Effect of solvent on the kinetics of arylsulfonylation of N-alkylated anilines in a water-propan-2-ol system

Article abstract of DOI:10.1007/s11172-006-0364-2

The effect of the composition of a water-propan-2-ol solvent on the kinetics of arylsulfonylation of N-ethyl-, N-isopropyl-, and N-butylanilines with 3-nitrobenzenesulfonyl chloride at 298 K was studied. The reaction rate constant increases monotonically with an increase in the water fraction in the solvent from 5 to 30 wt.%. The apparent activation parameters of the reaction of N-butylaniline with 3-nitrobenzenesulfonyl chloride were calculated. No considerable changes in the activation parameters of the reaction were observed on going from pure propan-2-ol to a 10% aqueous solution, which indicates that the mechanism remains unchanged upon solvent change. Propan-2-ol with a water content of 5-30 wt.% can be used in the synthesis of arylsulfonylation products of the amines under study in 98-99% yield.

Full text of DOI:10.1007/s11172-006-0364-2

Russian Chemical Bulletin, International Edition, Vol. 55, No. 6, pp. 973—975, June, 2006
973
Effect of solvent on the kinetics of arylsulfonylation of
Nꢀalkylated anilines in a water—propanꢀ2ꢀol system
T. P. Kustovaꢀ and I. O. Sterlikova
Ivanovo State University,
39 ul. Ermaka, 153025 Ivanovo, Russian Federation.
Fax: +7 (493 2) 32 6600. Eꢀmail: kustova_t@mail.ru
The effect of the composition of a water—propanꢀ2ꢀol solvent on the kinetics of
arylsulfonylation of Nꢀethylꢀ, Nꢀisopropylꢀ, and Nꢀbutylanilines with 3ꢀnitrobenzenesulfonyl
chloride at 298 K was studied. The reaction rate constant increases monotonically with an
increase in the water fraction in the solvent from 5 to 30 wt.%. The apparent activation
parameters of the reaction of Nꢀbutylaniline with 3ꢀnitrobenzenesulfonyl chloride were calcuꢀ
lated. No considerable changes in the activation parameters of the reaction were observed on
going from pure propanꢀ2ꢀol to a 10% aqueous solution, which indicates that the mechanism
remains unchanged upon solvent change. Propanꢀ2ꢀol with a water content of 5—30 wt.% can
be used in the synthesis of arylsulfonylation products of the amines under study in 98—99%
yield.
Key words: arylsulfonylation, Nꢀalkylated anilines, kinetics, 3ꢀnitrobenzenesulfonyl chloꢀ
ride, water—propanꢀ2ꢀol system.
We have previously1,2 studied the kinetics of arylꢀ
sulfonylation of Nꢀalkylated anilines and Nꢀisobutylꢀ
anilines substituted at the benzene ring with 3ꢀnitroꢀ
benzenesulfonyl chloride in several organic solvents
at 298 K. It was found that the rate constants of all the
reactions under study lie in an interval of (0.16—29.24)•
•10–2 L mol–1 s–1. Therefore, it seems of interest to search
for mixed solvents accelerating the reactions of Nꢀalkylꢀ
arylamines with aromatic sulfonyl chlorides. Our previous
studies3 of the similar reaction of aromatic amines with
3ꢀ and 4ꢀnitrobenzenesulfonyl chlorides showed that the
arylsulfonylation rate constant increases substantially
when waterꢀorganic solvents (water—propanꢀ2ꢀol, waꢀ
ter—dioxane, water—acetonitrile) are used. Interest in
water as a component of solvents is caused by its amphiꢀ
protic nature and profitable use in practice of organic
synthesis.
In the present work, we studied the kinetics of the
reaction of Nꢀsubstituted anilines with 3ꢀnitrobenzeneꢀ
sulfonyl chloride (Scheme 1) and calculated the activaꢀ
tion parameters of the reaction and the yields of the target
product at different initial concentrations of the reactants
and solvent compositions.
Experimental
Scheme 1
The kinetics of the reaction of amines 1a—c with sulfonyl
chloride 2 was studied by conductometry using an E7ꢀ14 elecꢀ
tric conduction meter equipped with an OKꢀ9023 circular platiꢀ
num electrode. The initial concentration of alkylarylamine in
the working solution was twice as large as the initial concentraꢀ
tion of the arylsulfonylating agent, being 1•10–2 mol L–1
.
In a water—propanꢀ2ꢀol solvent, the reaction of amines 1a—c
with sulfonyl chloride 2 is accompanied by the hydrolysis and
alcoholysis of the latter (Scheme 2).
It has previously4 been shown that for aniline acylation with
benzenesulfonyl chloride the conversion of the sulfonyl chloride
due to solvolysis in methanol does not exceed 2—3%, whereas in
other alcohols (ethanol, propanol, etc.) alcoholysis occurs more
slowly. Therefore, when calculating the arylsulfonylation rate
constant, we neglected the alcoholysis of sulfonyl chloride 2.
The rate constant of hydrolysis of sulfonyl chloride 2 (kh) was
1: R = Et (а), Pri (b), Bu (с)
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 937—939, June, 2006.
1066ꢀ5285/06/5506ꢀ0973 © 2006 Springer Science+Business Media, Inc.

974
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 6, June, 2006
Kustova and Sterlikova
Scheme 2
Table 1. Rate constants of acylation of amines 1a,c with sulfonyl
chloride 2 (kac) and hydrolysis of sulfonyl chloride 2 (kh) in a
water—propanꢀ2ꢀol solvent at different water contents in the
mixtures (298 K)
ω
XH O
*
kac•102/L mol–1 s–1
kh•104
/s–1
H O
2
2
(wt.%)
1а
1с
0
5
0.00
0.15
0.27
0.37
0.45
0.52
0.59
5.00 0.01
—
10.60 0.30
—
16.00 0.10
—
21.50 0.60
3.21 0.02
5.21 0.04
7.44 0.09
9.45 0.04
11.20 0.08
13.10 0.25
15.20 0.25
—
1.26 0.04
1.63 0.02
1.69 0.01
2.09 0.03
2.19 0.02
2.35 0.01
10
15
20
25
30
determined during a special kinetic experiment and then taken
into account in the calculation of the reaction rate constant (kac)
(see Scheme 1).
* Mole fraction (here and in Table 2).
The kinetics of the reaction of amines 1a—c with sulfonyl
chloride 2 is described by a kinetic equation of the second order
impossible to calculate the reaction rate constants (see
Scheme 1). The steric factor exerts, most likely, the deciꢀ
sive effect on the kinetics of arylsulfonylation of Nꢀisoꢀ
propylaniline and, therefore, a substantial increase in kac
cannot be attained even by a change in the solvent nature.
Then we studied the reaction of amines 1a,c with the
Nꢀalkyl substituent of normal structure. The kac and kh
values for the reaction of these amines with sulfonyl chloꢀ
ride 2 in a water—propanꢀ2ꢀol solvent at different water
contents in the mixture are presented in Table 1.
–dcsc/dτ = kaccamcsc + khcsc,
(1)
where cam and csc are the current concentrations of amine and
acid chloride, respectively; τ is time.
The arylsulfonylation rate constant with allowance for hyꢀ
0
0
drolysis of sulfonyl chloride 2 at сam = 2сsc was calculated by
the equation
,
(2)
It is seen that kac increases monotonically with an
increase in the water content in the binary solvent, and
0
where (сsc0 – x) = csc •(æ∞ – æτ)/(æ∞ – æ0); æ0, æτ, and æ∞ are
the conductions of the reaction mixture at the initial moment τ ,
0
at the time moment τ, and after the end of the reaction, respecꢀ
tively; csc is the initial concentration of sulfonyl chloride; x is
0
Table 2. Results of calculation of the yield of the arylsulfonylation
product (α ) and the content of 3ꢀnitrobenzenesulfonic acid
the change in the sulfonyl chloride concentration to the
moment τ.
ac
admixture (α ) in the water—propanꢀ2ꢀol solvent at different
h
water contents in the mixtures (298 K)
Amines (Aldrich) with the main substance content 98—99%
were used without additional purification. Compound 2 (pure
grade) was recrystallized from heptane. Propanꢀ2ꢀol (reagent
grade) was distilled on a column under atmospheric pressure.
All solutions containing water were prepared using bidistilled
water.
0
ω
XH O
csc
α
(%)
α (%)
H O
ac
h
2
2
(wt.%)
/mol L–1
1а
1с
1а + 2 1с + 2
5
0.15
0.15
0.15
0.27
0.27
0.27
0.37
0.37
0.37
0.45
0.45
0.45
0.52
0.52
0.52
0.59
0.59
0.59
0.005
0.1
0.5
0.005 69.05
0.1
0.5
0.005
0.1
—
—
—
60.64
94.66
98.57
62.45
95.05
98.69
66.31
95.77
98.89
65.49
95.63
98.85
67.52
96.00
98.96
68.92
96.23
99.02
—
—
—
39.36
5.34
1.43
The physicochemical constants of the reactants (m.p., b.p.)
after purification corresponded to published data.5
10
15
20
25
30
30.95 37.55
Results and Discussion
96.25
99.05
—
—
—
3.75
0.95
—
—
—
4.95
1.31
33.69
4.22
It has previously2 been shown that Nꢀalkylated anilines
with an isostructural alkyl substituent are least reactive in
arylsulfonylation. For instance, in Nꢀisopropylaniline (1b)
the reaction center is screened by two Me groups, due to
which the attack to the nucleophilic center of amine by
the arylsulfonylating agent is hindered. We expected an
increase in the reactivity of this aliphaticꢀaromatic amine
in arylsulfonylation with a change in the solvent nature;
however, for the waterꢀalcoholic solvents under study with
the water content 5—50 wt.% hydrolysis occurred much
more rapidly than arylsulfonylation and, hence, it was
0.5
1.11
0.005 71.82
0.1
0.5
0.005
0.1
28.18 34.51
96.71
99.16
—
—
—
3.29
0.84
—
—
—
25.33 31.08
2.85
0.72
4.37
1.15
32.48
4.00
0.5
1.04
0.005 74.67
0.1
0.5
97.15
99.28
3.77
0.98

Arylsulfonylation of Nꢀalkylanilines
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 6, June, 2006
975
the increase reaches almost 5 times on going from neat
propanꢀ2ꢀol to a 30% aqueous solution (see Table 1).
The apparent activation parameters of the reaction of
amine 1с with sulfonyl chloride 2 in a 10% aqueous
the synthesis of the arylsulfonylation products of amines
1a,c in 98—99% yield.
This work was financially supported by the Ministry of
Education and Science of the Russian Federation (Grant
RNP.2.2.1.1.7181).
propanꢀ2ꢀol were estimated: Еа = 17.4 3.4 kJ mol–1
,
–∆S≠ = 216.6 11.4 J mol–1 K–1. Comparison of the obꢀ
tained results and data for the series of alkylarylamines
in pure propanꢀ2ꢀol2 (Еа = 17—30 kJ mol–1, ∆S≠
=
References
180—227 J mol–1 K–1) suggest that the mechanism of the
reaction under study remains unchanged upon this change
of the solvent.
1. T. P. Kustova, I. O. Sterlikova, and M. V. Klyuev, Izv. Akad.
Nauk, Ser. Khim., 2002, 2000 [Russ. Chem. Bull., Int. Ed.,
2002, 51, 2157].
2. T. P. Kustova, I. O. Sterlikova, and M. V. Klyuev, Zh. Obshch.
Khim., 2002, 72, 1330 [Russ. J. Gen. Chem., 2002, 72 (Engl.
Transl.)].
3. T. P. Kustova, L. V. Kuritsyn, and A. O. Sedova, Izv. Vuzov.
Khim. Khim. Tekhnologiya, 1998, 41, 44 [Izv. Vuz. Khim. Khim.
Tekhnol., 1998, 41 (Engl. Transl.)].
The yield of the arylsylfonylation product (αac) and
the content of 3ꢀnitrobenzenesulfonic acid admixture (αh)
in the binary solvents under study were calculated using
the kinetic data (see Table 1) by solving the system
of differential equations (3) and (4) using the fourthꢀ
order Runge—Kutta method.
4. L. V. Kuritsyn and N. K. Vorob´ev, Izv. Vuzov. Khim. Khim.
Tekhnologiya, 1969, 12, 1037 [Izv. Vuz. Khim. Khim. Tekhnol.,
1969, 12 (Engl. Transl.)].
5. Svoistva organicheskikh soedinenii. Spravochnik [Properties of
Organic Compounds. Reference Book], Ed. A. A. Potekhin,
Khimiya, Leningrad, 1984, 520 pp. (in Russian).
The results of calculations of αac and αh upon the
completion of the reaction of alkylarylamines 1a,c with
sulfonyl chloride 2 are presented in Table 2.
The data in Table 2 show that the water—propanꢀ2ꢀol
solvent with the water content 5—30 wt.% can be used in
Received January 10, 2006;
in revised form April 24, 2006