OH ]
(
r P 0.9873, S 6 0.00145) should be linear as shown in Fig. 7. From
0
0.3
0.6
[OH ] x 10 (mol dm )
0.9
1.2
3
the slopes and intercepts, the values of K are calculated at differ-
-
-3
ent temperatures. A vant Hoff’s plot was made for the variation of
with temperature [i.e., logK versus 1/T (r P 0.961, S 6 0.1035)]
and the values of the enthalpy of reaction H, entropy of reaction
S and free energy of reaction G, were calculated. These values
are also given in Table 4. A comparison of the H value of second
K
3
3
Fig. 7. Verification of rate law (12) for the Ru(III) catalyzed oxidation of DL-ornithine
monohydrochloride by diperiodatoargentate(III). Plots of (A) [Ru(III)]/k
OMH], (B) [Ru(III)/k
D
C
vs 1/
D
D
ꢀ
[
C
vs [OH ], at six different temperatures (conditions as given in
D
Table 2).
ꢀ1
#
ꢀ1
step (31.5 k J mol ) of Scheme 3 with that of
DH (49.6 k J mol )
obtained for the slow step of the reaction shows that these values
mainly refer to the rate limiting step, supporting the fact that the
reaction before rate determining step is fairly fast and involves
culated at different temperatures and the corresponding values of
thermodynamic quantities are given in Table 4. The positive value
#
of
D
S is normal in case of fast reactions [37] involving distribution
low activation energy [18]. In the same manner, K
4
values were cal-
of charges as given in Scheme 3.

2
440
S.J. Malode et al. / Inorganica Chimica Acta 363 (2010) 2430–2442
The negligible effect of ionic strength might be due to the
A
presence of various ions in both catalyzed and uncatalyzed reac-
tions (Schemes 2 and 3). But in case of Ru(III) catalyzed reaction,
the rate constants decreased with decrease in dielectric constant
of the medium. The effect of solvent on the reaction rate has
been described in detail in the literature [38]. For the limiting
case of a zero angle approach between two dipoles or anion–di-
4.0
(4)
3
3
.8
.7
k
(3)
C
pole system, Amis [38] has shown that a plot of logk versus 1/D
gives a straight line, with a negative slope for a reaction be-
tween a negative ion and a dipole or two dipoles, and with a po-
sitive slope for positive ion and dipole interaction. In the present
study, the plot observed had a negative slope, which supports
the involvement of negative ions as given in Scheme 3. The
(2)
(1)
#
#
moderate
DH and DS values are favorable for electron transfer
#
3.5
reaction. The value of
D
H
was due to energy of solution
3
.4
3.6
3.7
3.9
changes in the transition state. The observed modest enthalpy
of activation and a higher rate constant for the slow step indi-
cates that the oxidation presumably occurs via an inner-sphere
mechanism. This conclusion is supported by earlier observations
3
+ log
k
1
8
.0
B
[
39]. The activation parameters evaluated for the catalyzed and
uncatalyzed reactions explain the catalytic effect on the reaction.
The catalyst Ru(III) forms the complex (C ) with substrate which
2
6.0
(
4)
enhances the reducing property of the substrate than that with-
out catalyst. Further, the catalyst Ru(III) modifies the reaction
path by lowering the energy of activation.
k
4
.0
The values of activation parameters for the uncatalyzed and
ruthenium(III) catalyzed oxidations of some amino acids by DPA
are summarized in Tables 6 and 7. The entropy of the activation
for the title reaction falls within the observed range. Variation in
the rate within a reaction series may be caused by change in the
enthalpy or entropy of activation. Changes in the rate are caused
(
3)
2.0
0.0
(
2)
(1)
#
#
by changes in both
DH and DS , but these quantities vary exten-
#
#
sively in a parallel fashion. A plot of
according to equation
D
H
versus
D
S
is linear
0.0
2.0
4.0
6.0
8.0
3
+ logk
1
#
#
Fig. 8. Plots of (A) logk2 at 303 K vs logk1 at 298 K for uncatalyzed reaction
conditions as given in Table 6); (B) logk at 303 K vs logk at 298 K for
ruthenium(III) catalyzed reaction (conditions as given in Table 7); for (1) -alanine;
D
H
¼ bD
S
þ constant
(
2
1
L
(
2)
L-leucine; (3)
L-lysine; and (4) DL-ornithine.
where b is called the isokinetic temperature. It has been asserted
#
#
that apparently linear correlation of
DH with DS are sometimes
misleading and the evaluation of b by means of the above equation
lacks statistical validity [40]. Exner [41] advocates an alternative
method for the treatment of experimental data. If the rates of sev-
eral reactions in a series have been measured at two temperatures
and logk
blogk
2
2 1 1 2
(at T ) is linearly related to logk (at T ), i.e., logk = a + -
1
, he proposes that b can be evaluated from the equation,
b ¼ T
1
T
2
ðb ꢀ 1Þ=T
2
b ꢀ T
1
Table 6
Activation parameters for the oxidation of some amino acids by diperiodatoargentate(III) (for isokinetic temperature).
ꢁ 10 (dm3 mol
3
ꢀ1 ꢀ1
s
) at 298 K
k
2
ꢁ 10 (dm3 mol
3
ꢀ1 ꢀ1
s
) at 303 K
D
H# (k J molꢀ1
)
D )
S# (J K mol
ꢀ1
ꢀ1
Reference
Amino acids
k
1
L
L
L
-Alanine
-Leucine
-Lysine
3.04
4.29
4.02
6.83
3.66
4.98
5.50
9.44
24
ꢀ212
ꢀ225
ꢀ169
ꢀ127
[43]
19.4
36
[43]
[44]
DL-Ornithine
47
Present work
Table 7
Activation parameters for the Ru(III) catalyzed oxidation of some amino acids by diperiodatoargentate(III) (for isokinetic temperature).
ꢁ 10ꢀ (dm3 mol
4
ꢀ1 ꢀ1
s
) at 298 K
k
ꢁ 10ꢀ4 (dm3 mol
ꢀ1 ꢀ1
s
) at 303 K
D
H# (k J molꢀ1
12
9.3
5.87
49.2
)
D )
S# (J K mol
ꢀ1
ꢀ1
Reference
Amino acids
k
1
2
L-Alanine
L-Leucine
L-Lysine
0.0218
0.100
0.0271
0.108
ꢀ128
ꢀ155
ꢀ142
[45]
[45]
1.9768
4.8160
2.0767
6.7523
[45]
DL-Ornithine
11.38
Present work

S.J. Malode et al. / Inorganica Chimica Acta 363 (2010) 2430–2442
2441
We have calculated the isokinetic temperatures as 269.4 K by
plotting logk at 303 K versus logk at 298 K for uncatalyzed and
50.9 K by plotting logk at 303 K versus logk at 298 K for Ru(III)
catalyzed (Fig. 8). The values of b for both uncatalyzed (269.4 K)
and Ru(III) catalyzed (150.9 K) are lower than experimental tem-
perature (298 K). This indicates that both the rates are governed
by the entropy of activation [42]. The linearity and the slope of
the plot obtained may confirm that the kinetics of these reactions
follow similar mechanism, as previously suggested.
The total concentration of DPA is given by (where T and F stand for
total and free)
2
1
1
2
1
ꢀ½
ꢀ
ꢁ
OH ꢂ þ K
4
ꢀ
½DPAꢂ ¼ ½DPAꢂ þ ½AgðH IO Þ ꢂ ¼ ½DPAꢂF
3
6
T
F
2
ꢀ
½
OH ꢂ
Therefore,
ꢀ½
ꢁ
ꢀ
DPAꢂ ½OH ꢂ
T
½
DPAꢂ ¼
ðB:2Þ
F
ꢀ
½
OH ꢂ þ K
3
Similarly,
5
. Conclusion
½
OMHꢂ ¼ ½OMHꢂ þ ½C
2
ꢂ ¼ ½OMHꢂ þ K
4
½OMHꢂ ½RuðIIIÞꢂ
T
F
F
F
The comparative study of uncatalyzed and ruthenium(III) cata-
¼
½OMHꢂ ½1 þ K
4
½RuðIIIÞꢂ
F
lyzed oxidation of DL-ornithine monohydrochloride by diperiodat-
oargentate(III) was studied. Oxidation products were identified.
In view of low concentration of Ru(III) used,
Among the various species of Ag(III) in alkaline medium, DPA itself,
½
OMHꢂ ¼ ½OMHꢂ
ðB:3Þ
ꢀ
T
F
i.e., [Ag(H
IO
3 6
)
2
]
is considered as active species for the title reac-
2
+
tion. Active species of Ru(III) is found to be [Ru(H
2 5
O) OH] . It be-
Similarly,
comes apparent that the role of pH in the reaction medium is
crucial. Thermodynamic activation parameters of individual steps
in the mechanisms were evaluated for uncatalyzed and Ru(III) cat-
alyzed reactions at different temperatures, respectively. The cata-
lytic constants and the activation parameters with reference to
catalyst were also computed. The descriptions of the mechanisms
are consistent with all the experimental evidences including ki-
netic, spectral and product studies.
ꢀ
ꢀ
½
½
OH ꢂ ¼ ½OH ꢂ
ðB:4Þ
ðB:5Þ
T
F
RuðIIIÞꢂ ¼ ½RuðIIIÞꢂ þ ½C
2
ꢂ ¼ ½RuðIIIÞꢂ þ K
4
½OMHꢂ½RuðIIIÞꢂF
T
F
F
ꢀ
ꢁ
½RuðIIIÞꢂ
T
½
RuðIIIÞꢂ ¼
F
f1 þ K ½OMHꢂg
4
Substituting Eqs. (B.2)–(B.5) in Eq. (B.1) and omitting the subscripts
T and F, we get
rate
½DPAꢂ
k
2
K
3
K
4
½OMHꢂ½RuðIIIÞꢂ
¼
k
C
¼ k
T
ꢀ k ¼
U
ꢀ
ꢀ
Appendix A
K þ k K ½OMHꢂ þ ½OH ꢂ þ K ½OMHꢂ½OH ꢂ
3
3
4
4
According to Scheme 2
2
ꢀ
References
ꢀ
d½DPAꢂ
k
1
K
1
K
2
½OMHꢂ½AgðH
2
IO
6
ÞðH
3
IO
6
Þꢂ
rate ¼
¼
ꢀ
dt
½OH ꢂ
ðA:1Þ
ðA:2Þ
[
1] D.S. Mahadevappa, K.S. Rangappa, N.N.M. Gowda, B. Thimmegowda, Int. J.
Chem. Kinet. 14 (1982) 1183–1197.
ꢀ
½
DPAꢂ ¼ ½DPAꢂ þ ½AgðH
3
IO
6
Þ ꢂ þ ½C
1
ꢂ
T
F
2
[
[
2] M.K. Mahanti, D. Laloo, J. Chem. Soc., Dalton Trans. (1990) 311–314.
3] R. Medda, A. Padiglia, A. Lorrai, A. Finazzi Agro, G. Floris, J. Protein Chem. 19
where T and F refer to total and free concentrations.
(
2000) 51–57.
ꢀ
½
ꢁ
[
4] B. Sethuram, Some Aspects of Electron Transfer Reactions Involving Organic
Molecules, Allied Publishers (P) Ltd., New Delhi, 2003. p. 151.
5] P.K. Jaiswal, K.L. Yadava, Talanta 17 (1970) 236–238.
6] P.K. Jaiswal, Analyst 1 (1972) 503–506.
K
1
K
1
K
2
½OMHꢂ
½
DPAꢂ ¼ ½DPAꢂF 1 þ
þ
ꢀ
T
ꢀ
ꢀ
½
OH ꢂ
½OH ꢂ
[
[
DPAꢂ ½OH ꢂ
T
½
DPAꢂ ¼
[7] P. Jayaprakash Rao, B. Sethuram, T. Navneeth Rao, React. Kinet. Catal. Lett. 29
1985) 289–296.
F
ꢀ
½
OH ꢂ þ K
1
þ K
1
K
2
½OMHꢂ
(
[
[
8] K. Venkata Krishna, P. Jayaprakash Rao, Indian J. Chem. 37A (1998) 1106–1110.
9] A. Kumar, P. Kumar, P. Ramamurthy, Polyhedron 18 (1999) 773–780.
Similarly,
[
10] A. Kumar, P. Kumar, J. Phys. Org. Chem. 12 (1999) 79–85.
[11] A. Kumar, P. Vaishali, P. Ramamurthy, Int. J. Chem. Kinet. 32 (2000) 286–293.
12] A.K. Das, Coord. Chem. Rev. 213 (2001) 307–325.
½
OMHꢂ ¼ ½OMHꢂ þ ½C
1
ꢂ
T
F
ꢀ
ꢁ
ꢀ
[
½
OH ꢂ
½OMHꢂ ¼ ½OMHꢂT
[13] K.N. Shivananda, B. Lakshmi, R.V. Jagdeesh, Puttaswamy, K.N. Mahendra, Appl.
Catal. A: Gen. 326 (2) (2007) 202–212.
[
F
ꢀ
½
OH ꢂ þ K
1 2
K
½DPAꢂF
14] P.K. Tandon, A. Mehrotra, M. Srivastava, M. Dhusia, S.B. Singh, Transition Met.
Chem. 32 (2007) 991–999.
In view of low concentrations of DPA used, the second term of above
equation is neglected.
Therefore,
[15] A.K. Singh, S. Srivastava, J. Srivastava, R. Srivastava, P. Singh, J. Mol. Catal. A:
Chem. 278 (2007) 72–81.
[
16] S. Sandu, B. Sethuram, T.N. Rao, J. Indian Chem. Soc. 60 (1983) 198–200.
½
OMHꢂ ¼ ½OMHꢂF
ðA:3Þ
ðA:4Þ
[17] H.P. Panda, B.D. Sahu, Indian J. Chem. 28A (1989) 323–324.
T
[
18] V. Tegginamath, C.V. Hiremath, S.T. Nandibewoor, J. Phys. Org. Chem. 20
(2007) 55–64.
Similarly,
ꢀ
ꢀ
[19] C.S. Reddy, T. Vijaykumar, Indian J. Chem. 34A (1995) 615–620.
½
OH ꢂ ¼ ½OH ꢂ
T
F
[
[
[
20] G.P. Panigrahi, P.K. Misro, Indian J. Chem. 15A (1977) 1066–1069.
21] G.L. Cohen, G. Atkinson, Inorg. Chem. 3 (12) (1964) 1741–1743.
22] L.J. Bellamy, The Infrared Spectra of Complex Molecules, Methuen and Co. Ltd.,
London, 1958. p. 162.
Substituting Eqs. (A.2)–(A.4) in Eq. (A.5) and omitting the subscripts
T and F we get
[
23] G.H. Jeffery, J. Bassett, R.C. Denney, Vogel’s Text Book of Quantitative Chemical
Analysis, 5th ed., ELBS, New York, 1996. p. 679.
ꢀ
d½DPAꢂ
k
1
K
1
K
2
½OMHꢂ½DPAꢂ
þ K ½OMHꢂ
rate ¼
¼
ðA:5Þ
ꢀ
dt
½OH ꢂ þ K
1
1
K
2
[24] R.V. Jagadeesh, Puttaswamy, J. Phys. Org. Chem. 21 (2008) 844–858.
[
25] E.A. Moelwyn-Hughes, Kinetics of Reactions in Solutions, Oxford University
Press, London, 1947. p. 297.
[
[
26] L.J. Krishenbaum, L. Mrozowski, Inorg. Chem. 17 (1978) 3718–3719.
27] R. Banerjee, R. Das, S. Mukhopadhyay, J. Chem. Soc., Dalton Trans. (1992)
Appendix B
1317–1322.
[
[
28] C.E. Crouthamel, A.M. Hayes, D.S. Martin, J. Am. Chem. Soc. 73 (1951) 82–87.
29] S. Bhattacharya, B. Saha, A. Datta, P. Banerjee, Coord. Chem. Rev. 170 (1998)
47–74.
According to Scheme 3
k
2
K
3
K
4
½OMHꢂ½RuðIIIÞꢂ½DPAꢂ
ꢀ
rate ¼ k
2
½C
2
ꢂ½AgðH
3
IO
6
Þ ꢂ
¼
ðB:1Þ
[30] R. Chang, Physical Chemistry with Applications to Biological Systems,
McMillan, New York, 1981. p. 326.
2
ꢀ
½
OH ꢂ

2
442
S.J. Malode et al. / Inorganica Chimica Acta 363 (2010) 2430–2442
[
[
[
31] N.P. Shetti, R.N. Hegde, S.T. Nandibewoor, Inorg. Chim. Acta 362 (2009) 2270–
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Reactions in Techniques of Chemistry, vol. 4, Wiley, New York, 1974. p. 421.
34] R.E. Connick, D.A. Fine, J. Am. Chem. Soc. 82 (1960) 4187–4191.
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Chemistry, 6th ed., John Wiley and Sons Inc., New York, 1999.
[38] E.S. Amis, Solvent Effects on Reaction Rates and Mechanisms, Academic press,
New York, 1966. p. 183.
[39] S.A. Farokhi, S.T. Nandibewoor, Tetrahedron 59 (2003) 7595–7602.
[40] E.S. Lewis, Investigations of Rates and Mechanisms of Reactions, 3rd ed., Wiley,
New York, 1974. p. 415.
[41] O. Exner, Coll. Czech. Chem. Commun. 37 (1972) 1425–1444.
[42] J.E. Leffler, J. Org. Chem. 20 (1955) 1202–1231.
[43] C.V. Hiremath, S.D. Kulkarni, S.T. Nandibewoor, Ind. Eng. Chem. Res. 45 (2006)
8029–8035.
2
[
[
[
[
36] K.N. Vinod, Puttaswamy, Ninge Gowda, J. Mol. Catal. A: Chem. 298 (2009) 60–
[44] D.S. Munavalli, S.A. Chimatadar, S.T. Nandibewoor, Transition Met. Chem. 33
(2008) 535–542.
[45] R.R. Hosamani, S.T. Nandibewoor, J. Chem. Sci. 121 (2009) 275–281.
6
8.
37] K.J. Laidler, Chemical Kinetics, 2nd ed., McGraw-Hill Inc., New York, 1991. p.
37.
2