A novel and Facile oxidation of d-glucose by n-bromophthalimide in the presence of chloro-complex of ruthenium(III)

Article abstract of DOI:10.1080/15533174.2010.522664

Kinetics of oxidation of D-glucose (D-Glu) by N-bromopthalimide (NBP, C₈H₄O₂NBr) in presence of [RuCl ₂(H₂O)₃OH] as a homogenous catalyst in perchloric acid medium has been investigated. The kinetic results indicate that the reaction was first order on [NBP] and zero order on [D-Glu]. The reaction followed first-order kinetics with respect to Ru(III) chloride in its lower concentration range and tends to zero-order at its higher concentration. Negative effect of [H⁺] and [Cl^-] ions on the rate of oxidation were observed, whereas change of ionic strength (μ) of the medium had no effect on the oxidation velocity. The values of rate constants observed at five different temperatures (298, 303, 308, 313, 318 K) were utilized to calculate the activation parameters. Formic acid and arabinonic acid have been identified as the main oxidation products of the reaction. A plausible mechanism from the results of kinetic studies, reaction stoichiometry, and product analysis has been proposed. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/15533174.2010.522664

Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 40:947–954, 2010
Copyright © Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2010.522664
A Novel and Facile Oxidation of D-glucose by
N-bromophthalimide in the Presence of Chloro-complex of
Ruthenium(III)
1
2
3
4
Ajaya Kumar Singh, Neerja Sachdev, Alpa Shrivastava, Yokraj Katre, and
5
Surya P. Singh
1
Department of Chemistry, Govt. V. Y .T. PG. Autonomous College, Durg (C.G.), India
Department of Chemistry, Shri Shankaracharya Mahavidyalaya, Bhilai, India
Department of Applied Chemistry, Shri Shankaracharya College of Engineering & Technology,
2
3
Bhilai, India
4
Department of Chemistry, Kalyan Mahavidyalaya, Bhilai Nagar, Bhilai, India
Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita,
5
Osaka, Japan
in oxidation of several organic compounds by various oxidants
Kinetics of oxidation of D-glucose (D-Glu) by N- is of great interest. In the present work, we have used Ru(III)
bromopthalimide (NBP, NBr) in presence of chloride as a homogeneous catalyst to study the oxidation of
RuCl (H O) OH] as a homogenous catalyst in perchloric
8 4 2
C H O
[
2
2
3
D-Glu by NBP in the acidic medium. Though Ru(III) chloride
is a known nontoxic homogenous catalyst, scant attention has
acid medium has been investigated. The kinetic results indicate
that the reaction was first order on [NBP] and zero order on
been paid to explore the catalytic role of Ru(III) with N-halo
[
D-Glu]. The reaction followed first-order kinetics with respect
to Ru(III) chloride in its lower concentration range and tends to compounds as oxidant.[
1,2]
Ruthenium(III) is an efficient cata-
+
[3]
zero-order at its higher concentration. Negative effect of [H ] and lyst in several redox reactions. The implication of Ru(III) in
−
[
Cl ] ions on the rate of oxidation were observed, whereas change
electron transfers in functional mimicry of biological molecules
of ionic strength (µ) of the medium had no effect on the oxidation
velocity. The values of rate constants observed at five different
temperatures (298, 303, 308, 313, 318 K) were utilized to calculate
[4,5]
in enzymatic system has been suggested.
The mechanisms
of catalytic reactions are complex due to the formation of dif-
the activation parameters. Formic acid and arabinonic acid have ferent intermediate complexes, free radicals, and also different
been identified as the main oxidation products of the reaction. A oxidation state of ruthenium. The mechanism of the reaction
plausible mechanism from the results of kinetic studies, reaction
stoichiometry, and product analysis has been proposed.
depends upon the nature of the substrates and oxidant as well as
upon the ways in which transition metal complex ions play their
role in order to promote the reactant molecules to the activated
Keywords D-glucose, HClO
4
,
N-bromopthalimide, oxidation,
state before finally changing in to products under experimental
Ru(III)
conditions.[
6]
Carbohydrates are important biological substances whose
microbiological and physiological activities depend largely on
their redox behavior.[ The study of carbohydrates is one of the
most exciting fields of organic chemistry. Vast literature is avail-
able on the kinetics of oxidation of carbohydrates by various
INTRODUCTION
Recently, the use of transition metal ions, such as Os(VIII),
Ru(III), Ru(VIII), Ir(III), and Pd(II), as homogeneous catalysts
7]
organic and inorganic oxidants.[
8−9]
D-Glu is a monosaccha-
ride with wide synthetic applications and plays an active role in
biological systems. Oxidation of D-Glu is of great importance
Received 27 May 2010; accepted 27 July 2010.
The authors are thankful to DST-FIST for providing us instrumental both from a chemical and biological point of view. Considering
facilities for research work in our Chemistry Department. The authors its importance for life on earth, the reaction involving carbohy-
wish to thank reviewers for the critical and useful comments that greatly
refined the manuscript.
Address correspondence to Ajaya Kumar Singh, Department of
Chemistry, Govt. V. Y .T. PG. Autonomous College, Durg (C.G.),
India. E-mail: ajayaksingh au@yahoo.co.in
[10−12]
drates are of considerable interest.
The catalyzed and uncatalyzed oxidation of sugars has been
studied in detail by using N-halo compounds.[
7,11,13]
Reports
regarding Ru(III)-catalyzed oxidation of organic compounds by
947

948
A. K. SINGH ET AL.
acidic solution of N-bromosuccinimide[14] are also available in Stoichiometry and Product Analysis
the literature. The chemistry of NBP has evoked considerable
Different ratios of NBP to D-Glu were kept in equilibrium
interest, which acts as a moderate oxidizing and brominating at 303 K (± 0.1) in the presence of requisite amount of perchlo-
agent. A survey of literature shows that no report available on the ric acid, mercuric acetate, and acetic acid under the condition
kinetics of Ru(III)-catalyzed oxidation of D-Glu by NBP. Hence, of [NBP]>>[D-Glu] for 48 h. Determination of unconsumed
wefelt it wouldbeworthwhileto investigatethe oxidativebehav- NBP revealed that two moles of NBP were required for the
ior of NBP with D-Glu to explore the kinetics and mechanistic oxidation of each mole of D-Glu. Accordingly, the following
aspects of the Ru(III) chloride catalyzed reaction. Objectives of stochiometric equation could be formulated:
the present study are (i) to elucidate a plausible mechanism, (ii)
to identify the oxidation product, (iii) to deduce an appropriate
rate law, and (iv) to calculate the activation parameters.
C6H12O6 + 2C8H4O2NBr + 2H2O −→ RCOOH+HCOOH
2C8H4O2NH+2HBr
Arabinonic acid
+
EXPERIMENTAL
where R = C4H9O4.
Materials and Methods
Analytical reagent grade chemicals and double distilled wa-
ter were used throughout the investigation. Solution of NBP
Formic acid and arabinonic acid were identified as the oxi-
dation product in the oxidation of D-Glu. Formic acid was con-
firmed by spot test[
15−16]
and also by TLC methods. Finally, the
(Lancaster, 98%) was prepared in 50% acetic acid and stored
formation of these products was confirmed by GC-MS analysis
in which the reaction mixture was extracted with diethyl ether.
The ether layer was concentrated by slow evaporation before
analyzing with GC-MS, JEOL-JMS (Mate-MS system, Japan).
NHP, i.e., the reduced product of NBP was also identified by
GC-MS.
in a black coated flask to prevent any photochemical deterio-
ration. The prepared solution of NBP was standardized iodo-
metrically. Aqueous solutions of D-Glu were prepared fresh
every day before use. The Ru(III) chloride solution was pre-
pared by dissolving a known weight of Ru(III) chloride (S. D.
fine) in HCl of known strength. Mercury was added to Ru(III)
chloride solution to prevent any Ru(IV) chloride formed during
the preparation of Ru(III) chloride stock solution and was kept
for a day. The Ru(III) chloride concentration was essayed with
Test for Free Radicals
The intervention of free radicals was examined as follows.
EDTA titration and stored in a black coated bottle to prevent The reaction mixture, to which a known quantity of acryl amide
photochemical decomposition. A standard solution of mercuric had been added initially, was kept in an inert atmosphere for
acetate, Hg(OAc)2(Loba chem., Mumbai, India), was acidified 24 h. When the reaction mixture was diluted with methanol, no
with 20% acetic acid. Perchloric acid (GR), which was used in precipitate resulted, suggesting that there is no participation of
+
the reaction as a source of H ions, was diluted with double free radicals in the studied redox reaction.
distilled water.
KINETIC RESULTS
Kinetic Measurements
Oxidation kinetics of D-Glu by NBP has been investigated
The reaction mixture containing the desired volume of all in the presence of acidic solution of Ru(III) chloride at different
reactants, i.e., NBP, perchloric acid (0.05 M), Ru(III) chloride, concentrations of reactants. Throughout the study, the concen-
+
mercuric acetate, acetic acid and water except reducing sugar, tration of reducing sugar and H were taken as large excess of
was taken in a blackened conical flask that was kept in the ther- NBP, and Ru(III) chloride was used as a catalyst .The first order
◦
mostatic water bath at constant temperature 30 ± 0.1 C. The rate constant can be written as
requisite volume of sugar solution was also placed within the
Rate = k1[NBP]n1 = k[NBP] [D − Glu] [Ru] [H ]
n1
n2
n3 + n4
same thermostatic bath at the same temperature. After 30 min-
utes, when the reaction mixture had attained the temperature
of the bath, the required volume of sugar solution was sucked
1
In the case of n being equal to one, k1 will be called as
out by pipette and poured into reaction mixture to initiate the apparent first order rate constant.
reaction. The actual progress of reaction was followed by esti-
The rate of oxidation reaction was found to be first order with
mating the unconsumed NBP iodometrically. The rate constant respect to NBP in all the cases. The plots of log [NBP] versus
in each kinetic run was determined by plotting a graph between time were found to be straight lines, indicating that the order
log [NBP] versus time. Each kinetic run was studied for two with respect to the oxidant was one and from the slope of the
half-lives of the reaction. The observed rates of reaction were lines k1, rate constant was calculated (Figure 1).
within ± 5% in replicate kinetics runs. The order of reaction in
each reactant was determined with the help of log-log plot of k1
versus concentration of reactant.
The value of reaction rate was calculated as:
−dc/dt = k1[NBP]

OXIDATION OF D-GLUCOSE BY N-BROMOPHTHALIMIDE
949
◦
◦
FIG. 1. Plot between remaining log [NBP] versus time at 30 C: [D-Glu] = 2 FIG. 3. Plot of [Ru(III) chloride] versus k at 30 C under experimental con-
1
−
3
−3,
+
−2
−3
−5
−3
−4
−3
−3
−3, +
[H ]
×
10 mol dm [H ] = 5 × 10 mol dm , [KCl] = 1.2 × 10 mol dm
,
dition: [NBP] = 2 × 10 mol dm , [D-Glu] = 2 × 10 mol dm
−
4
−3
−2
−3
−5
−3
[
Hg(OAc)2] = 3 × 10 mol dm , Acetic acid = 20%, [Ru(III) chloride]= = 5 × 10 mol dm , [KCl] = 1.2 × 10 mol dm , [Hg(OAc) ] = 3 ×
2
−
5
−3
−4
−3
1
.92 × 10 mol dm
.
10 mol dm , Acetic acid = 20%.
The first-order dependence of reaction on NBP (from 0.20 – of oxidation (Table 1). It was also observed that on increasing
−
4
−3
−2
−3
2
.00 × 10 mol dm ) was demonstrated by the plot of reac- [HClO4] (from 1.50 – 15.00 × 10 mol dm ) in the reaction
tion rate versus [NBP] (Table 1; Figure 2). Zero order kinetics mixture, the values of k1 decreased, indicating thereby negative
−3
−3
+
−2
−3
with respect to D-Glu (from 2.00– 16.00 × 10 mol dm
)
effect of [H ]( from 1.50 – 15.00 × 10 mol dm ) on the rate
was observed with its variations (Table 1). The reaction follows of reaction (Table 1; Figure 4). The order of reaction with re-
first-order kinetics with respect to [Ru(III)] (from 0.96 – 11.55 spect to hydrogen ion at fixed ionic strength was found as -0.30
− −3
5
+
×
10 mol dm ) in its lower concentration range and tends to from the slope of plot between log k1 and log [H ]. Successive
zero-order at its higher concentration (Table 1). This is evident additions of phthalimide (NHP), mercuric acetate, and acetic
from the plot of k1 versus [Ru(III)] chloride, where straight lines acid (Table 2) showed no effect on the rate of reaction. It has
passing through the origin was obtained (Figure 3). The rate of been reported earlier that Hg(II) can act as a homogeneous cat-
−
reaction decreased with increasing [Cl ] (from 0.10 – 2.00 × alyst, co-catalyst, and oxidant. In order to ascertain the real role
−5
−3
−
−
10
mol dm ), showing negative effect of [Cl ] on the rate of Hg(OAc)2 as a Br scavenger, several experiments were per-
formed with different initial concentrations of Hg(OAc)2 with
and without the presence of NBP under similar experimental
◦
FIG. 2. Plot of (−dc/dt) versus [NBP] at 30 C for the oxidation of D-Glu
−3
−3,
+ ◦
FIG. 4. Plot of k1 versus [H ] at 30 C under experimental condition: [NBP]
under the experimental condition of Table 1. [D-Glu] = 2 × 10 mol dm
+
−2
−3
−5
−3
−4
−3
−3
−3,
[
=
H ] = 5 × 10 mol dm , [KCl] = 1.2 × 10 mol dm , [Hg(OAc)2]
= 2 × 10 mol dm , [D-Glu] = 2 × 10 mol dm
[KCl] = 1.2 ×
−
4
−3
−5
−3
−4
−3
3 × 10 mol dm , Acetic acid = 20%, [Ru(III) chloride] = 1.92 × 10 mol dm , [Hg(OAc)2] = 3 × 10 mol dm , Acetic acid = 20%,
−
5
−3
−5
−3
.
1
0
mol dm
.
[Ru(III) chloride]= 1.92 × 10 mol dm

950
A. K. SINGH ET AL.
TABLE 1
◦
Effect of variation of [NBP], [D-Glu], and [Ru(III) chloride] on the rate constant at 30 C
4
3
5
+
2
5
[
NBP] × 10
[D-Glu] × 10
[RuCl3] × 10
[H ] × 10
[KCl] × 10
−
3
−3
−3
−3
−3
4
−1
mol dm
mol dm
mol dm
mol dm
mol dm
k1 × 10 s
0.20
0.50
1.00
1.50
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
4.00
8.00
16.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
1.92
1.92
1.92
1.92
1.92
1.92
1.92
1.92
1.92
0.96
1.92
3.85
4.62
5.77
8.32
11.55
1.92
1.92
1.92
1.92
1.92
1.92
1.92
1.92
1.92
1.92
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
1.50
3.00
5.00
10.00
15.00
5.00
5.00
5.00
5.00
5.00
1.20
1.20
1.20
1.20
1.20
1.20
1.20
1.20
1.20
1.20
1.20
1.20
1.20
1.20
1.20
1.20
1.20
1.20
1.20
1.20
1.20
0.10
0.20
0.40
1.20
2.00
1.15
1.03
1.12
1.13
1.15
1.15
1.12
1.05
1.10
0.56
1.18
2.60
3.25
3.90
4.20
4.50
1.65
1.38
1.15
0.92
0.82
12.5
3.00
2.10
0.90
0.43
Reaction condition: [D-Glu] = 2 × 10 mol dm , [H ] = 5 × 10 mol dm−3, [KCl] = 1.2 × 10−5 mol dm , [Hg(OAc)
−
3
−3
+
−2
−3
] = 3 ×
2
−
4
−3
−5
−3
.
10
mol dm , acetic acid = 20 %, [RuCl
3
] = 1.92 × 10 mol dm
conditions. The kinetic observations showed that the reaction effect of temperature on rate constant was studied in the tem-
rate was almost constant with the increase in concentration of perature range 298–318 K (Table 3). From the linear Arrhenius
Hg(OAc)2, which negates its role as a catalyst and a co-catalyst plot of log k1 verses 1/T (Figure 5), the activation energy (Ea
−
1
in the reaction. Also, the reaction did not proceed under sim- = 64.89 kJ mol ) was calculated. With the help of the energy
#
ilar conditions with Hg(OAc)2 without using NBP; indicating of activation, parameters such as enthalpy of activation (ꢀH =
−1
#
Hg(OAc)2 is not involved as an oxidant. Such kinetic obser- 62.380 kJ mol ), entropy of activation (ꢀS = −225.32 JK
−
−1
#
vations suggest that Hg(OAc)2 acted only as a Br scavenger mol ) and Gibbs free energy of activation (ꢀG = 130.56 kJ
2
− [17] −1
forming [HgBr4]
.
Rate studies were also carried out with mol ) were also calculated.
acetonitrile in different composition (5–40% by volume) in the
reaction mixture, thereby varying the dielectric constant (D) of
the medium. There was no significant effect of D on the rate of
DISCUSSION
reaction. It was observed that acetonitrile was not oxidized by Reactive Species of NBP
It has been reported earlier by several workers[
NBP under the experimental conditions. The negligible effect
of ionic strength ‘µ’ of the medium varied by addition of a re- NBP is a stable and brominating agent because of large polarity
18−19]
that
−
5
−3
−
quired amount of KNO3,i.e., from 0.4–3.2 × 10 mol dm
,
of N-Br bond. NBP is capable of producing Br reasonably
on the rate constant was also observed (Table 2). Activation pa- shows that NBP, like other similar N-halo imides, may exist
rameters are believed to provide useful information regarding in various form in acidic medium, that is free NBP, protonated
the environment in which chemical reactions take place. The NBP, Br , HOBr, (H OBr) . Considering the experimental
+
+
2

OXIDATION OF D-GLUCOSE BY N-BROMOPHTHALIMIDE
951
TABLE 2
◦
Effect of variation of acetic acid, acetonitrile, [Hg(OAc)2], [NHP], and [KNO3] on the rate constant at 30 C
4
4
5
Acetic acid
%,v/v)
Acetonitrile
(%,v/v)
[Hg(OAc)2] × 10
[NHP] × 10
[KNO3] × 10
−
3
−3
−3
4
−1
(
mol dm
mol dm
mol dm
k1× 10 s
10
15
20
25
30
35
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
–
–
–
–
–
3.00
3.00
3.00
3.00
3.00
3.00
3.00
3.00
3.00
3.00
3.00
2.00
3.00
4.00
6.00
8.0.0
12.00
16.00
3.00
3.00
3.00
3.00
3.00
3.00
3.00
3.00
3.00
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
1.13
1.15
1.15
1.10
1.12
1.13
1.13
1.05
1.15
1.14
1.12
1.15
1.14
1.13
1.11
1.15
1.14
1.15
1.13
1.13
1.11
1.12
1.16
1.12
1.15
1.14
1.17
–
5
10
20
30
40
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
1.00
2.00
4.00
8.00
–
–
–
–
–
–
0.4
0.8
2.0
2.4
3.2
–
–
–
Reaction condition: [D-Glu] = 2 × 10 mol dm , [H ] = 5 × 10 mol dm−3, [KCl] = 1.2 × 10−5 mol dm , [Hg(OAc)
−
3
−3
+
−2
−3
] = 3 ×
2
−
4
−3
−5
−3
10
mol dm , acetic acid = 20% , [RuCl
3
] = 1.92 × 10 mol dm
−
observations, NBP can be taken as the reactive species, equilibrium with Cl ion
which leads to a rate law capable of explaining all the kinetic
observations and other effects.
−
−
[
RuCl2(H2O)3OH] + Cl ꢁꢂ [RuCl (H2O)2OH] + H2O
3
Reactive Species of Ruthenium(III) Chloride
A study for the chloro complex of Ru(III) chloride in 0.1 M
With increase in the concentration of chloride ion in our
◦
KCl in the pH range of 0.4–2.0 at 25 C suggested four major
experiments, rate of reaction decreased. The observed negative
effect of the chloride ion suggests that the above equilibrium
is favored towards the left. Therefore, [RuCl2(H2O)3OH] was
the most likely reactive species in the reaction of D-Glu with
NBP.
−
+
species, [RuCl4(H2O)2] ,[RuCl3(H2O)3],[RuCl2(H2O)4] and
2
+ [20] +
[
RuCl(H2O)5]
.
Except for [RuCl2(H2O)4] , the stability of
the species decreased with increase in pH and a high instability
+
at pH 2.0. The [RuCl2(H2O)4] species was, however, quite
stable at pH 2.0, which is in equilibrium with its hydrolyzed
It is reported that Ru(III)[
22−23]
form complexes with the
[21,2]
form [RuCl3(H2O)3OH].
reducing sugar. It has been observed that order with respect to
[D-Glu] is zero throughout its tenfold variation in the present
study. This indicates that D-Glu will not take part in the reaction
+
+
[
RuCl2(H2O)4] + H2O ꢁꢂ [RuCl (H2O)3OH] + H O
2
3
With increase in the concentration of chloride ion, the hy- before the rate-limiting step, but in fast steps it will combine with
−
drolyzed form may also form [RuCl3(H2O)2OH] (C1) through the most reactive complex to form the reaction products.

952
A. K. SINGH ET AL.
Rate Law and Mechanism
On the basis of above discussion and experimental data, a
probable reaction mechanism has been proposed for the Ru(III)
catalyzed oxidation of D-Glu in acidic medium in Scheme 1. In
this scheme, the species C2 is formed from the C1 with the elim-
ination of chloride ion and species C1 and C2 are in equilibrium
having a constant K1 (Eq. 1). The species C2 reacts with NBP
to give a complex C3 with the elimination of proton having an
equilibrium constant K2 (Eq. 2). The negative entropy of activa-
tion in the oxidation of D-Glu by NBP supports such a step. The
species C3 slowly decomposes to give the brominated species,
−
[
RuCl2(OBr)(H2O)2(OH)] (C4) and phthalimide (NHP) (Eq.
3). The sum of steps I–VI results in the consumption of two
molecules of NBP per molecule of D-Glu. This is consistent
with the observed stoichiometry of the oxidation of D-Glu by
NBP.
On the basis of reactions in Scheme 1 and stochiometric
studies, the rate of disappearance of NBP can be expressed as:
◦
FIG. 5. Plot of log k1 versus 1/T at 30 C under experimental condition:
−
4
−3
−3
−3,
+
[
×
NBP] = 2 × 10 mol dm , [D-Glu] = 2 × 10 mol dm
[H ] = 5
−
2
−3
−5
−3
10 mol dm , [KCl] = 1.2 × 10 mol dm , [Hg(OAc)2] = 3 ×
−
4
−3
−5
−3
.
1
0
mol dm , Acetic acid = 20%, [Ru(III) chloride]= 1.92 × 10 mol dm
rate = 2k[C3]
k k2 K1[Ru (III)] [NBP]
[1]
[2]
2
rate =
−
+
−
k[Cl ] + k −2 [H ][Cl ]
K1
-
[
[
RuCl (H O) OH ]
+
H O
[ RuCl (H O) OH ]
+ Cl-
3
2
2
2
2
2
3
(I)
(II)
(
C )
(C2)
1
K2
-
+ H+
RuCl (H O) (OH) (NBP) ]
2 2 2 2
[
RuCl (H O) OH ] +
2
2
3
NBP
(
C )
(C3)
2
k
-
-
[
RuCl (H O) (OH) (NBP) ]
2 2 2 2
[ Ru(OBr)Cl (H O) OH ]
+ NHP
(III)
2
2
2
slow
(
C )
(C4)
3
H
H
+
-
H O
3
[
Ru(OBr)Cl (H O) OH ] + S
[ RuCl2(H2O)3(OH) ] + R
C
C
OH (IV)
2
2
2
OH OBr
(C5)
(
C )
4
H
H
O
O
R
C
c
OH
+
(V)
R-C-H
H-C-OH
O
H
O
Br
(
C )
5
O
NBP/H+
(VI)
RCOOH
R-C-H
Ru(III)
Where R stands for C H O and S stands for D-Glu
4
9 4
SCH. 1.

OXIDATION OF D-GLUCOSE BY N-BROMOPHTHALIMIDE
953
+
◦
−
◦
Fig. 6. Plot of [H ] versus 1/ k1 at 30 C under experimental condition: [NBP]
Fig. 8. Plot of [Cl ] versus 1/ k1 at 30 C under experimental condition:
−
4
−3
−3
−3,
−4
−3
−3
−3,
+
=
2 × 10 mol dm , [D-Glu] = 2 × 10 mol dm
[KCl] = 1.2 ×
[NBP] = 2 × 10 mol dm , [D-Glu] = 2 × 10 mol dm
[H ] = 5 ×
−
5
−3
−4
−3
−2
−3
−4
−3
1
0
mol dm , [Hg(OAc)2] = 3 × 10 mol dm , Acetic acid = 20%, 10 mol dm , , [Hg(OAc)2] = 3 × 10 mol dm , Acetic acid = 20%,
−
5
−3
−5
−3
[
Ru(III) chloride]= 1.92 × 10 mol dm
.
[Ru(III) chloride]= 1.92 × 10 mol dm
.
−
5
−3 −1
−6
−3 −1
s , respectively,
10
mol dm
s
and 3.10 × 10 mol dm
Eq. 2 is the rate law on the basis of which observed kinetic
orders with respect to each reactants of the reaction can very
easily be explained.
for the oxidation of D-Glu.
The effect of changing the solvent composition on the rate
of reaction has been discussed in detail in the well known pub-
lications by Frost and Pearson.[ For the limiting case of zero
angle approach between two dipoles or an ion-dipole system,
On reversing Eq. 2, we have Eq. 3
24]
−
−
+
NBP
rate
1
[Cl ]
[Cl ] [H ]
=
=
+
[3]
[25]
Amis has shown that a plot of log k versus 1/D gives a straight
kobs
2k2K1[Ru(III)]
2k K1 K2[Ru(III)]
line, with a negative slope for a reaction between a negative ion
and a dipole or between two dipoles, while a positive slope re-
sults for a positive ion-dipole interaction. The former concept
agrees with the present investigations. The values of free energy
of activation and enthalpy of activation for the redox system
suggest that the transition state is highly solvated while the
negative entropy of activation indicates that transition state is
highly associated. In the present study, the ionic strength showed
negligible effect on the rate of oxidation, suggesting the in-
volvement of a non-ionic species (NBP) in the rate determining
step.
+
Eq. 3 indicates that if a plot is made between 1/kobs versus [H ],
1
−
/ [Ru(III)] and [Cl ], a linear line with positive intercept on
y-axis will be obtained (Figures 6, 7 and 8). Such linearity in
plots proved the validity of both the rate law and the proposed
reaction scheme. From the values of intercepts and slopes of the
plots, the values of k2K1 and kK1K2 were calculated as 5.26 ×
TABLE 3
Effect of temperature on the rate of oxidation of D-Glu
4
−1
Temperature K
k1× 10 s
298
303
308
313
318
6.10
10.20
13.81
22.06
32.50
−
3
−3,
+
−3
◦
Reaction condition: [D-Glu] = 2 × 10 mol dm [H ]
Fig. 7. Plot of 1/Ru(III) versus 1/ k1 at 30 C under experimental condition:
−
2
−3
−5
−
4
−3
−3
−3,
+
= 5 × 10 mol dm , [KCl] = 1.2 × 10 , mol dm
,
[
×
NBP] = 2 × 10 mol dm , [D-Glu] = 2 × 10 mol dm
[H ] = 5
−
4
−3
−
2
−3
−5
−3
[Hg(OAc) ] = 3 × 10 mol dm , acetic acid = 20%,
10 mol dm , [KCl] = 1.2 × 10 mol dm , [Hg(OAc)2] = 3 ×
2
−
4
−3
−5
−3
.
1
0
mol dm , Acetic acid = 20%.
[Ru(III) chloride]= 1.92 × 10 mol dm

954
A. K. SINGH ET AL.
CONCLUSIONS
8. (a) Bhattacharya, N., and Sengupta, M.L. Ind. J. Chem., 1967, 5A, 554;
b) Shilov, E.A., and Yasnikov, A.A. Urk. Khim. Zh., 1952, 18, 595.
. Singh, S.P., Singh, A.K., and Singh, A.K. J. Carbohydr. Chem., 2009, 28,
78.
(
In light of kinetic observations for the catalytic effect of
Ru(III) on the oxidation of D-Glu by NBP, it has been studied in
acidic medium. Oxidation of D-Glu by NBP does not proceed
in the absence of catalyst, but it becomes facile in the presence
9
2
10. Katre, Y., Singh, M., Patil. S., and Singh, A.K. J. Dispersion Sci. Technol.,
2008, 29, 1412.
of Ru(III) catalyst. The reactive species of oxidant and cata- 11. Gowda, B.T., Damodara, N., and Jyothi, K. Int. J. Chem. Kinet., 2005, 37,
5
72.
lyst have been identified. Oxidation products were identified
and activation parameters were also evaluated. The observed
results have been explained by a plausible mechanism, and the
1
1
2. Sharma, J., and Sah, M.P. J. Ind. Chem. Soc., 1994, 71, 613.
3. Iyengar, T.A., and Puttaswami Mahadewappa, D.S. Carbohydr. Res., 1990,
2
04, 197.
related law has been deduced. Therefore, it can be concluded 14. Sharma, J.P., Singh, R.N.P., Singh, A.K., and Singh, B. Tetrahedron, 1986,
that Ru(III) acts as an efficient catalyst for the oxidation of
D-Glu.
42(10), 2739.
1
1
5. Feigl, F. Spot Tests in Organic Analysis; Elsevier: N.Y., 1966, p 451.
6. Vogel, I. Elementary Practical Chemistry, Part III; Longmans-Green: Lon-
don, 1958, p 73.
REFERENCES
17. Bailar, J.C. The Chemistry of Co-ordination Compounds; Reinhold: N.Y.,
1956, p 14.
18. Das, C.M., Indrasenan, P. Ind. J. Chem. 1986, 25A, 605.
19. Das, C.M., Indrasenan, P. Ind. J. Chem. 1987, 26A, 717.
20. Taqui Khan, M.M., Rama Chandraiah, G., and Rao, A. P. Inorg. Chem.,
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. Singh, A.K., Jain, B., Negi, R., Katre, Y.R., Singh, S.P., and Sharma, V.K.
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2

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