Permanganate transfer and reduction by D-glucose in benzene-cetyltrimethyl- ammoniumbromide aqueous solution: A kinetic study

Article abstract of DOI:10.1002/kin.20325

The addition of cationic surfactant, cetlytrimethylammoniumbromide (CTAB), in benzene and aqueous potassium permanganate solution brought the MnO ₄^- from the aqueous phase to the organic phase. At 525 nm, the absorbance of the organic phase increased until it reached a maximum, and then decreased with [CTAB). The effect of (CTAB] on the reduction of permanganate by D-glucose in a benzene-CTAB system has been studied spectrophotmet-rically. The observed effect on the rate constant is catalytic up to a certain concentration of CTAB; thereafter, a saturation phenomenon is observed with an increased concentration of CTAB. The oxidation reaction obeyed the first-order kinetics with respect to the D-glucose. On addition of H ₂SO₄, there was a decrease in the rate constants. There is evidence for the existence of manganese as a water-soluble colloidal MnC ₂ A detailed mechanism with the associated reaction kinetics is presented and discussed.

Full text of DOI:10.1002/kin.20325

Permanganate Transfer
and Reduction by D-Glucose
in Benzene–Cetyltrimethyl-
ammoniumbromide
Aqueous Solution:
A Kinetic Study
MAQSOOD AHMAD MALIK, ZAHEER KHAN
Department of Chemistry, Jamia Millia Islamia (Central University), Jamia Nagar, New Delhi 110 025, India
Received 25 May 2007; revised 20 November 2007, 19 January 2008; accepted 19 January 2008
DOI 10.1002/kin.20325
Published online in Wiley InterScience (www.interscience.wiley.com).
ABSTRACT: The addition of cationic surfactant, cetlytrimethylammoniumbromide (CTAB), in
benzene and aqueous potassium permanganate solution brought the MnO−4 from the aqueous
phase to the organic phase. At 525 nm, the absorbance of the organic phase increased until it
reached a maximum, and then decreased with [CTAB]. The effect of [CTAB] on the reduction
of permanganate by D-glucose in a benzene–CTAB system has been studied spectrophotmet-
rically. The observed effect on the rate constant is catalytic up to a certain concentration of
CTAB; thereafter, a saturation phenomenon is observed with an increased concentration of
CTAB. The oxidation reaction obeyed the first-order kinetics with respect to the D-glucose.
On addition of H2SO4, there was a decrease in the rate constants. There is evidence for the
existence of manganese as a water-soluble colloidal MnO2. A detailed mechanism with the
ꢀ
C
associated reaction kinetics is presented and discussed.
Chem Kinet 40: 496–503, 2008
2008 Wiley Periodicals, Inc. Int J
compound), in the presence of polymers as well as
the transfer of reagents across the phase boundaries
has been the subject of a large number of investigators
[2–10]. In many respects, these systems may be analo-
gous to catalysis by surfactant aggregates [2]. The uti-
lization of surfactants as a reaction media affects rates,
products, and in some cases stereochemistry of the re-
actions. Micellar reactions in some cases have proved
superior to organic solvents as reaction media to obtain
better yields [11]. It has been established that localiza-
tion and compartmentalization effects, preorientational
INTRODUCTION
The term phase-transfer catalysis was coined to de-
scribe reactions, which are mediated by small quanti-
ties of agents, that transfer one reactant across an inter-
face so that a reaction can take place [1]. The reaction
at interfaces, in cavities of crown ethers (macrocyclic
Correspondence to: Zaheer Khan; e-mail: drkhanchem@yahoo.
co.in.
c
ꢀ
2008 Wiley Periodicals, Inc.

PERMANGANATE TRANSFER AND REDUCTION BY D-GLUCOSE IN BENZENE–CTAB SOLUTION
497
polarity and counter-ion effects, and effects of charged
Rate Measurements
interfaces are the important factors that affect the rate
of electron transfer processes in the presence of surfac-
tants [12–16]. Quaternary ammonium salts used as a
phase transfer catalysts have much in common with the
surfactant quaternary ammonium salts used in a micel-
lar system. Cordes and Dunlop [17] reported the kinetic
effect of certain surface-active quaternary ammonium
salts during micelle formation.
The reactions were started in a glass-stoppered two-
necked flask fitted with a double-walled condenser
to check evaporation. A mixture containing required
amount of CTAB, benzene, permanganate, and wa-
ter was thermally equilibrated at desired tempera-
ture (30 0.1◦C), and to this was added a measured
amount of D-glucose solution, pre-equilibrated at the
same temperature. The reaction volume was always
50 cm3. Over the entire range of this study, reactions
were carried out under pseudo-first-order conditions
using an excess of [D-glucose] over [MnO−4 ]. The
kinetics was followed by monitoring the absorbance
of the remaining permanganate in the aqueous phase
at known time intervals at 525 nm (λmax for MnO4−
and ∈ = 2410 dm3 mol−1 cm−1) on a spectronic 21D
spectrophotometer. The cuvettes had a path length of
5 cm. In most cases, the reaction was followed to
well over 80% completion. Pseudo-first-order rate con-
stants (kobs; s−1) reported here are the slopes of the
log(absorbance) versus time plots. The values of the
average linear regression coefficient, γ ≥ 0.996, were
obtained for each kinetic run. Other experimental de-
tails were the same as described elsewhere [18,19]. The
pH of the reaction mixture was also measured at the end
of each kinetic run, and it was observed that pH drift
during the reaction is very small (within 0.05 units).
Potassium permanganate (a powerful oxidant) so-
lution in crown ether and benzene is stable and has
been extensively used in the oxidation of organic com-
pounds. Herriott and Picker [5] investigated the oxida-
tion of organic compounds by MnO−4 in benzene using
tricaprylmethylammonium chloride and suggested that
two-phase systems can be used directly in the presence
of ammonium ion to maintain [MnO−4 ] in the organic
phase. Recognizing the importance of surface-active
quaternary ammonium salts in surface chemistry, we
carried out the present study with the following aims:
(1) to determine the effect of [CTAB] on the transfer
of permanganate from aqueous to benzene, (2) to in-
vestigate the effect of different variables on the rates
of reduction of permanganate by D-glucose in the pres-
ence of CTAB–benzene system, and (3) to determine
whether the role of CTAB is similar to those of aqueous
medium [18]. The observed results and the probable ex-
planations are detailed in this paper. Incidentally, this
study appears to be the first report of its kind.
Product Identification
At the completion of the reaction between D-glucose
and permanganate, identification of the reaction prod-
uct was carried out by paper chromatography [20].
The aqueous phase of the reaction mixture was used
as a mobile phase. Lactone was identified against
an authentic sample (1,4-D-glucolactone) using 4:1:5
n-butanol–acetic acid–water eluent. A three-stage dip
of AgNO3, NaOH, and Na2S2O3 was used to visualize
the paper chromatograms. In alkaline or weakly acidic
solutions, permanganate changes to Mn(IV), whereas
in a strongly acidic medium, permanganate is further
reduced, forming Mn(II) as the final reduction product
of Mn(VII).
EXPERIMENTAL
Materials
The following analytical-grade chemicals were used
without further purification: benzene (99%; Merck,
Mumbai, India), potassium permanganate (99%
Merck, India), D-glucose (99% Merck, India), per-
chloric acid (Fischer Scientific UK; 70% reagent),
sulfuric acid (90%; Merck, India), sodium fluoride,
cetyltrimethylammonium bromide (Fluka, Germany),
and sodium dodecyl sulfate (SDS) (Fluka). Doubly dis-
tilled (first time from alkaline permanganate) water
was used for the preparation of all reagent solutions.
Permanganate solutions were standardized by titration
against a standard oxalic acid solution and stored in a
dark glass bottle. D-Glucose solutions were prepared
just prior to use. Sulfuric acid solutions were prepared
and standardized by titration with sodium hydroxide to
the phenolphthalein end point. An ELICO LI-120 digi-
tal pH meter fitted with a CH-41 combination electrode
was used for pH measurements.
RESULTS AND DISCUSSION
Transfer of MnO−4 into the Organic Phase
It is well known that quaternary ammonium ions nor-
mally permit water-soluble (permanganate) to solubi-
lize in the organic phase [5,21], i.e., benzene. The pur-
ple benzene can be separated and used for oxidation
reactions under anhydrous conditions. On the other
hand, the two-phase system can be used directly for the
International Journal of Chemical Kinetics DOI 10.1002/kin

498
MALIK AND KHAN
Table I [MnO−4 ] in the Organic Phase at Different
[CTAB] at Three Different Time Intervals for the Transfer
of [MnO−4 ] from the Aqueous (2.0 × 10−4 mol dm−3) to
Organic Phase
105 [MnO−4 ] (mol dm−3
)
Time (min)
40
104 [CTAB]a
(mol dm−3
)
30
50
2.0
4.0
6.0
7.0
8.0
12.0
16.0
24.0
32.0
1.0
1.8
2.5
3.0
5.5
3.5
2.5
1.2
0.9
1.2
2.1
2.7
5.1
6.1
5.6
5.5
2.6
2.0
1.2
2.5
3.8
5.6
7.5
5.8
4.8
2.8
2.3
Figure 1 Variation of absorbance at 525 nm with the change
in [CTAB] in 20 cm3 of benzene. Reaction conditions:
MnO4− (2.0 × 10−4 mol dm−3) and temperature (30◦C).
a Benzene = 40%.
permanganate oxidation of organic reductants. There
is a rapid transfer of the purple cation from aque-
ous to benzene layer on mixing the required amount
of CTAB. Therefore, [MnO−4 ] in the organic phase
was established as follows: In a typical experiment,
ca. 100%. The absorption spectrum of MnO−4 in ben-
zene is very similar to that of aqueous MnO−4 [21,22].
This behavior indicates the transfer of MnO−4 in the
benzene (organic phase) and formation of an ion-
pair complex between the MnO−4 and ( N+(CH3)3)
head group of CTAB through the electrostatic inter-
actions. An increase in absorbance below critical mi-
celle concentration (CMC), that is, submicellar effect,
occurred, which may be because small aggregates of
CTAB surfactant (dimers, trimers, tetramers, and so
on) exist below the CMC. These submicellar aggre-
gates interact physically with the MnO−4 , forming ion-
pairs that in turn give some hydrophobic character to
permanganate. On the other hand, a hydrophobic tail
of small aggregates has a hydrocarbon-like structure.
Thus, we may safely conclude that alkyl chains of
CTAB aggregates are responsible for the solubiliza-
tion/incorporation of CTAB–MnO−4 ion-pair into the
organic phase (benzene). The cationic surfactant of
CTAB acts as an electrostatic sink for the anionic per-
manganate [23]. This is one of the few examples when
MnO−4 can be dissolved in a nonpolar solvent simply
by adding CTAB. Quaternary ammonium salts contain
both liphophilic and hydrophilic moieties. Owing to
their amphiphilic nature, CTAB distributes itself be-
tween the aqueous and organic phase, forms an asso-
ciation complex with the reactive anion (MnO−4 ), and
brings it into the organic phase. A complete under-
standing of phase transfer (the role of CTAB) is not
possible because a number of different interactions,
including those associated with the head group of the
surfactant, are involved.
a solution of MnO−4 (10 cm3, 1.0 × 10−3 mol dm−3
)
was added to a solution containing CTAB (2 cm3;
1.0 × 10−2 mol dm−3) and benzene (40%; total vol-
ume 50 cm3). After shaking the reaction mixture, the
organic layer became purple, indicating the transfer of
MnO−4 from the aqueous to benzene layer. As can be
seen from Fig. 1 (a typical example) (λmax = 525 nm
for MnO−4 ), the absorbance of the benzene layer first
increased until it reached a maximum and then de-
creased with [CTAB]. The decrease in [MnO−4 ] in ben-
zene may be due to less partition of MnO−4 from the
aqueous medium owing to a higher aggregate struc-
ture of CTAB. This behavior may be attributed to the
formation of ion-pair between the positive head group
of CTAB and MnO−4 with increasing surfactant con-
centration, which in turn increases the solubilization of
the ion-pair into the organic phase through hydropho-
bic interactions. The wavelength (525 nm) was chosen
to confirm the fulfillment of the Beer–Lambert law and
also to calculate MnO−4 in the benzene phase by moni-
toring the absorbance of different solutions of MnO−4 .
The law is obeyed for the concentration range used
in the present investigations. From the Beer–Lambert
plot, MnO−4 has been calculated to be 0.75 × 10−4
mol dm−3 at constant CTAB (8.0 × 10−4 mol dm−3).
The observed results are summarized in Table I.
It has been established that permanganate trans-
ferred into an immiscible phase (benzene) using qua-
ternary ammonium salts and CTAB. In the presence of
trimethylammoniumbromide, the transfer of MnO−4 is
The partition of a solute between two immiscible
solvents is governed by the distribution law. The ratio
International Journal of Chemical Kinetics DOI 10.1002/kin

PERMANGANATE TRANSFER AND REDUCTION BY D-GLUCOSE IN BENZENE–CTAB SOLUTION
499
Table II Effect of CTAB on the Pseudo-First-Order
of [solute] in the two phases will be constant and in-
dependent of the total quantity of solute. If a solute
may exist in different stages of aggregation in the two
systems, the law is valid only if the ratio of the concen-
trations of single molecules in the two phases is taken
into consideration. The analytical extractions are com-
plicated by association or dissociation processes that
occur in one or both of the solvents. To calculate the
partition coefficient of MnO−4 in benzene and aque-
ous media in different [CTAB], different sets of ex-
periments were performed under different conditions.
The values of partition coefficient of MnO−4 in the
benzene–aqueous media were found to be 9.8, 17.6,
and 37.9 × 10−3 at [CTAB] 4.0, 7.0, and 8.0 × 10−4
mol dm−3, respectively.
Rate Constants for the Oxidation of D-Glucose by MnO4−
at 30◦C
104 [CTAB]a
104k
104 [CTAB]
104k
(mol dm−3
)
(s−1obs
)
(mol dm−3
)
(s−1obs
)
0.0
4.0
6.0
8.0
0.0
3.8
5.1
6.6
10.0
12.0
16.0
20.0
7.0
7.6
7.5
7.3
a [D-glucose] = 2.0 × 10−3 mol dm−3, [MnO4−] = 2. 0 × 10−4
mol dm−3, and benzene = 40%.
from the slopes of the straight lines of the plots of
log(absorbance) versus time.
To see whether the MnO−4 ion was capable of re-
acting with CTAB under our kinetic conditions, the
same experiments were performed in the absence of D-
glucose (MnO−4 + CTAB). No decay in the absorbance
of MnO−4 was observed for the entire range of (CTAB)
used in the kinetic experiments. This suggests that there
was no oxidation of CTAB by MnO−4 .
A series of kinetic experiments were carried out in
the absence of externally added mineral acids (HClO4
and H2SO4); reduction of permanganate (2.0 × 10−4
mol dm−3) by D-glucose (2.0 × 10−3 mol dm−3) was
not observed under present experimental conditions.
Therefore, to see the effect of [CTAB] in the benzene–
water system, its concentration varied from 4.0 × 10−4
to 20.0 × 10−4 mol dm−3. The rate constant values are
summarized in Table II. Figure 2 shows the variation
of kobs with [CTAB]. The kobs had been found to in-
crease monotonically, and it became constant with the
increase in [CTAB]. The observed catalytic effect may,
The observation is not unexpected; aqueous sur-
factant solution has three components: surfactant
monomers in the aqueous solution, micellar aggre-
gates, and monomers absorbed as a film at the interface.
There is a dynamic equilibrium between aggregated
molecules and monomers. In surfactant solutions, mi-
celles form and break up so rapidly that both aggrega-
tion and dissociation of monomers occur at the same
time. Therefore, the partition coefficient of MnO−4 in
benzene and aqueous media cannot be constant. On
the other hand, it was observed that CTAB is insoluble
in benzene. Thus, we may safely conclude that the hy-
drophobic tails of CTAB aggregates may orient into the
benzene layer and polar head group remains in the wa-
ter phase in the benzene–water system. Benzene also
penetrates toward the hydrocarbon-like cores of CTAB
micelles, which are responsible for the solubilization
of benzene.
Reduction of MnO−4 by D-Glucose in the
CTAB–Benzene System
Preliminary observations showed that the transfer of
permanganate from the aqueous to the benzene phase
was slow at room temperature (30◦C). Therefore, the
choice of the best conditions for the evaluation of the
rate constant is a critical problem that we address first.
The requisite amounts of MnO−4 , CTAB, and benzene
were taken in a reaction vessel placed in a thermo-
stat at 30◦C for a sufficient time to transfer the max-
imum [MnO−4 ] from the aqueous to benzene phase.
The reaction was initiated with the addition of required
volume of the D-glucose solution. The zero time was
taken when half of the D-glucose solution had been
added. In the present study, it is necessary to point
out that the plot of log(absorbance) versus time de-
viates from linearity. It was noted that the extent of
deviation depended on the [D-glucose]. The values of
the rate constants of an initial stage were determined
Figure 2 Dependence of k on [CTAB]. Reaction condi-
obs
tions: MnO4− (2.0 × 10−4 mol dm−3), D-glucose (2.0 × 10−3
mol dm−3), benzene (40%), and temperature (30◦C).
International Journal of Chemical Kinetics DOI 10.1002/kin

500
MALIK AND KHAN
Table III Effect of [MnO−4 ], [D-glucose], and [H2SO4] on the Pseudo-First-Order Rate Constants at 30◦C
104 [MnO−4 ]a
103 [D-glucose]
105 [H2SO4]
104 k
obs
(mol dm−3
)
(mol dm−3
)
(mol dm−3
)
(s−1
)
(kobs–kcal)/k
obs
1.2
1.4
1.6
1.8
2.0
2.0
2.0
0.0
11.8
10.7
9.6
8.3
6.8
4.4 (3.7)b
5.7 (5.7)
6.8 (7.2)
9.4 (9.3)
11.0 (10.8)
4.2
1.0
1.6
2.0
2.6
3.0
2.0
0.0
+0.15
0.00
−0.05
+0.01
+0.01
2.0
3.7
5.6
3.8
7.4
2.8
9.3
1.5
11.2
1.1
a [CTAB] = 8.0 × 10−4 mol dm−3 and benzene = 40%.
b Calculated rate constants (Eq. (11)) are given in parentheses along with the kobs values.
therefore, be due to the (i) presence of free micelles and
(ii) micellization of reactants.
The effect of varying [MnO−4 ] on the re-
action rate was studied at constant D-glucose
(2.0 × 10−3 mol dm−3), temperature (30◦C), and
CTAB (8.0 × 10−4 mol dm−3). We observed Table
III that the kobs values decrease with the increase in
[MnO−4 ]. The basic trend in chemical kinetics is that
the pseudo-first-order rate constants are independent of
the initial concentration of the reactant in defect. The
same type of defect has earlier been observed in many
oxidation reactions of organic oxidants by perman-
ganate and especially in those having an autocatalytic
character [24]. Such type of behavior may be due to
flocculation of the colloidal particles of MnO2 [25].
The rate of the reaction can be represented by Eq. (1)
Figure 3 Dependence of k on D-glucose. Reaction con-
obs
ditions were the same as those mentioned in Fig. 2 with
ꢀ
ꢁ
CTAB (8.0 × 10−4 mol dm−3).
−d MnO−4
ꢀ
ꢁ
= kobs MnO−4
(1)
T
dt
Preliminary observations showed that a reaction
mixture containing CTAB and percholoric acid be-
came turbid, which increases with [HClO4]. There-
fore, H2SO4 was used to verify the role of [H+] on
the oxidation rate. The effect of [H+] was studied
as a function of [H2SO4] between 3.7 × 10−5 and
11.2 × 10−5 mol dm−3 at constant MnO−4 (2.0 × 10−4
mol dm−3), D-glucose (2.0 × 10−3 mol dm−3), CTAB
(8.0 × 10−4 mol dm−3), and temperature (30◦C). The
rate decreased with the increase in [H2SO4] (Table III).
In the presence of H2SO4, the inhibitory effect is due
to the exclusion of reactants from the reaction site (i.e.,
the Stern layer, as most of the ionic micelle mediated
Table III also contains pertinent data regard-
ing the reaction studied as a function of [D-
glucose] (1.0 × 10−3 to 3.0 × 10−3 mol dm−3) at
MnO−4 (2.0 × 10−4 mol dm−3), and CTAB (8.0 × 10−4
mol dm−3). The kobs values are shown graphically in
Fig. 3. By plotting log kobs versus log[D-glucose], a
straight line with slope ca. 1.0 was obtained, indicat-
ing the order to be 1 with respect to [D-glucose]. Thus,
the rate equation experimentally found was
ꢀ
ꢁ
−d MnO−4
ꢀ
ꢁ
= kobs MnO−4 T[D−glucose] (2)
dt
International Journal of Chemical Kinetics DOI 10.1002/kin

PERMANGANATE TRANSFER AND REDUCTION BY D-GLUCOSE IN BENZENE–CTAB SOLUTION
501
reactions are believed to occur in the region). As we in-
crease the [H2SO4], the [H+] will try to get associated
with the MnO−4 and will thus compete for a site (Stern
layer). Consequently, [reactant] is decreased from the
reaction site due to the exclusion effect.
To gain insight into the inhibitory role of [H2SO4],
the effect of [Na2SO4] was also investigated under
the same kinetic experimental conditions in the ab-
sence of H2SO4. The kobs values were found to be 6.6,
6.8, 6.7, and 6.8 10−4 s−1 at 105 [Na2SO4] of 3.7,
5.6, 7.4, 9.3, and 11.2 mol dm−3. These findings in-
dicate that the reaction rate remains the same in the
presence of SO42−. At higher [Na2SO4] (1.8 × 10−2 to
9.3 × 10−2 mol dm−3), kobs increases steeply by in-
creasing [Na2SO4] (kobs × 104 = 1.7, 2.4, 3.0, 3.6, and
4.3 s−1 at [Na2SO4] 1.8, 3.7, 5.5, 7.4, and 9.3 × 10−2
mol dm−3, respectively). Inert salts, especially the inor-
ganic ones, act as catalysts or inhibitors in the micelle-
mediated reactions [26]. It has also been established
that salts of high solubility in the aqueous phase can
also increase the binding constant of substrate to the
micelles by salting out the substrate from the aque-
ous pseudophase, and this results in enhancement of
the rate [27]. The catalysis of the reaction at higher
[Na2SO4] could be rationalized in terms of the salting
out effect.
To identify the nature of the intermediate(s), the
spectrum of the reaction mixture MnO−4 (2.0 × 10−4
mol dm−3), D-glucose (2.0 × 10−3 mol dm−3), and
CTAB (8.0 × 10−4 mol dm−3) was recorded at the end
of the reaction. The plot of log(absorbance) versus
log(wavelength) was linear (slope = −5.9; see Fig. 4).
The linear relationship between log(absorbance) and
log(wavelength) suggests that the soluble Mn(IV)
species is present in the form of colloidal particles of
MnO2 [28,29]. To substantiate the formation of Mn(III)
as an intermediate, the effect of adding sodium fluoride
Figure 4 Plot of log(absorbance) versus log(wavelength).
Reaction conditions were the same as those in Fig. 3.
was also investigated at constant MnO−4 (2.0 × 10−4
mol dm−3), D-glucose (2.0 × 10−3 mol dm−3), CTAB
(8.0 × 10−4 mol dm−3), and temperature (30◦C). The
values of kobs were found to be decrease with the in-
creasing amount of [F−] (kobs × 10−4 = 6.4, 6.2, 6.0,
5.7, 5.6, 5.4, and 5.2 s−1 at [F−] 0.0, 1.0, 2.0, 4.0, 6.0,
8.0, and 10.0 × 10−4 mol dm−3, respectively). The ob-
served inhibitory effect suggests the possibility of for-
mation of Mn(III). Therefore, it can be concluded that
Mn(IV) (colloidal in nature) and Mn(III) species are
formed as the intermediates in the reaction of MnO4−
by D-glucose in the presence of CTAB.
From these results, the most possible mechanism
for the reaction of MnO4− by D-glucose can be repre-
sented by Eqs. (1)–(7). Under our experimental condi-
tions, MnO−4 and β-D-glucopyronase are the predomi-
nant species in line with the argument presented else-
where [30, 31]. The mechanism is, therefore, given in
Scheme 1.
Scheme 1
International Journal of Chemical Kinetics DOI 10.1002/kin

502
MALIK AND KHAN
Table IV Effect of CTAB, Benzene, and Mineral Acids on the Reactivity of MnO−4 + D-Glucose Reaction
Reaction Conditionsa
104 k (s−1) Role of CTAB/Benzene/Mineral Acids Reference
obs
(1) MnO−4 + D-glucose
No reaction
No reaction
0.2
No reaction
6.8
1.1
Turbidity
Turbidity
[18]
(2) MnO−4 + D-glucose + CTAB
Present work
Present work
Present work
Present work
Present work
(3) MnO−4 + D-glucose + H2SO4
Catalysis
(4) MnO−4 + D-glucose + HClO4
(5) MnO−4 + D-glucose + CTAB + Benzene
(6) MnO−4 + D-glucose + CTAB + Benzene+H2SO4
(7) MnO−4 + D-glucose + CTAB + Benzene + HClO4
(8) CTAB + HClO4
Catalysis
Inhibition
18
[18]
a [MnO−4 ] = 2. 0 ×10−4 mol dm−3, [D-glucose] = 2.0 ×10−3 mol dm−3, [CTAB] = 8.0 × 10−4 mol dm−3, [H2SO4] = 1.12 × 10−4 mol dm−3
,
benzene = 40%, and temperature = 30◦C.
Other contributing steps are as follows:
in the solubilization and association of the reactant
species with the increase in the [CTAB] that reaches
a limiting value (Fig. 2). The catalysis of the reaction
could be rationalized in terms of the electrostatic effect.
Incorporation of MnO−4 and D-glucose into a limited
volume of CTAB micelles decreases the entropy loss
that is associated with bringing reactants together in
the transition state, leading to an increase in the rate
constants in the presence of the surfactant [23].
fast
Mn(IV) + β-D-Glucopyranose −→
Mn(II) + Lactone (6)
fast
Mn(IV) + Mn(II) −→ 2Mn(III)
(7)
fast
Mn(III) + β-D-Glucopyranose −→
Mn(II) + radical (8)
In micelle-mediated reactions, it is not possible to
precisely locate the exact site of the reaction, but re-
actants’ localization can be considered. It is observed
that MnO−4 forms an ion-pair complex with the pos-
itive head group of CTAB aggregates. On the other
hand, D-glucose is a neutral molecule and has no de-
gree of hydrophobicity due to the high solubility in
water. Therefore, its presence in the Stern layer cannot
be completely ruled out, thus packing the reactants in
a small volume and resulting in the observed catalysis.
Interestingly, the reactivity of D-glucose toward
MnO−4 in the presence of benzene is much higher than
its oxidation in the presence of CTAB only (Table IV).
Addition of benzene to the reaction mixture contain-
ing MnO−4 , D-glucose, and CTAB increases the reaction
rate significantly. The redox reaction probably occurs
at the interfacial region of the Gouy–Chapman and
Stern layer. In the presence of benzene, the possible
reaction site is at the water–hydrocarbon interface. To
see the role of anionic surfactant, attempts were made
to carry out the oxidation reaction in the presence of
SDS. Preliminary observations showed that the ben-
zene layer does not become purple in the presence of
SDS. The observation is not unexpected; the anionic
head group of SDS, simply based on electrostatic con-
siderations, will repel the MnO−4 , keeping the [MnO4−]
unaffected. On the other hand, SDS is unstable [19]
in the presence of acidic MnO−4 . Therefore, [H+] can-
not be used to neutralize the surface charge of SDS
micelles.
fast
radical + Mn(III) −→ Lactone + Mn(II) (9)
The complete rate law for the reaction is given by
ꢀ
ꢁ
−d MnO−4
ꢀ
ꢁ
= k MnO−4 T[D-glucose]
(10)
dt
where k represents the rate constants.
Considering Scheme 1, the rate law (10) can be
written as
kobs = Kck[D-glucose]
(11)
where k = Kck
ꢀ
ꢁ
−d MnO−4
ꢀ
ꢁ
= Kck MnO−4 [D-glucose]
(12)
dt
The derived rate law clearly accounts for the first-order
dependence on [D-glucose] in the absence of H2SO4.
The value of Kck obtained from the slope of Fig. 3 was
found to be 0.36 mol−1 dm3 s−1. The kcal values are cal-
culated by substituting the Kck and [D-glucose] values
in Eq. (11) and compared with kobs (Table III). A close
agreement between kobs and kcal provides a supporting
evidence for the mechanism shown in Scheme 1.
Now the kinetic results in the CTAB solution will
be considered. The increase in the rate constant with
the increase in [CTAB] may be due to the increase
International Journal of Chemical Kinetics DOI 10.1002/kin

PERMANGANATE TRANSFER AND REDUCTION BY D-GLUCOSE IN BENZENE–CTAB SOLUTION
503
The authors are very thankful to the reviewers for their helpful
suggestions and constructive comments.
16. Dar, M. Y.; Andrabi, S. M. Z.; Khan, Z. Colloid Polym
Sci 2006, 284, 1008.
17. Cordes, E. H.; Dunlap, R. B. Acc Chem Res 1969, 2,
329.
18. Andrabi, S. M. Z.; Malik, M. A.; Khan, Z. Colloids Surf
A Physicochem Eng Aspect 2007, 299, 58.
19. Raju; Khan, Z. Bull Chem Soc Jpn 2005, 78, 1218.
20. Sala, L. F.; Signorella, S. R.; Rizotto, M.; Frascaroli,
M. I.; Gandolfo, F. Can J Chem 1992, 70, 2046.
21. Sam, D. J.; Simmons, H. E. J Am Chem Soc 1972, 94,
4024.
BIBLIOGRAPHY
1. Starks, C. M. J Am Chem Soc 1971, 93, 195.
2. Menger, F. M. J Am Chem Soc 1970, 92, 5965.
3. Starks, C. M.; Owens, R. M. J Am Chem Soc 1973, 95,
3613.
4. Fendler, J. H.; Fendler, E. J. Catalysis in Micellar and
Macromolecular Systems; Academic Press: New York,
1975.
5. Herriott A. W.; Picker, D. Tetrahedron Lett 1974, 1511.
6. Burke, S.; Jarvie, A. W. P.; Gaines, A. F. Fuel 1990, 69,
1370.
22. Symons, M. C. R.; Traveleon, P. A. J Chem Soc 1962,
3503.
23. Gensmantel, N. P.; Page, M. I. J Chem Soc, Perkin II
1982, 147.
24. Wiberg, K. B.; Stewart, R. J Am Chem Soc 1955, 77,
1786.
7. Perez-Benito, J. F.; Arias, C. J Colloid Interface Sci
1992, 152, 70.
25. Perez-Benito, J. F.; Arias, C.; Amat, E. J. Colloid Inter-
face Sci 1996, 177, 288.
8. Nakamura, K.; Nishiyama, S.; Tsuruya, S.; Masai, M.
J Mol Catal 1994, 93, 195.
26. Tascioglu, S. Tetrahedron 1996, 52, 11113 and the ref-
erences cited therein.
9. Rankin, K. N.; Liu, Q.; Hendry, J.; Yee, H.; Noureldin,
N. A.; Lee, D. G. Tetrahedron Lett 1998, 39, 1095.
10. Seol, Y.; Schwartz, F. W. J Contam Hydrol 2000, 44,
185.
11. Reger, D. L.; Habib, M. M. J Mol Catal 1978, 4, 315.
12. Bunton, C. A.; Nome, F.; Romsted, L. S.; Quina, F. H.
Acc Chem Res 1991, 24, 357.
13. Cierpiszewski, R.; Hebrant, M.; Szymanowski, J.;
Tondre, C. J Chem Soc, Faraday Trans 1996, 92, 249.
14. Rodriguez, A.; Moya, M. L. Langmuir 1996, 12,
4090.
27. (a) Al-Lohedan, H. A.; Bunton, C. A.; Romsted, L. S.
J Phys Chem 1981, 85, 2123; (b) J Org Chem 1982, 47,
3528.
28. Lee, D. G.; Brown, K. C. J Am Chem Soc 1982, 104,
5076.
29. Freeman, F.; Fuselier, C. O.; Armstead, C. R.; Dalton,
C. E.; Davidson, P. A.; Karchefskui, E. M.; Krochman,
D. E.; Johnson, M. N.; Jones, N. K. J Am Chem Soc
1981, 103, 1154.
30. Kabir-ud-Din; Morshed, A. M. A.; Khan, Z. Carbohy-
drate Res 2002, 337, 1573.
15. Kabir-ud-Din, Hartani, K.; Khan, Z. Colloid Surf A
Physicochem Eng Aspect 2001, 193.
31. Kabir-ud-Din; Morshed, A. M. A.; Khan, Z. Int J Chem
Kinet 2003, 35, 543.
International Journal of Chemical Kinetics DOI 10.1002/kin