Kinetic and mechanistic study of oxidation of diethylamine by N-sodio-N-bromobenzene sulphonamide (Bromamine-B) in acid solution: Catalyzed by Ru(III)

Article abstract of DOI:10.1002/(SICI)1097-4601(1999)31:10<744::AID-JCK8>3.0.CO;2-N

Kinetics of oxidation of diethylamine (DEA) by Bromamine-B (BAB) has been investigated at 303 K in acid solution with Ru(III) as catalyst. The oxidation behavior obeys the rate law, rate = k [BAB] [DEA] [Ru(III)] [H⁺]^-x where `x' is less than unity indicating retardation of rate by [H⁺]. Added halide ions, the reaction product benzenesulphonamide, variation of ionic strength and dielectric constant of the medium do not have any significant effect on the rate. The protonation constant of monobromamine-B evaluated for the reaction is 32.3 at 303 K. Activation parameters have been evaluated from Arrhenius plot. A mechanism consistent with experimental results has been proposed.

Full text of DOI:10.1002/(SICI)1097-4601(1999)31:10<744::AID-JCK8>3.0.CO;2-N

Kinetic and Mechanistic
Study of Oxidation of
Diethylamine by N-Sodio-N-
Bromobenzene
Sulphonamide
(Bromamine-B) in Acid
Solution: Catalyzed by
Ru(III)
S. ANANDA, RAVI J. D. SALDANHA, K. M. L. RAI, B. M. VENKATESHA
Department of Studies in Chemistry, University of Mysore, Manasagangothri, Mysore 570 006, India
Received 3 August 1998; accepted 22 June 1999
ABSTRACT: Kinetics of oxidation of diethylamine (DEA) by Bromamine-B (BAB) has been
investigated at 303 K in acid solution with Ru(III) as catalyst. The oxidation behavior obeys
x
the rate law, rate ϭ k [BAB] [DEA] [Ru(III)] [Hϩ]Ϫ where ‘x’ is less than unity indicating
retardation of rate by [Hϩ]. Added halide ions, the reaction product benzenesulphonamide,
variation of ionic strength and dielectric constant of the medium do not have any significant
effect on the rate. The protonation constant of monobromamine-B evaluated for the reaction
is 32.3 at 303 K. Activation parameters have been evaluated from Arrhenius plot. A mechanism
consistent with experimental results has been proposed. ᭧ 1999 John Wiley & Sons, Inc. Int J Chem
Kinet 31: 744–752, 1999
INTRODUCTION
by periodate by Hiremath et al. [1]. Recently, Jabhas
et al. [2] have reported oxidation of Aliphatic amines
including DEA by N-bromopthalamide (NBP). How-
ever, a very few kinetic investigations of diethylamine
oxidations have been reported. There is no information
available on the oxidation by haloamines. The present
studies were undertaken to investigate the kinetic as-
pects of oxidation of diethylamine by N-metallo-N-
haloarysulphonamides. Mechanistic studies of the ox-
idation of diverse organic substrates by these organic
Diethylamine (DEA) is an intermediate for rubber ac-
celerators, pharmaceuticals, dyestuff, textile finishing
agents and corrosion inhibitors. It is commonly used
as an intermediate in the synthesis of procaine anes-
thetic and antihistamine. Diethylamine was oxidized
Correspondence to: S. Ananda
᭧ 1999 John Wiley & Sons, Inc.
CCC 0538-8066/99/100744-09

OXIDATION OF DIETHYLAMINE BY N-SODIO-N-BROMOBENZENE SULPHONAMIDE
745
haloamines have been reported previously [3–5]. We
C2H5NHC2H5 ϩ 2PhSO2NBrNa ϩ 2H2O
!: 2CH3CHO ϩ 2PhSO2NH2
now report a detailed investigation of the kinetics of
oxidation of diethylamine (DEA) by Bromamine-B in
acid solution catalyzed by Ru(III) at 303 K.
ϩ NH3 ϩ 2Naϩ ϩ 2Br (1)
The presence of aldehyde which is the oxidation
product of DEA in the reaction mixture was detected
by preparing its 2,4-dinitrophenylhydrazone deriva-
tive and by using Tollens reagent and chromic acid
tests [8]. The other product, ammonia, was quantita-
tively estimated by the standard microkjeldhal proce-
dure. In a typical experiment, 5 ϫ 10Ϫ5 moles of BAB
EXPERIMENTAL
The oxidant, BAB, was prepared and purified using
the standard methods [6,7]. Its purity was checked io-
dometrically and through IR and NMR spectral data.
Aqueous solution of BAB was prepared, standardized
by the iodometric method and preserved in amber col-
ored bottles. Analar grade diethylamine (E. Merck)
was used and aqueous solution of the substrate was
prepared. Solution of RuCl3 (Arora Matthey) in
3
were mixed with 2 ϫ 10Ϫ moles of diethylamine in
a total volume of 20 ml under experimental conditions.
The NH3 formed was distilled and absorbed in 2%
boric acid solution. It was then titrated against 0.01 M
HCl using a mixed indicator (methyl red—bromocre-
sol green). The solution consumed 2.5CC of 0.01M
3
0.5 mol dmϪ HCl was used as catalyst in acid solu-
5
HCl corresponding to the formation of 2.5 ϫ 10Ϫ
tion. Allowance was made for the amount of HCl
present in the catalyst solution while preparing solu-
tions for kinetic runs. All other chemicals used were
of accepted grades of purity. Triply distilled water was
used for preparing aqueous solutions. Ionic strength of
reaction mixture was kept at a high value with a con-
centrated solution of NaClO4 (E. Merck).
moles of NH3 . The reaction product benzenesulphon-
amide was detected by paper chromatography, using
benzyl alcohol saturated with water as the solvent sys-
tem with ascending irrigation and using 0.5% vanillin
in 1% HCl, in ethanol as the spray reagent (Rf ϭ
0.905).
RESULTS
Kinetic Measurements
The reaction performed in the presence of Ru(III)
and HCl, under pseudo-first-order conditions of
[DEA] ϾϾ [BAB], gave a linear plot of log [BAB]
versus time (r Ͼ 0.9981). The linearity of these plots
together with the constancy of the slope at various
[BAB]o indicate a first-order dependence of the reac-
tion rate on [BAB]. The pseudo-first-order rate con-
stants, kЈ, obtained at 303 K are listed in Table I. The
reaction rate increased with increase in [DEA]o and
plot of log kЈ versus log [DEA]o was linear (r ϭ 0.998)
with unit slope showing a first-order dependence of
the rate on [DEA]o (Table I, Fig. 1). At fixed [BAB]o
and [DEA]o , the rate of reaction decreased with in-
crease in [HCl] (Table II). The plot of log kЈ versus
log [HCl] was linear (r ϭ 0.998) with slope equal to
Ϫ0.5, indicating inverse fractional order in [HCl]. Ad-
dition of ClϪ or Br Ϫ ions in the form of NaCl or
NaBr at known [Hϩ] and ionic strength did not affect
the rate. Hence, the dependence of the rate on [HCl]
reflected the effect of [Hϩ] only on the reaction. The
rate increased with an increase in [Ru(III)] and plot of
log kЈ versus log[Ru(III)] was linear with unit slope
showing a first-order dependence on [Ru(III)] (Table
III, Fig. 2). Addition of reaction product benzenesul-
phonamide (2.0 ϫ 10Ϫ4 Ϫ 8.0 ϫ 10Ϫ4 mol dmϪ3) and
the variation of ionic strength of the medium by adding
The kinetic runs were carried out in stoppered pyrex
glass tubes whose outer surfaces were coated black to
eliminate photochemical effects. Requisite amount of
the amine substrate, NaClO4 , RuCl3 , and HCl solu-
tions and water (to maintain a constant total volume
for all runs) were taken in the tubes and thermally
equilibrated in a water bath, set at a given temperature
(30 Ϯ 0.1ЊC). To this solution was added a mea-
sured amount of preequilibrated standard BAB
solution of known concentration. The progress of
the reaction was monitored iodometrically for two
half-lives by withdrawing aliquots of the reaction mix-
ture at regular time intervals. The pseudo-first-order
rate constants kЈ calculated were reproducible within
Ϯ3%.
Stoichiometry and Product Analysis
Reaction mixtures containing different compositions
of BAB and DEA were equilibrated at 30ЊC in
2
3
presence of 6.0 ϫ 10Ϫ mol dmϪ HCl and 19.28 ϫ
10Ϫ mol dmϪ Ru(III) for 24 hours. The iodometric
determination of unreacted BAB in the reaction mix-
ture showed that two moles of BAB were consumed
per mole of the DEA according to Eq. (1).
5
3

746
ANANDA ET AL.
Table I Effect of Varying Reactant Concentrations on
Table II Effect of Varying Hydrogen Ion Concentra-
the Rate
tion on the Reaction Rate
5
2
[Hϩ] ϭ 6.0 ϫ 10Ϫ2 mol dmϪ3, [Ru(III)] ϭ 19.28 ϫ 10Ϫ
[BAB]o ϭ 6.0 ϫ 10Ϫ4 mol dmϪ3, [DEA] ϭ 3.5 ϫ 10Ϫ
mol dmϪ3, ␮ ϭ 0.3 mol dmϪ3, Temp ϭ 303 K
mol dmϪ3, [Ru(III)] ϭ 19.28 ϫ 10Ϫ5 mol dmϪ3, ␮ ϭ 0.3
mol dmϪ3, Temp ϭ 303 K
[BAB] ϫ 104
mol dm
[DEA] ϫ 102
Ϫ
3
Ϫ
3
Ϫ
1
ϩ
Ϫ
3
Ϫ1
mol dm
kЈ ϫ 104 (s
)
[H ] ϫ 102 mol dm
kЈ ϫ 104 (s
)
3.0
4.0
5.0
6.0
7.0
8.0
6.0
6.0
6.0
6.0
6.0
6.0
6.0
6.0
3.5
3.5
3.5
3.5
3.5
3.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
4.39 (1.01)
4.37 (0.96)
4.31 (0.99)
4.35 (1.02)
4.30 (0.97)
4.32 (0.98)
2.47 (0.57)
3.12 (0.69)
3.71 (0.86)
4.35 (0.98)
4.95 (1.14)
5.56 (1.28)
6.18 (1.38)
6.88 (1.53)
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
6.85 (1.51)
5.73 (1.24)
4.96 (1.07)
4.35 (0.98)
3.93 (0.88)
3.60 (0.83)
3.35 (0.74)
3.15 (0.71)
The values in the parenthesis are for the uncatalyzed oxidation
of DEA by BAB in presence of HCl.
NaCIO4 (0.01–0.3 mol dmϪ3) had no effect on the
reaction rate. The variation of the solvent composition
using MeOH (0–15%) did not affect the rate effec-
tively.
The values in parenthesis are for the uncatalyzed oxidation of
DEA by BAB in HCl medium.
The reaction was studied at varying temperatures
298 K to 313 K. The activation parameters, namely
Ϫ
Ϫ
ϩ
Ϫ
Ϫ
Figure 1 Plot of logkЈ versus log [DEA] [BAB]O ϭ 6.0 ϫ 10 4 mol dm 3; [H ] ϭ 6.0 ϫ 10 2 mol dm 3; [Ru(III)] ϭ 19.28
Ϫ
Ϫ
Ϫ
ϫ 10 5 mol dm 3; ␮ ϭ 0.3 mol dm 3 Temp ϭ 303 K.

OXIDATION OF DIETHYLAMINE BY N-SODIO-N-BROMOBENZENE SULPHONAMIDE
747
Table III Effect of Varying [Ru(III)] Catalyst Concentration on the Reaction Rate
[BAB]o ϭ 6.0 ϫ 10Ϫ4 mol dmϪ3, [DEA] ϭ 3.5 ϫ 10Ϫ2 mol dmϪ
[Hϩ] ϭ 6.0 ϫ 10Ϫ2 mol dmϪ3, ␮ ϭ 0.3 mol dmϪ3, Temp ϭ 303 K
3
,
[Ru(III)] ϫ 105
k1 Ϫ ko
Kc ϭ
Ϫ
3
Ϫ
1
Ϫ1
kЈ ϫ 104 (s
)
ko ϫ 104 (s
)
[Ru(III)]
mol dm
4.82
9.64
1.04
2.14
3.24
4.35
5.42
6.54
8.74
q
s
s
—
1.203
14.46
19.28
24.10
28.92
38.56
1.562
1.747
1.842
1.922
2.012
0.98
s
s
p
energy of activation (Ea), enthalpy of activation
study, however, the chloride ion has no effect on the
Þ
Þ
Ϫ
(⌬H ), entropy of activation (⌬S ) and free energy of
rate which indicates that the complex ion [RuCl6]3
,
Þ
activation (⌬G ) were obtained from the Arrhenius
is the reactive catalyst species that interacts with the
amine to form a complex intermediate. Similar results
were observed in the Ru(III) catalyzed oxidation of
chloroacetic acids by bromamine-T (BAT) [16] and
bromamine-B [17] and aliphatic primary amines by
BAT [18].
Pryde and Soper [19], Morries et al. [20], and
Bishop and Jennings [21] have shown the existence of
similar equilibrium in acid and alkaline solutions of
N-metallo-N-haloary1-sulphonamides. Bromamine-B
(PhSO2NBrNa), like chlorine analogue chloramine-T,
behaves as a strong electrolyte in aqueous solutions
forming different species as shown in Eqs. (3–7).
plot of log kЈ versus 1/T, which was linear. The kinetic
and activation parameters data obtained were pre-
sented in Table IV.
The reaction was also studied in the absence
of Ru(III). Under pseudo-first-order conditions of
[DEA] ϾϾ [BAB], a linear plot of log [BAB] time was
obtained. The linearity of this plot, together with the
constancy of the slope at various [BAB]o , indicates a
first-order dependence of the reaction rate on [BAB].
Similar results were observed for the variation of
[DEA] and [HCl] as in the case of oxidation of
DEA by BAB in presence of Ru(III) catalyst. The rate
constants kЈ obtained at 303 K are listed in Tables I
and II.
PhSO2NBrNa EF PhSO2NBrϪ ϩ Naϩ
PhSO2NBrϪ ϩ Hϩ EF PhSO2NHBr
(3)
(4)
DISCUSSION AND MECHANISM
PhSO2NHBr ϩ H2O EF PhSO2NH2 ϩ HOBr (5)
2PhSO2NHBr EF PhSO2NH2 ϩ PhSO2NBr2 (6)
Cady and Connick [9] and Connick and Fine [10] have
determined the formula of aqueous ruthenium (III)
complex species using the ion exchange resin prop-
erties and UV spectral studies. These studies have
HOBr ϩ Hϩ EF H2OBrϩ
(7)
shown that the octahedral complex species such as
2
[RuCl5(H2O)]Ϫ
,
[RuCl4(H2O)2]Ϫ, [RuCl3(H2O)3],
[RuCl2(H2O)4]ϩ, and [RuCl(H2O)5]ϩ do not exist in
aqueous solutions of RuCl3 . Other studies have shown
that the following equilibrium exists for Ru(III) in
acidic solution [11–13].
2
In acidic solution, the probable oxidizing species
are the free acid (PhSO2NHBr), dibromamine-B
(PhSO2NBr2), HOBr, and H2OBrϩ.
The involvement of PhSO2NBr2 in the mechanism
leads to a second-order rate law according to Eq. (8),
which is contrary to the experimental observations. As
Eq. (5) indicates a slow hydrolysis, if HOBr were the
primary oxidizing species, a first-order retardation of
the rate by the added PhSO2NH2 would be expected,
contrary to the experimental results. Hardy and John-
ston [22], who have studied the pH-dependence of rel-
Ϫ
Ϫ
[RuCl6]3 ϩ H2O EF [RuCl5(H2O)]2 ϩ ClϪ (2)
Singh et al. [14, 15] used the above equilibrium in
the ruthenium (III) chloride catalyzed oxidation of pri-
mary alcohols by BAB and of ethylene glycols by N-
bromoacetamide in HClO4 medium. In the present

748
ANANDA ET AL.
Ϫ
4
Ϫ
Ϫ
2
Ϫ
ϩ
Figure 2 Plot of logkЈ versus log[Ru(III)]. [BAB]O ϭ 6.0 ϫ 10 mol dm 3; [DEA] ϭ 3.5 ϫ 10 mol dm 3; [H ] ϭ 6.0
Ϫ
Ϫ
Ϫ
ϫ 10 2 mol dm 3; ␮ ϭ 0.3 mol dm 3; Temp ϭ 303 K.
ative concentrations of the species present in acidified
chloramine-T solution of comparable molarities, have
shown that PhSO2NHBr is the likely oxidizing species
in acid medium. Narayanan and Rao [23] and Sub-
hashini et al. [24] have reported that monohaloamines
can be further protonated at pH ϽϽ 2 as shown in the
following Eqs. (8) and (9) for chloramine-T (p-Me-
C6H4SO2NHCl) and chloramine-B (C6H4SO2NHCl),
respectively.
p-CH3C6H4SO2NHCl ϩ Hϩ
EF [p-CH3C6H4SO2NH2Cl]ϩ (8)
C6H5SO2NHCl ϩ Hϩ EF [C6H5SO2NH2Cl]ϩ (9)
Table IV Temperature Dependence of the Reaction
Rate and Activation Parameters of the Oxidation of
Diethylamine by Bromamine-B
The second protonation constant for chloramine-T
(p-CH3-C6H4SO2NHCl) and chloramine-B (C6H5-
2
[BAB]o ϭ 6.0 ϫ 104 mol dmϪ3, [DEA] ϭ 3.5 ϫ 10Ϫ
1
SO2NHCl) are 102 MϪ1 and 61 Ϯ 5 MϪ , respectively,
3
mol dmϪ
at 298 K [23,24] Gupta [25] believes that the values
could be lower than those reported by the above work-
ers. In the present case, the inverse fractional order
5
[Hϩ] ϭ 6.0 ϫ 10Ϫ2 mol dmϪ3, [Ru(III)] ϭ 19.28 ϫ 10Ϫ
3
mol dmϪ
␮ ϭ 0.3 mol dmϪ3, Temp ϭ 303 K
in [Hϩ] suggests that the deprotonation of
ϩ
Temperature
PhSO2NH2Br results in the formation of PhSO2NHBr,
species which is likely to be the active oxidant in-
volved in the mechanism of amine oxidation. And the
zero effect of the ionic strength indicates that the slow
step involves at least one neutral species.
Ϫ
1
(K)
k ϫ 104 (S
)
Activation Parameters
Ϫ
1
298
303
308
313
2.71
4.35
6.62
Ea ϭ 56.8 kJ mol
Þ
Ϫ1
⌬H ϭ 54.2 kJ mol
Þ
Ϫ1
Ϫ1
⌬S ϭ Ϫ130 JK mol
Þ
Ϫ1
10.23
⌬G ϭ 94.0 kJ mol
Furthermore, ultraviolet spectral measurements

OXIDATION OF DIETHYLAMINE BY N-SODIO-N-BROMOBENZENE SULPHONAMIDE
749
showed that diethylamine solution has a sharp absorp-
Ϫd[BAB]t
rate ϭ
tion band at 369 nm while a band around 217 nm was
noticed for Ru(III), and 227 nm for BAB solution in
presence of 0.06 mol dmϪ3 HCl. A mixture of diethy-
lamine and Ru(III) solution in presence of 0.06 mol
dmϪ3 HCl showed an absorption band at 318 nm while
for the mixture of BAB and Ru(III) solutions there was
no change in the ␭max at 227 nm, indicating that com-
plex formation takes place only between Ru(III) and
substrate. Based on the preceding discussion, a mech-
anism (Scheme I) is proposed for the reaction.
dt
K1K2k3[BAB]t [S] [Ru(III)]
[Hϩ] ϩ K1
ϭ
(14)
Which is in good agreement with the experimental
results. A detailed mechanism of Ru(III) catalyzed ox-
idation of DEA by BAB in HCl medium is given in
Scheme II. An initial equilibrium involves deproton-
ϩ
ation of PhSO2NH2Br forming the active oxidizing
species of BAB, PhSO2NHBr (step (i) in Scheme I,
but not shown in Scheme II). In the next fast pre-
equilibrium, the nitrogen atom of the amine coordi-
nates to the metal center of the active catalyst species,
[RuCl6]3Ϫ to form a loosely bound metal complex an-
ion X (step 1 of Scheme II) trapped in a solvent cage.
This is similar to an associative interchange mecha-
nism involving a fast pre-equilibrium in ligand sub-
stitution reactions of metal complexes. This kind of
loose metal ion substrate complex formation has been
used as an intermediate in some studies involving
Ru(III) catalyst [11]. Then an electrophilic attack by
PhSO2NHBr at the amino nitrogen of X displaces
ϩ
K1
PhSO2NH2Br E
R
F PhSO2NHBr ϩ Hϩ (i) fast
K2
S ϩ Ru(III) E
R
F X
(ii) fast
complex
k3
PhSO2NHBr ϩ X 9
9
: XЈ
complex
ϩ Ru(III) (iii) slow
XЈ !: XЉ
complex
ϩ PhSO2NH2 (iv) fast
[RuCl6]3 to form the next intermediate species X1
Ϫ
[step (ii) of Scheme II]. In step (iii) the intermediate
XЈ undergoes fast intramolecular rearrangements
forming an intermediate XЉ and PhSO2NH2 . In step
(iv), a nucleophilic attack by H2O on the ␣-C␦ϩ atom
of the C9N bond of the neutral species XЉ and intra-
molecular rearrangements results in the formation of
an ␣-hydroxy amine intermediate Xٞ. This interme-
diate undergoes disproportionation to give acetalde-
hyde and ethylamine. Ethylamine further undergoes a
similar type of oxidation consuming one equivalent of
BAB resulting in the formation of CH3CHO and NH3 .
Overall, one molecule of diethylamine consumes two
molecules of BAB for complete oxidation, liberating
two molecules of CH3CHO and one molecule of NH3 .
Since rate ϭ kobs [BAB], Eq. (14) can be trans-
formed into Eqs. (15) and (16).
XЉ ϩ H2O !: Products
Scheme I
(v) fast
From the slow step of the preceding Scheme I
Ϫd[BAB]t
rate ϭ
ϭ k3[PhSO2NHBr] [X] (10)
dt
The total effective concentration of BAB, from
Scheme I is given by Eq. (11).
ϩ
[BAB]t ϭ [PhSO2NH2Br] ϩ [PhSO2NHBr] (11)
By substituting for [PhSO2NH2Br] from equilib-
rium (i) into Eq. (11) and solving for [PhSO2NHBr],
one gets
1
[Hϩ] ϩ K1
ϭ
(15)
kobs K1K2k3 [S] [Ru(III)]
K1[BAB]t
[Hϩ] ϩ K1
[PhSO2NHBr] ϭ
(12)
1
[Hϩ]
ϭ
kobs K1K2k3 [S] [Ru(III)]
From Scheme 1 step (ii)
[X] ϭ K2[S] [Ru(III)]
1
ϩ
(16)
K2k3 [S] [Ru(III)]
(13)
From the plot of 1/kobs versus [Hϩ] (Fig. 3) the value
of K2k3 ϭ 193.2 and K1 ϭ 3.1 ϫ 10Ϫ mol dmϪ or
protonation constant (1/K1 ϭ Kp) is 32.3 for the spe-
2
3
Substituting [PhSO2NHBr] and [X] in Eq. (10) we
get the rate law Eq. (14).

750
ANANDA ET AL.
H
H
H
Fast
I. C2H59N ϩ (RuCl6)3Ϫ
V. H3C9C9N ϩ Br HNSO2Ph
H
H
C2H5
H
ϩ
H
H
3Ϫ
␦
ϩ
Ϫ
C2H59N (␦RuCl6)
Ϫ
H3C9C9N ϩ PhSO2NH
H
C2H5
H
Br
(X)
H
H
ϩ
Ϫ
H C9C9N
ϩ PhSO2NH
VI.
3
H
H
␦
ϩ
H
Br
II. C2H59N (␦RuCl6)3Ϫ ϩ Br HN SO2Ph
Ϫ
H
H
C2H5
ϩ
CH39C"N ϩ PhSO2NH2 ϩ BrϪ
H
Ϫ
H
Slow
CH39C9N9Br ϩ PhSO2NH
Ϫ(RuCl6)3Ϫ
H
O9H
CH39C"N
H
H
H
H
H
H
CH2
CH3
ϩ
ϪHϩ
VII. H3C9C"N
O
( )
XI
H
H
CH3CHO ϩ NH3
H
Scheme II
Ϫ
III. CH39C9N9Br ϩ PhSO2NH
H
CH2
CH3
cies PhSO2NHBr were evaluated from the intercept
and slope, respectively. The protonation constant
value obtained is in good agreement with the previ-
ously published work [18] which gives an indirect ev-
idence for the proposed mechanism of the Scheme I.
It has been pointed out by Moelwyn and Hughes
[26] that in the presence of the catalyst, the uncataly-
zed and catalyzed reactions proceed simultaneously so
that
H
CH39C"N9C9CH3
H
H
ϩ PhSO2NH2 ϩ Br Ϫ
(
XII
)
k1 ϭ ko ϩ Kc[catalyst]x
H
H
Successive addition of the catalyst brings about
proportionate increase in the observed velocity, ‘x’ is
unity and Kc becomes a bimolecular constant. In the
present study it has been found that the value of the
rate constant is directly proportional to the concentra-
tion of the catalyst Ru(III) ion and therefore ‘x’ is
unity and the relation will be
IV. CH39C"N9C9CH3
O
H
H
H
O9H
CH39C9N9CH2CH3
k1 ϭ ko ϩ Kc [Ru(III)]
H
H
CH3CHO ϩ CH3CH2NH2
Where k1 is observed pseudo-first-order rate con-
stant in the presence of the catalyst Ru(III), ko is the
(
XIII
)

OXIDATION OF DIETHYLAMINE BY N-SODIO-N-BROMOBENZENE SULPHONAMIDE
751
ϩ
Ϫ
Ϫ
Ϫ
2
Ϫ
Figure 3 Plot of 1/kЈ versus [H ] [BAB]O ϭ 6.0 ϫ 10 4 mol dm 3; [DEA] ϭ 3.5 ϫ 10 mol dm 3; [Ru(III)] ϭ 19.28 ϫ
Ϫ5
Ϫ
Ϫ
10 mol dm 3; ␮ ϭ 0.3 mol dm 3; Temp ϭ 303 K.
pseudo-first-order rate constant for the uncatalyzed re-
action and Kc is the catalytic constant. The values of
Kc obtained from
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InkЈ ϭ Inkϱ ϩ 3/8kT (2/D-1) ␮ 2/rA
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(17)
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should be higher in a medium of lower dielectric con-
3
3
3
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of charge dispersal in the transition state is different.
3
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