Kinetics and mechanism of oxidation of D-fructose and D-glucose by sodium salts of N-(chloro)-mono/di-substituted benzenesulfonamides in aqueous alkaline medium

Article abstract of DOI:10.1002/kin.20103

In an effort to introduce N-chloroarylsulfonamides of different oxidizing strengths, nine sodium salts of mono- and di-substituted N- chloroarylsulfonamides are employed as oxidants for studying the kinetics of oxidation of D-fructose and D-glucose in aqueous alkaline medium. The results are analyzed along with those by the sodium salts of N-chlorobenzenesulfonamide and N-chloro-4-methylbenzenesulfonamide. The reactions show first-order kinetics each in [oxidant], [Fru/Glu], and [OH^-]. The rates slightly increase with increase in ionic strength of the medium. Further, the rate of oxidation of fructose is higher by 4 to 5 times than that of the glucose oxidation, by the same oxidant. Similarly, E_a values for glucose oxidations are higher by about 1.5 times the E_a values for fructose oxidations. The results have been explained by a plausible mechanism, and the related rate law deduced. The significant changes in the kinetics and thermodynamic data are observed with change of substituent in the benzene ring. It is because Cl ⁺ is the effective oxidizing species in the reactions of N-chloroarylsulfonamides. The oxidative strengths of the latter therefore depend on the ease with which Cl⁺ is released from them. The ease with which Cl⁺ is released from N-chloroarylsulfonamides depends on the electron density of the nitrogen atom of the sulfonamide group, which in turn depends on the nature of the substituent in the benzene ring. The following Hammett equations are valid for the oxidation of fructose and glucose, log k_obs = -3.13 + 0.54 σ ρ and log k_obs = -3.81 + 0.28 σ ρ, respectively. The enthalpies and entropies of activations for oxidations by all the N-chloroarylsulfonamides correlate well with isokinetic temperatures of 301 K and 299 K, for fructose and glucose oxidations, respectively. The effect of substitution in the oxidants on the E_a and log A for the oxidations is also considered.

Full text of DOI:10.1002/kin.20103

Kinetics and Mechanism of
Oxidation of D-Fructose and
D-Glucose by Sodium Salts
of N-(Chloro)-mono/
di-substituted
Benzenesulfonamides in
Aqueous Alkaline Medium
B. THIMME GOWDA, N. DAMODARA, K. JYOTHI
Department of Post-Graduate Studies and Research in Chemistry, Mangalore University, Mangalagangothri 574 199,
Mangalore, India
Received 17 October 2004; accepted 31 March 2005
DOI 10.1002/kin.20103
Published online in Wiley InterScience (www.interscience.wiley.com).
ABSTRACT: In an effort to introduce N-chloroarylsulfonamides of different oxidizing strengths,
nine sodium salts of mono- and di-substituted N-chloroarylsulfonamides are employed as
oxidants for studying the kinetics of oxidation of D-fructose and D-glucose in aqueous
alkaline medium. The results are analyzed along with those by the sodium salts of N-
chlorobenzenesulfonamide and N-chloro-4-methylbenzenesulfonamide. The reactions show
−
first-order kinetics each in [oxidant], [Fru/Glu], and [OH ]. The rates slightly increase with
increase in ionic strength of the medium. Further, the rate of oxidation of fructose is higher
by 4 to 5 times than that of the glucose oxidation, by the same oxidant. Similarly, Ea val-
ues for glucose oxidations are higher by about 1.5 times the Ea values for fructose oxida-
tions. The results have been explained by a plausible mechanism, and the related rate law
deduced. The significant changes in the kinetics and thermodynamic data are observed with
+
change of substituent in the benzene ring. It is because Cl is the effective oxidizing species in
the reactions of N-chloroarylsulfonamides. The oxidative strengths of the latter therefore de-
+
+
pend on the ease with which Cl is released from them. The ease with which Cl is released
from N-chloroarylsulfonamides depends on the electron density of the nitrogen atom of the
Correspondence to: B. Thimme Gowda; e-mail: gowdabt@
yahoo.com.
ꢀ
c 2005 Wiley Periodicals, Inc.

KINETICS AND MECHANISM OF OXIDATION OF D-FRUCTOSE AND D-GLUCOSE
573
sulfonamide group, which in turn depends on the nature of the substituent in the benzene ring.
The following Hammett equations are valid for the oxidation of fructose and glucose, log kobs
=
–
3.13 + 0.54 σ p and log k
= −3.81 + 0.28 σ p, respectively. The enthalpies and entropies of
obs
activations for oxidations by all the N-chloroarylsulfonamides correlate well with isokinetic
temperatures of 301 K and 299 K, for fructose and glucose oxidations, respectively. The effect of
substitution in the oxidants on the Ea and log A for the oxidations is also considered. ꢀC 2005
Wiley Periodicals, Inc. Int J Chem Kinet 37: 572–582, 2005
INTRODUCTION
zenesulfonamide, NC4BBS) and i-X-j-Y-C6H3SO2-
NaNCl·xH2O, where i-X-j-Y = 2,3-(CH3)2 (N-choro-
2,3-dimethylbenzenesulfonamide, NC23DMBS); 2,4-
(CH ) (N -choro-2,4-dimethylbenzenesulfonamide,
N-Haloarylsulfonamides have received considerable
attention due to their diverse properties [1–11]. They
act as halonium cations, hypohalite species, and N-
anions that behave both as bases and nucleophiles.
Although the various aspects of two members of this
class of reagents, the sodium salts of N-chlorobenzen-
esulfonamide (chloramine-B, NCBS) and N-chloro-4-
methylbenzenesulfonamide (chloramine-T, NC4MBS)
have been studied, there are no efforts in altering the
electron environment around sulfonamide group to get
3
2
NC24DMBS); 2-CH -4-Cl (N-chloro-2-methyl-4-
3
chlorobenzenesulfonamide, NC2M4CBS); 2,4-Cl2
(N-chloro-2,4-dichlorobenzenesulfonamide, NC24D
CBS) and 3,4-Cl (N-chloro-3,4-dichlorobenzenesul-
2
fonamide, NC34DCBS).
MATERIALS AND METHODS
+
Cl released either at ease or with difficulty, by mak-
ing appropriate substitution in the benzene ring to pro-
duce N-chloroarylsulfonamide of required oxidizing
strength for a specific purpose. Hence in an effort to in-
troduce N-chloroarylsulfonamides of varying oxidiz-
ing strengths, we have recently reported several sodium
salts of N-chloro-mono/di-substituted benzenesulfon-
amides (NCSBS) as oxidants [10–15].
Preparation of Arylsulfonamides and Sodium Salts
of N-chloroarylsulfonamides. The nine sodium salts
of N-chloroarylsulfonamides, NC4EBS, NC4FBS,
NC4CBS, NC4BBS, NC23DMBS, NC24DMBS,
NC2M4CBS, NC24DCBS, and NC34DCBS, were
prepared in two steps [12,13]. In the first step, the
substituted benzenes were chlorosulfonated with
chlorosulfonic acid to the corresponding sulfonylchlo-
rides and the latter were converted into the respective
substituted benzenesulfonamides, by boiling them
with concentrated ammonium hydroxide. The result-
ing arylsulfonamides were recrystallized to constant
melting points from diluted ethanol and dried at
Carbohydrates comprise one of the largest classes
ofbiologicallyimportantcompoundsandarecharacter-
izedbythepresenceofanaldehydicorketoniccarbonyl
group [16,17]. The monosaccharides such as glucose
and fructose have wide synthetic applications. Glucose
is a source of energy in plants and animals and also
serves as the monomeric unit of cellulose, the struc-
tural framework in woody plants. Hence the reactions
involving carbohydrates are of considerable interest.
Although oxidation of carbohydrates by chloramine-B
and chloramine-T has been studied [18,19], individu-
ally, there are no reports on the systematic oxidation
of carbohydrates by substituted N-chloro-substituted
benzenesulfonamides. We report herein the kinetics of
oxidation of D-fructose and D-glucose by nine sodium
salts of N-chloro-substituted benzenesulfonamides in
aqueous alkaline medium and analyze the results with
those by NCBS and NC4MBS. The sodium salts of
mono- and di-substituted N-chlorobenzenesulfona-
mides (NCSBS) employed as oxidants are of the
general formulae: i-X-C6H4SO2NaNCl · xH2O, where
i-X=4-C2H5 (N-chloro-4-ethylbenzene-sulfonamide,
NC4EBS); 4-F (N-chloro-4-fluorobenzenesulfona-
mide, NC4FBS); 4-Cl (N-chloro-4-chlorobenzenesul-
fonamide, NC4 CBS) or 4-Br (N-chloro-4-bromoben-
◦
105 C [12,13]. The arylsulfonamides were then
N-chlorinated by bubbling pure chlorine gas through
clear aqueous solutions of them in 4 M NaOH at
◦
70 C for about 1 h. The precipitated sodium salts of
N-chloro-substituted benzenesulfonamides (NCSBS)
were filtered, washed, dried, and recrystallized from
water. The purity of all the reagents was checked by
determining the melting points [12,13] and by esti-
mating iodometrically, the amounts of active chlorine
which they contained. All the arylsulfonamides and
their N-chloro compounds were further characterized
by recording their infrared spectra.
Aqueous stock solutions (0.1 mol dm−3) of N-
chloroarylsulfonamides were prepared in doubly dis-
tilled water and stored in amber-colored bottles.
The solutions were standardized by the iodometric
method. Fresh solutions of D-fructose and D-glucose
−
3
(E. Merck) in doubly distilled water (0.10 mol dm
)
were prepared as and when required. Ionic strength

574
GOWDA, DAMODARA, AND JYOTHI
−
3
−
−
of the medium was maintained at 0.50 mol dm
using concentrated aqueous solution of sodium nitrate
E. Merck). All other reagents employed were of ana-
C6H12O6 + 2ArSO2NCl + 3OH
−
−
→
C4H8O5 + CH2(OH)COO + 2ArSO2NH
(
(
Erythronic acid)
lytical grades of purity.
−
+
2Cl + H2O
(2)
−
−
RESULTS AND DISCUSSION
C6H12O6 + 3ArSO2NCl + 5OH
−
−
→
C3H6O4 + CH2(OH)COO + HCOO
Stoichiometry and Product Analysis
Glyceric acid
The reaction mixture containing the carbohydrate,
NaOH, and excess of NCSBS was equilibrated for 48 h.
Excess oxidant was then determined iodometrically.
Varying stoichiometries were observed corresponding
to the formation of a mixture of products as shown
by the following stoichiometric equations. The major
productsofoxidationwerearabinonic, ribonic, andery-
thronic acids. The minor products were glyceric and
hexonic acids. The mechanism of formation of these
products will be given later.
−
−
+
3ArSO2NH + 3Cl + 2H2O
(3)
(4)
−
−
C6H12O6 + ArSO2NCl + OH
−
−
→
C6H12O7 + ArSO2NH + Cl
Hexonic acid
where Ar = C6H5, 4-CH3C6H4, 4-C2H5C6H4, 4-
FC6H4, 4-ClC6H4, 4-BrC6H4, 2,3-(CH3)2C6H3, 2,4-
(
3
CH3)2C6H3, 2-CH3-4-ClC6H3, 2,4-Cl2C6H3, and
,4-Cl2C6H3.
The reduction products, arylsulfonamides
ArSO2NH2, SBSA), were identified by TLC [20]
using petroleum ether–chloroform–butanol (2:2:1 v/v)
as the solvent system and iodine as spray reagent.
C6H12O6 + ArSO2NCl + H2O + OH−
−
(
−
−
→
C5H10O6 + CH2(OH)2 + ArSO2NH + Cl
(
Arabinonic or ribonic acids)
(1)
Table I Pseudo-First-Order Rate Constants (kobs) for the Oxidation of D-Fructose (Fru) by the Sodium Salts of
N-chloro-para-substituted Benzenesulfonamides (NCSBS) in Aqueous Alkaline Medium at 303 K (I = 0.5 mol dm
Except During Its Variation)
−
3
1
04kobs (s−1) i-X-C6H4SO2(Na)NCl·xH2O, X =
3
2
1
(
0 [NCSBS]0
10 [Fru]0
10[NaOH]
−
3
−3
−3
mol dm
)
(mol dm
)
(mol dm
)
Parent
4-CH3
4-C2H5
4-F
4-Cl
4-Br
Effect of varying [NCSBS]0
0
1
2
4
.5
.0
.0
.0
2.0
2.0
2.0
2.0
1.0
1.0
1.0
1.0
9.6
9.6
9.4
9.5
7.4
7.5
7.4
7.1
7.7
7.7
7.5
7.4
10.9
10.8
10.9
10.9
12.3
12.4
12.4
12.6
12.2
12.1
12.3
12.4
Effect of varying [Fru]0
1
1
1
1
1
.0
.0
.0
.0
.0
0.5
1.0
2.0
3.0
5.0
1.0
1.0
1.0
1.0
1.0
2.5
3.6
9.6
12.5
20.3
1.2
3.2
7.5
10.3
17.2
1.5
3.1
7.7
10.9
16.7
1.9
4.7
10.8
14.5
23.4
1.0
5.4
12.4
18.6
34.6
2.4
5.8
12.1
21.0
32.8
Effect of varying [NaOH]
1
1
1
1
1
.0
.0
.0
.0
.0
2.0
2.0
2.0
2.0
2.0
0.3
0.5
1.0
2.0
3.0
3.0
4.0
9.6
22.0
30.2
1.4
2.9
7.5
14.9
24.0
1.2
2.6
7.7
18.1
27.9
1.8
4.3
10.8
24.8
30.6
2.2
4.8
12.4
28.1
35.0
2.2
5.2
12.1
25.3
41.8
Effect of varying ionic strength
a
1.0
1.0
1.0
2.0
2.0
2.0
1.0
1.0
1.0
8.4
9.6
10.0
6.7
7.5
8.4
5.9
7.7
8.3
8.7
10.8
11.5
10.9
12.4
12.8
10.0
12.1
14.7
b
a
b
−3
−3
I = 0.30 mol dm
I = 0.70 mol dm
.
.

KINETICS AND MECHANISM OF OXIDATION OF D-FRUCTOSE AND D-GLUCOSE
575
Table II Pseudo-First-Order Rate Constants (kobs) for the Oxidation of D-Fructose (Fru) by the Sodium Salts of
−
3
N-chloro-di-substituted Benzenesulfonamides (NCSBS) in Aqueous Alkaline Medium at 303 K (I = 0.5 mol dm
Except During Its Variation)
1
04kobs (s−1) i-X, j-Y-C6H3SO2(Na)NCl·xH2O, i-X, j-Y =
3
2
1
(
0 [NCSBS]0
10 [Fru]0
10[NaOH]
−
3
−3
−3
mol dm
)
(mol dm
)
(mol dm
)
2,3-(CH3)2
2,4-(CH3)2
2-CH3,4-Cl
2,4-Cl2
3,4-Cl2
Effect of varying [NCSBS]0
0
1
2
4
.5
.0
.0
.0
2.0
2.0
2.0
2.0
1.0
1.0
1.0
1.0
5.8
5.8
5.8
5.9
7.2
7.7
7.8
8.5
9.9
9.8
9.8
20.2
20.0
20.1
20.1
16.7
16.1
16.2
16.1
10.0
Effect of varying [Fru]0
1
1
1
1
1
.0
.0
.0
.0
.0
0.5
1.0
2.0
3.0
5.0
1.0
1.0
1.0
1.0
1.0
0.9
2.4
5.8
10.5
19.1
1.0
2.9
7.7
10.9
14.9
1.8
4.2
9.8
13.7
20.4
4.5
8.4
20.0
27.1
39.2
3.2
6.7
16.1
29.6
35.6
Effect of varying [NaOH]
1
1
1
1
1
.0
.0
.0
.0
.0
2.0
2.0
2.0
2.0
2.0
0.3
0.5
1.0
2.0
3.0
0.7
1.8
5.8
12.3
20.0
1.1
2.7
7.7
17.9
23.6
1.8
4.0
9.8
19.4
30.2
4.9
7.2
20.0
37.7
54.7
3.0
6.7
16.1
34.6
44.8
Effect of varying ionic strength
a
1.0
1.0
1.0
2.0
2.0
2.0
1.0
1.0
1.0
4.8
5.8
6.8
5.8
7.7
7.8
8.0
9.8
11.9
16.8
20.0
22.9
14.0
16.1
16.8
b
a
b
−3
−3
I = 0.30 mol dm
I = 0.70 mol dm
.
.
3
3
Figure 1 Plots of kobs versus [Fru]0; 10 [NCSBS]0 =
Figure 2 Plots of kobs versus [Glu]0; 10 [NCSBS]0 =
−3
−3
1
0[NaOH] = 2I = 1.0 mol dm , temperature 303 K.
10[NaOH] = 2I = 1.0 mol dm , temperature 303 K.
NCSBS : i-X-C6H4SO2NaNCl, where X = 4-H, 4-CH3,
NCSBS : i-X-C6H4SO2NaNCl, where X = 4-H, 4-CH3, 4-F
or 4-Cl and i-X-j-Y-C6H3SO2NaNCl, where i-X-j-Y = 2,4-
(CH3)2, 2-CH3-4-Cl or 2,4-Cl2.
4
-F, or 4-Cl and i-X-j-Y-C6H3SO2NaNCl, where i-X-j-Y =
2
,4-(CH3)2, 2-CH3-4-Cl, or 2,4-Cl2.

576
GOWDA, DAMODARA, AND JYOTHI
Table III Pseudo-First-Order Rate Constants (kobs) for the Oxidation of D-Glucose (Glu) by the Sodium Salts of
N-chloro-para-substituted Benzenesulfonamides (NCSBS) in Aqueous Alkaline Medium at 303 K (I = 0.5 mol dm
Except During Its Variation)
−
3
1
04kobs (s−1) i-X-C6H4SO2(Na)NCl·xH2O, X =
3
2
1
(
0 [NCSBS]0
10 [Glu]0
10[NaOH]
−
3
−3
−3
mol dm
)
(mol dm
)
(mol dm
)
Parent
4-CH3
4-C2 H5
4-F
4-Cl
4-Br
Effect of varying [NCSBS]0
0
1
2
4
.5
.0
.0
.0
2.0
2.0
2.0
2.0
1.0
1.0
1.0
1.0
1.8
1.8
1.7
1.7
1.6
1.7
1.6
1.6
2.4
2.4
2.1
2.1
2.1
2.1
2.2
2.1
2.4
2.4
2.4
2.4
2.2
2.2
2.1
2.1
Effect of varying [Glu]0
1
1
1
1
1
.0
.0
.0
.0
.0
0.5
1.0
2.0
3.0
5.0
1.0
1.0
1.0
1.0
1.0
0.5
1.0
1.8
2.2
4.1
0.5
0.9
1.7
2.5
4.1
0.5
0.8
2.4
3.4
6.4
0.5
1.1
2.1
3.3
5.3
0.6
1.1
2.4
3.8
6.5
0.7
1.3
2.2
5.7
8.2
Effect of varying [NaOH]
1
1
1
1
1
.0
.0
.0
.0
.0
2.0
2.0
2.0
2.0
2.0
0.3
0.5
1.0
2.0
3.0
0.3
0.7
1.8
3.3
6.3
0.4
0.7
1.7
4.7
6.1
0.3
1.0
2.4
3.9
5.6
0.4
0.8
2.1
5.0
8.9
0.5
0.9
2.4
6.5
11.3
0.3
1.0
2.2
7.7
10.2
Effect of varying ionic strength
a
1.0
1.0
1.0
2.0
2.0
2.0
1.0
1.0
1.0
1.4
1.8
2.1
1.3
1.7
2.0
1.8
2.4
2.7
1.7
2.1
2.6
2.1
2.4
2.8
1.8
2.2
2.9
b
a
b
−3
−3
I = 0.30 mol dm
I = 0.70 mol dm
.
.
Figure 3 (i) Plot of log kobs versus ꢀp (for Fru oxidation);
Figure 4 (i) Plot of log kobs versus ꢀp (for Glu oxidation);
3
3
1
0 [NCSBS]0 = 50[Fru]0 = 10[NaOH] = 2I = 1.0 mol
10 [NCSBS]0 = 50 [Glu]0 = 10[NaOH] = 2I = 1.0 mol
−3
−3
dm , temperature 303 K. NCSBS : i-X-C6H4SO2NaNCl,
dm , temperature 303 K. NCSBS : i-X-C6H4SO2NaNCl,
where X = 4-H, 4-CH3, 4-C2H5, 4-F, 4-Cl, or 4-Br. (ii) Plot of
where X = 4-H, 4-CH3, 4-C2H5, 4-F, 4-Cl, or 4-Br. (ii) Plot of
ꢁ=
ꢁ=
ꢁ
ꢁ=
ꢀ
H
versus ꢀS (for Fru oxidation) i-X-C6H4SO2NaNCl,
ꢀH versus ꢀS (for Glu oxidation) i-X-C6H4SO2NaNCl,
where i-X = 4-H, 4-CH3, 4-C2H5, 4-F, 4-Cl, or 4-Br and
i-X-j-Y-C6H3SO2NaNCl, where i-X-j-Y = 2,3-(CH3)2, 2,4-
(CH3)2, 2-CH3-4-Cl, 2,4-Cl2, or 3,4-Cl2.
where i-X = 4-H, 4-CH3, 4-C2H5, 4-F, 4-Cl, or 4-Br and
i-X-j-Y-C6H3SO2NaNCl, where i-X-j-Y = 2,3-(CH3)2, 2,4-
(CH3)2, 2-CH3-4-Cl, 2,4-Cl2, or 3,4-Cl2.

KINETICS AND MECHANISM OF OXIDATION OF D-FRUCTOSE AND D-GLUCOSE
577
Table IV Pseudo-First-Order Rate Constants (kobs) for the Oxidation of D-Glucose (Glu) by the Sodium Salts of
−
3
N-chloro-di-substituted Benzenesulfonamides (NCSBS) in Aqueous Alkaline Medium at 303 K (I = 0.5 mol dm
Except During Its Variation)
1
04kobs (s−1) i-X, j-Y-C6H3SO2(Na)NCl·xH2O, i-X, j-Y =
3
2
1
(
0 [NCSBS]0
10 [Glu]0
10[NaOH]
−
3
−3
−3
mol dm
)
(mol dm
)
(mol dm
)
2,3-(CH3)2
2,4-(CH3)2
2-CH3,4-Cl
2,4-Cl2
3,4-Cl2
Effect of varying [NCSBS]0
0
1
2
4
.5
.0
.0
.0
2.0
2.0
2.0
2.0
1.0
1.0
1.0
1.0
1.7
1.7
1.7
1.8
1.8
1.8
1.8
1.7
2.4
2.4
2.4
2.0
4.2
4.1
4.0
3.7
3.5
3.5
3.4
3.4
Effect of varying [Glu]0
1
1
1
1
1
.0
.0
.0
.0
.0
0.5
1.0
2.0
3.0
5.0
1.0
1.0
1.0
1.0
1.0
0.4
0.8
1.7
2.2
3.0
0.4
0.8
1.8
2.3
3.8
0.7
1.4
2.4
3.8
4.7
0.9
1.7
4.1
5.5
9.7
0.6
1.2
3.4
5.6
7.4
Effect of varying [NaOH]
1
1
1
1
1
.0
.0
.0
.0
.0
2.0
2.0
2.0
2.0
2.0
0.3
0.5
1.0
2.0
3.0
0.2
0.6
1.7
5.3
8.7
0.2
0.7
1.8
3.4
5.2
0.2
0.5
2.4
8.2
11.2
0.5
1.7
4.1
11.2
17.2
0.9
1.5
3.4
6.3
10.4
Effect of varying ionic strength
a
1.0
1.0
1.0
2.0
2.0
2.0
1.0
1.0
1.0
1.3
1.7
2.2
1.3
1.8
2.4
2.1
2.4
2.9
3.8
4.1
4.4
2.9
3.4
4.1
b
a
b
−3
−3
I = 0.30 mol dm
I = 0.70 mol dm
.
.
The Rf values of the reduced arylsulfonamides com-
pared with the values of the corresponding pure
arylsulfonamides are C6H5: 0.89 (0.88), 4-CH3C6H4:
at least two half-lives by the iodometric determination
of unreacted oxidant at regular intervals of time. The
pseudo-first-order rate constants (kobs) were computed
by the graphical methods, and the values were repro-
ducible within ± 4% error.
0
(
2
(
.92 (0.91), 4-C2H5C6H4: 0.93 (0.94), 4-FC6H4: 0.90
0.92), 4-ClC6H4: 0.91(0.93), 4-BrC6H4: 0.88 (0.89),
,3-(CH3)2C6H3: 0.91 (0.92), 2,4-(CH3)2C6H3: 0.96
0.96), 2-CH3-4-ClC6H3: 0.95 (0.96), 2,4-Cl2C6H3:
.93 (0.92), and 3,4-Cl2C6H3: 0.93 (0.94) sulfon-
The kinetic data on the oxidation of D-fructose
and D-glucose by NC4EBS, NC4FBS, NC4CBS,
NC4BBS, NC23DMBS, NC24DMBS, NC2M4CBS,
NC24DCBS, and NC34DCBS in aqueous alkaline
medium under varying conditions of [NCSBS], [Fru
or Glu], [NaOH], and ionic strength of the medium
are shown in Tables I–IV and Figs. 1–4. At constant
0
amides, respectively (values in parenthesis are for the
pure arylsulfonamides).
Kinetic Measurements
[Fru or Glu]0 (5–50-fold excess over [NCSBS]0) and
The kinetic studies were made in glass-stoppered
pyrex boiling tubes under pseudo-first-order con-
ditions with [Fru or Glu] ꢂ [NCSBS] (by 5–
[NaOH], the plots of log[NCSBS] versus time were lin-
ear up to at least 75% completion of the reactions. The
pseudo-first-order rate constants computed from the
plots remained unaffected by the changes in [NCSBS]
(Tables I–IV), establishing first-order dependence of
the rate on [NCSBS] for the oxidation of both the
substrates by all the reagents. At constant [NCSBS]0
and [NaOH], the rates increased with increase in [Fru
or Glu]0 with first-order dependences in all the cases
(Tables I–IV). The plots of kobs versus [Fru or Glu]0
gave straight lines passing through the origin (Figs. 1
5
0 times). The reactions were initiated by the rapid ad-
dition of known amounts of oxidant solution (0.0005–
−3
0
.004 mol dm ), pre-equilibrated at a desired tem-
perature, to mixtures containing the required amounts
−
3
of substrates (0.005–0.05 mol dm ), sodium hydrox-
−3
ide (0.03–0.30 mol dm ), sodium nitrate and water
in the boiling tube, thermostated at the same tempera-
ture. The progress of the reactions was monitored for

578
GOWDA, DAMODARA, AND JYOTHI
and 2). At constant [NCSBS]0 and [Fru or Glu]0, the
rates increased with increase in [OH ] with first-order
(CH3)2C6H3, 2,4-(CH3)2C6H3, 2-CH3,4-ClC6H3, 2,4-
Cl2C6H3, and 3,4-Cl2C6H3).
−
dependences on [NaOH] (Tables I–IV) for all the ox-
idations. At constant [NCSBS]0, [Fru or Glu]0, and
−
−
ArSO2NCl + H2O ꢁꢀ ArSO2NH2 + OCl
(5)
[NaOH], the rates increased with increase in the ionic
−
−
strength of the medium (Tables I–IV), indicating the in-
teraction of similar ions in the rate-determining steps.
The rates were measured at different temperatures for
the oxidation of both the substrates by all the oxi-
dants, and the activation parameters have been com-
puted from the Arrhenius and Eyring plots (Tables V
and VI).
ArSO2NCl + H2O ꢁꢀ ArSO2NHCl + HO (6)
ArSO2NHCl + HO− ꢁꢀ ArSO2NH2 + OCl− (7)
Equations (5) and (7) predict retardation of rates by
the reaction products, arylsulfonamides, while Eq. (6)
expects retardation of rates by OH ions. Since the rate
−
−
The sodium salts of N-chloroarylsulfonamides
increases with increase in OH and is not affected by
(
NCSBS) are fairly strong electrolytes in aqueous so-
the addition of sulfonamides, it is likely that the anion
ArSO2NCl is the active oxidant species.
−
lution [1,3]. They furnish different reactive species
depending on pH of the medium. The possible ox-
idizing species in alkaline solutions of NCSBS are
In alkaline solutions, sugars undergo isomerization
to an equilibrium mixture of aldoses and ketoses which
−
−
−
ArSO2NCl , ArSO2NHCl, OCl , andArSO2NCl2, de-
exist as enediol anions (E ) [21]. In the presence of
−
−
pending on [OH ] (where Ar = C6H5; 4-CH3C6H4,
oxidants, enolic anions react with ArSO2NCl to form
4
-C2H5C6H4, 4-FC6H4, 4-ClC6H4, 4-BrC6H4, 2,3-
intermediates, which subsequently undergo cleavages
Table V Activation Parameters for the Oxidation of D-Fructose by Sodium Salts of N-chloro-para- and di-substituted
Benzenesulfonamides (NCSBS) in Aqueous Alkaline Medium
i-X-C6H4SO2(Na)NCl·xH2O, X =
Parameters
Parent
4-CH3
4-C2H5
4-F
4-Cl
4-Br
Ea (kJ mol 1)
−
73.9
9.7
72.6
90.6
12.5
93.6
+4.0
92.4
73.4
9.5
78.9
81.9
11.2
81.1
79.2
10.8
83.6
72.2
9.5
71.6
log A
ꢁ
=
−1
ꢀ
ꢀ
ꢀ
H
(kJ mol
)
ꢁ
=
−1
−1
S
G
(J K mol
)
−63.2
−44.4
−34.3
−25.0
−64.5
ꢁ=
−1
(kJ mol
)
91.8
92.4
91.5
91.2
91.2
Optimized values with reference to log A value of the parent oxidant
Ea (kJ mol 1)
−
73.8
71.3
74.4
71.9
74.3
71.8
73.5
71.0
73.1
70.6
73.2
70.7
ꢁ
=
−1
ꢀ
H
(kJ mol )
Optimized values with reference to Ea value of the parent oxidant
log A
9.7
−67.7
9.6
−69.6
9.6
−69.6
9.8
−65.8
9.8
−65.8
9.8
−65.8
ꢁ
=
−1
−1
ꢀ
S
(J K mol
)
i-X-j-Y-C6H3SO2(Na)NCl·xH2O, i-X-j-Y =
Parent
2,3-(CH3)2
2,4-(CH3)2
2-CH3-4-Cl
2,4-Cl2
3,4-Cl2
Ea (kJ mol 1)
−
73.9
9.7
72.6
83.6
11.2
83.9
75.8
10.0
79.2
75.4
10.0
76.6
80.9
11.2
84.0
72.1
9.7
74.3
log A
ꢁ
=
−1
ꢀ
ꢀ
ꢀ
H
(kJ mol
)
ꢁ
=
−1
−1
S
G
(J K mol
)
−63.2
−30.1
−43.2
−49.9
−21.3
−51.4
ꢁ=
−1
(kJ mol
)
91.8
93.0
92.3
91.7
90.5
90.0
Optimized values with reference to log A value of the parent oxidant
Ea (kJ mol 1)
ꢀ
−
73.8
71.3
75.1
72.6
74.3
71.8
73.7
71.2
71.9
69.4
72.5
70.0
ꢁ
=
−1
)
H (kJ mol
Optimized values with reference to Ea value of the parent oxidant
log A
9.7
−67.7
9.5
−71.5
9.6
−69.6
9.7
−67.7
10.0
−61.9
9.9
−63.9
ꢁ
=
−
−1
ꢀ
S
(J K 1mol )

KINETICS AND MECHANISM OF OXIDATION OF D-FRUCTOSE AND D-GLUCOSE
579
Table VI Activation Parameters for the Oxidation of D-Glucose by Sodium Salts of N-chloro-para- and di-substituted
Benzenesulfonamides in Aqueous Alkaline Medium
i-X-C6H4SO2(Na)NCl · xH2O, X =
Parameters
Parent
4-CH3
4-C2H5
4-F
4-Cl
4-Br
Ea (kJ mol 1)
−
113.7
15.9
115.6
+64.5
96.1
113.7
15.8
114.2
+59.6
96.1
117.1
16.6
117.8
+74.5
95.2
95.7
134.3
19.5
134.7
+130.1
95.3
102.5
14.0
102.4
+22.7
95.5
log A
12.8
100.2
+15.0
95.6
ꢁ
=
−1
ꢀ
ꢀ
ꢀ
H
S
G
(kJ mol
)
ꢁ
=
−1
−1
(J K mol
)
)
ꢁ
=
−1
(kJ mol
)
Optimized values with reference to log A value of the parent oxidant
Ea (kJ mol 1)
−
113.9
111.4
114.1
111.6
113.2
110.7
113.6
111.1
113.2
110.7
113.5
111.0
ꢁ=
−1
ꢀ
H
(kJ mol )
Optimized values with reference to Ea value of the parent oxidant
log A
15.9
+51.0
15.8
+49.1
16.0
+53.0
15.9
+51.0
16.0
+53.0
15.9
+51.0
ꢁ=
−1
−1
ꢀ
S
(J K mol
i-X-j-Y-C6H3SO2(Na)NCl · xH2O, i-X-j-Y =
Parent
2,3-(CH3)2
2,4-(CH3)2
2-CH3-4-Cl
2,4-Cl2
3,4-Cl2
Ea (kJ mol 1)
−
113.7
15.9
115.6
+64.5
96.1
138.7
20.1
140.1
+145.4
96.0
128.3
18.4
127.2
+103.2
95.9
114.8
16.2
116.4
+69.8
95.3
133.6
19.6
135.6
+137.5
94.0
122.0
17.6
125.3
+102.1
94.4
log A
ꢁ
=
−1
ꢀ
ꢀ
ꢀ
H
S
G
(kJ mol
)
ꢁ
=
−1
−1
(J K mol
)
)
ꢁ
=
−1
(kJ mol
)
Optimized values with reference to log A value of the parent oxidant
Ea (kJ mol 1)
−
113.9
111.4
114.1
111.6
113.9
111.4
113.2
110.7
112.4
109.9
111.9
109.4
ꢁ=
−1
)
ꢀ
H (kJ mol
Optimized values with reference to Ea value of the parent oxidant
log A
15.9
+51.0
15.8
+49.1
15.9
+51.0
16.0
+53.0
16.1
+54.9
16.2
+56.8
ꢁ=
−1
−1
ꢀ
S
(J K mol
to give the products. The hexoses react with the oxi-
dantsthroughketo-enolicanionintermediates, andthey
react very slowly in the aldo-enolic forms. The ob-
served negative and positive entropies of activations
for D-fructose and D-glucose indicate that fructose has
more orderly structure than glucose. It is thus steri-
cally favored for oxidation by the oxidants. Hence it
is probable that in the case of glucose, the fructose
isomer formed by the alkali-catalyzed isomerization
reacts with the oxidants. This observation is supported
by the fact that the rates with fructose are higher by
are explained by the reaction sequences shown in
Scheme 1.
The rate law in accordance with Scheme 1 is given
by
Rate = −d[NCSBS]/dt
−
=
K1k2[S][OH ][NCSBS]/[H2O]
(8)
4
–5 times than those with glucose for the same oxi-
dant. Similarly Ea values are higher by about 1.5 times
with glucose compared to Ea values for fructose. In
other words, higher rates and lower Ea with fructose
and lower rates and higher Ea with glucose support
these observations.
Based on these facts, the kinetics of first order each
−
in [NCSBS], [S], and [OH ], positive ionic strength
and negligible product effects observed in the oxi-
dation of the substrates by N-chloroarylsulfonamides
Scheme 1

580
GOWDA, DAMODARA, AND JYOTHI
or
ing relations were found to be valid:
−
kobs = K1k2[S][OH ]/[H2O]
log kobs = −3.13 + 0.54 σ p
log kobs = −3.81 + 0.28 σ p
1
−
1
=
K k2[S][OH ], K = K1/[H2O]
(9)
1
1
Applicability of Hammett equation [22] has also
The enthalpies and the free energies of activations
for the oxidations of D-fructose and D-glucose by all
the N-chloroarylsulfonamides have been correlated.
been tested for the oxidation of both fructose and glu-
cose by all the oxidants. The plots of log kobs versus σp
were reasonably linear (Figs. 3 and 4), and the follow-
ꢁ
ꢁ=
The plots of ꢀH versus ꢀS (Figs. 3 and 4) were
Scheme 2

KINETICS AND MECHANISM OF OXIDATION OF D-FRUCTOSE AND D-GLUCOSE
581
Scheme 2 Continued
reasonably linear with isokinetic temperatures of 301 K
and 299 K for fructose and glucose oxidations, respec-
tively. Further, to see the effect of substitution in the
oxidants on the energy of activation, Ea values of N-
chloroarylsulfonamides were optimized with reference
to log A of the parent oxidant, N-chlorobenzenesul-
fonamide through the equation, Ea = 2.303 RT (log A
ilarly, log A values for the oxidations of both fructose
and glucose by the substituted oxidants were optimized
with reference to Ea of the parent oxidant through the
equation, log A = log kobs + Ea/2.303 RT (Tables V
and VI). Log A values are slightly higher for the oxi-
dants with electron-withdrawing groups in the benzene
ring, while the effect of electron-releasing groups on
log A is negligible. The free energies of activation re-
main almost the same indicating operation of similar
mechanisms in all the cases.
–
log kobs). The energies of activation for the oxida-
tion of either D-fructose or D-glucose by the oxidants
with electron-releasing groups in the benzene ring are
slightly higher than that of the parent oxidant, while
the values are little lower for the oxidants with electron
withdrawing groups in the benzene ring (Tables V and
VI). Enthalpies of activations have the same trend. Sim-
Effective oxidizing species of the oxidants em-
+
ployed in the present oxidations is Cl in differ-
ent forms, released from the oxidant. The introduc-
tion of different substituents into the benzene ring

582
GOWDA, DAMODARA, AND JYOTHI
of the oxidant affects the ability of it to release
Cl and hence its capacity to oxidize the substrate.
8. Gowda, B. T.; Ramachandra, P. J Chem Soc, Perkin
Trans 1989, 2, 1067.
+
9. Agrawal, M. C.; Upadhyay, S. K. J Sci Ind Res 1990,
It is evident from the rate data that the electron-
releasing groups such as CH3, C2H5 etc. inhibit the
49, 13.
+
10. Gowda, B. T.; D’Souza, J. D.; Bhat, K. R. J Indian Chem
Soc 2002, 78, 412.
ease with which Cl is released from the oxidant,
while electron-withdrawing groups such as Cl, Br
etc. enhance this ability and hence influence the rates
of oxidations. The kinetic data for the oxidations of
D-fructoseandD-glucoseby N-chloroarylsulfonamides
have been intercorrelated in terms of the observed rate
constants and thermodynamic parameters (figures not
shown). These correlations were reasonably good.
A typical detailed mechanism of oxidation of fruc-
tose isomer by an oxidant is schematically shown in
Scheme 2.
1
1
1
1. Gowda, B. T.; Kumar, B. H. A. Oxid Commun 2003, 26,
03.
2. Gowda, B. T.; Jyothi, K.; D’Souza, J. D. Z Naturforsch,
A: Phys Sci 2002, 57, 967.
3. Gowda, B. T.; D’Souza, J. D.; Kumar, B. H. A. Z
Naturforsch, A: Phys Sci 2003, 58, 51.
4
14. Shetty, M.; Gowda, B. T. Z Naturforsch, B: Chem Sci
2004, 58, 63.
1
1
1
5. Gowda, B. T.; Shetty, M. J Phys Org Chem 2004, 17,
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6. Morrison, R. T.; Boyd, R. N. Organic Chemistry;
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7. (a) Schaffer, R. In The Carbohydrates; Pigman, W.;
Horton, D. (Eds.); Academic: New York, 1980; Vol. 1A.
BIBLIOGRAPHY
(b) Green, J. W. In The Carbohydrates; Pigman, W.;
1
2
3
4
. Campbell, M. M.; Johnson, G. Chem Rev 1978, 78,
5.
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Horton, D. (Eds.); Academic: New York, 1980: Vol. 1B.
18. Mahadevappa, D. S.; Puttaswamy, T. A. I. Carbohydr
Res 1990, 204, 197.
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19. Rangappa, K. S.; Manjunathaswamy, H.; Raghavendra,
M. P.; Gowda, D. C. Carbohydr Res 1998, 307, 253.
20. Stahl, E. Thin Layer Chromatography, A Laboratory
Hand Book; Springer: New York, 1969.
21. Pigman, W.; Anet, E. F. L. J. In The Carbohydrates:
Chemistry and Biochemistry, 2nd ed.; Pigman, W.;
Horton, D. (Eds.); Academic: New York, 1972; Vol. 1A,
p. 165.
. Gowda, B. T.; Sherigara, B. S.; Mahadevappa, D. S.
Microchem J 1986, 34, 103.
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22. Hammett, L. P. Physical Organic Chemistry, 2nd ed.;
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2