Kinetics of arylsulfonation of aminobenzoic acids with m-and p-nitrobenzenesulfonyl chlorides in the system water-2-propanol

Article abstract of DOI:10.1023/A:1012351722560

The concentrations of the uncharged and anionic forms of m-and p-aminobenzoic acids participating in arylsulfonation of the acids with m-and p-nitrobenzenesulfonyl chlorides in the system water-2-propanol at 298 K at various water contents and pHs were estimated. The resulting data were used to estimate the rate constants for the reactions of the above forms with nitrobenzenesulfonyl chlorides, based on experimental kinetic data.

Full text of DOI:10.1023/A:1012351722560

Russian Journal of General Chemistry, Vol. 71, No. 4, 2001, pp. 623 626. Translated from Zhurnal Obshchei Khimii, Vol. 71, No. 4, 2001,
pp. 668 671.
Original Russian Text Copyright
2001 by Kustova, Kuritsyn, Khripkova.
Kinetics of Arylsulfonation of Aminobenzoic Acids
with m-and p-Nitrobenzenesulfonyl Chlorides
in the System Water 2-Propanol
T. P. Kustova, L. V. Kuritsyn, and L. N. Khripkova
Ivanovo State University, Ivanovo, Russia
Received September 13, 1999
Abstract The concentrations of the uncharged and anionic forms of m- and p-aminobenzoic acids participat-
ing in arylsulfonation of the acids with m- and p-nitrobenzenesulfonyl chlorides in the system water 2-
propanol at 298 K at various water contents and pHs were estimated. The resulting data were used to estimate
the rate constants for the reactions of the above forms with nitrobenzenesulfonyl chlorides, based on experi-
mental kinetic data.
Kalinina and Kuritsyn [1, 2] previously studied the
kinetics of acylation of isomeric benzoyl chloride in
the system water dioxane and determined the rate
constants of reactions of the anionic and uncharged
forms of m- and p-aminobenzoic acids with benzoyl
chlorides. The kinetics of reaction of aminobenzoic
acids with arenesulfonyl chlorides have not yet been
studied. This is associated with some objective dif-
ficulties, including, first, moderate reactivity of arene-
sulfonyl chlorides toward arylamines [3 5] and,
second, the necessity of carefully controlling pH
which affects not only the ratio of ionic forms of the
amino acids, but also the rate of hydrolysis of the
arenesulfonyl chlorides [6].
At the same time, to know the kinetics of this re-
action is important for polymer chemistry [7] and for
fundamental kinetic studies on amino acid reactions.
In the present work we set ourselves the task to
study the kinetics of arylsulfonation o-, m-, and p-
aminobenzoic acids (Ia Ic) with m- and p-nitro-
benzenesulfonyl chlorides (IIa, IIb) in water 2-pro-
panol mixtures at 298 K.
In water and aqueous organic solvents, amino acids
Ia Ic can be present in the nonionized and various
ionized forms [scheme (1)]:.
K 3
K 1
+NH3C6H4COO
+ NH3C6H4COOH
K
(1)
NH2C6H4COO .
K 4
K 2
NH2C6H4COOH
Here K, K1, K2, K3, and K4 are the equilibrium
constants.
NH2C6H4COO + NO2C6H4SO2Cl
O COC6H4NHSO2C6H4NO2 + HCl.
(3)
It is known [8] that arenesulfonyl chlorides can
react only with nonprotonated amino group. Therefore,
the reaction of amino acids Ia Ic with sulfonyl
chlorides IIa, IIb in the system water 2-propanol
occurs by two concurrent directions [schemes (2)
and (3)]:
Moreover, in aqueous 2-propanol, along with arene-
sulfonation of amino acids Ia Ic, hydrolysis of sul-
fonyl chlorides IIa, IIb takes place [scheme (4)]:
NO2C6H4SO2Cl + H2O
NO2C6H4SO3H + HCl. (4)
The variation in the concentration of sulfonyl chlo-
rides IIa, IIb (cs) in the course of reactions (2) (4)
is described by Eq. (5):
NH2C6H4COOH + NO2C6H4SO2Cl
(2)
COOHC6H4NHSO2C6H4NO2 + HCl,
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624
KUSTOVA et al.
Table 1. Rate constants kapp, kh, and k
Ic, and kapp is the apparent rate constant of the reac-
tion.
cH O
wt%
,
c 0I 102, kapp 103,
kh 103,
k 102,
2
The kinetics of the reaction of amino acids Ia Ic
1
1
1
M
s
s
l mol 1 s
with sulfonyl chlorides IIa, IIb were studied follow-
ing the concentration of arenesulfonyl chloride by the
spectrophotometric indicator technique [9]. The indi-
cator used was lithium 2,6-dinitrophenolate. The
apparate rate constant kapp was calculated by the
Guggenheim equation (8):
Ia + IIb
9.48
19.69
29.74
39.89
49.91
60.81
69.59
4.00
4.01
4.00
3.99
4.00
4.01
4.00
0.44 0.03
0.83 0.06
1.23 0.01
1.39 0.01
1.65 0.01
2.77 0.03 10.75 0.10
5.87 0.05 11.90 0.01
Ib + IIa
3.40 0.13
5.05 0.01
6.50 0.01
7.60 0.03
9.40 0.07
0.25
0.81
1.45
1.58
1.77
4.23
11.70
kapp
lnln (T1/T2) = ln [T /T0(1
e
)]
kapp 1. (8)
Here T1 and T2 are transmission coefficients of the
reaction mixture at times and = = + , and T0
1
1
19.63
29.90
40.16
51.02
60.38
69.45
4.99
5.00
4.99
4.99
5.00
5.00
5.59 0.12
8.96 0.21
12.51 0.50
17.10 0.80
20.23 0.81
41.61 0.90
3.33
4.25
5.00
6.20
6.96
7.84
10.52
17.07
24.03
33.35
39.07
81.65
and T are the transmission coef2ficients of the solu-
tion before and after the reaction. The errors in kapp
were calculated at a confidence level of 0.95, the
random error in kapp was no higher than 2 3%.
Table 1 lists the kapp and kh values taken from
[10, 11], as well as k = (kapp
kh)/c0I.
Ic + IIb
9.48
19.69
29.74
39.89
49.91
60.81
69.59
4.01
4.00
4.00
4.01
4.00
4.00
3.99
0.98 0.23
1.13 0.14
1.29 0.18
1.71 0.11
2.41 0.06
3.40 0.13
5.05 0.01
6.50 0.01
7.60 0.03
9.40 0.07
1.60
1.56
1.60
2.37
3.67
6.49
14.00
As follows from Table 1, the reactivity of the amino
acids increases in the order Ia < Ic < Ib. The same
reactivity orders are characteristic of other monosub-
stituted anilines, such as toluidines and chloroanilines
[12, 13]. Table 1 shows that as the fraction of water
is increased from 20 to 70 wt%, the arylsulfonylation
rate constants of amino acids Ia Ic increase, on
average, by an order of magnitude. The increase in
the rate constants of the reaction of amino acids Ia Ic
with sulfonyl chlorides IIa, IIb with increasing frac-
tion of water in the reaction medium can be explained
by specific solvation of the reagents and transition
state and also by a change in the structure of the sys-
tem water 2-propanol.
3.67 0.09 10.75 0.10
6.79 0.28 11.90 0.01
dcs/d = k0 cI0cs + k cI cs + kh cs.
(5)
Here k0, k , and kh are the rate constans of reactions
(2) (4), respectively, and cI0 and cI are the current
concentrations of the uncharged and anionic forms of
amino acids Ia Ic.
We considered it interesting to compare experi-
mental and calculated k values. In this connection,
based of thermodynamic data for dissociation of
amino acids Ib, Ic and using the scheme of ionic
equilibria (1), we estimated the fractions of the ani-
onic and neutral forms of amino acids Ib, Ic by
Eqs. (9) and (10):
In view of the occurrence of the concurrent reac-
tions (2) and (3), the overall rate constant of the reac-
tion of amino acids Ia Ic with sulfonyl chlorides IIa,
IIb (k) can be represented by Eq. (6):
k = k0
+ k
.
(6)
0
Here
and
are the fractions of the uncharged and
1
1
1
= K3 cH1+ /(1 + K3 cH+ + K3 K4 + K21 K3K4 cH+), (9)
anionic0 forms of amino acids Ia Ic in the solution.
On condition that amino acids Ia Ic are present in a
considerable excess (102 103 times) compared with
arenesulfonyl chlorides IIa, IIb and with account for
Eq. (6), we can write Eq. (5) in form (7):
1
1
1
= K3 K4 /(1 + K3 cH+ + K3 K4
0
(10)
+ K21 K3 K41 cH ).
+
It should be noted that the equilibrium constants
K1, K2, K3, and K4 are related to the dissociation
constants K(1) and K(2), determined by acid and base
titration [14], by Eqs. (11) and (12):
dcs/d = (k0 c0I
+ k c0I
+ kh)cs = (k c0I + kh)cs
0
= kapp cs.
(7)
Here c0I is the initial concentration of amino acid Ia
K(1) = K1 + K2,
(11)
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 4 2001

KINETICS OF ARYLSULFONATION OF AMINOBENZOIC ACIDS
625
1
1
1
K(2) = K3 + K4 .
(12)
Table 2. pH of working solutions and
amino acids Ib and Ic
and 0 values for
From scheme (1) that includes equilibria between
uncharged and charged forms of amino acids Ia Ic
we can obtain Eq. (13):
c
H O, wt%
pH
0
2
Ib
Ic
K1 K3 = K2 K4.
(13)
40.16
51.02
60.38
69.45
4.6
5.0
5.2
5.85
0.429
0.658
0.754
0.932
0.350
0.214
0.155
0.049
However, three equations are insufficient for cal-
culating four rate constants. The fourth equation can
be obtained having determined K2 by the Hammett
equation, which is possible with acids Ib and Ic from
data for the reaction series: C6H5NH3+
39.89
49.91
60.81
69.59
3.5
3.85
4.0
4.4
0.070
0.147
0.196
0.380
0.248
0.230
0.218
0.168
C6H5NH2 + H+ [14]. All thermodynamic equilibrium
constants K1 K4 and dissociation constants K(1) and
K(2) for compounds Ib and Ic, required for estimation
of
and 0, were taken from [14] for water.
To estimate and 0, we were also to measure
As seen from Table 3, the rate constants calculated
pH in the working solution. To this end, we applied
potentiometric titration. The measured pH values for
working solutions of amino acids Ib, Ic, as well as
the fractions of the anionic and uncharged forms of
the acids, estimated by Eqs. (9) and (10), are listed
in Table 2.
by Eq. (6) fit closely the corresponding experimental
values for arylsulfonation of amino acids Ib, Ic in
aqueous 2-propanol containing 40 70 wt% of water.
The dependences of the rate constants for the aryl-
sulfonation of Ib, Ic (calculated and experimental) on
the composition of the system water 2-propanol are
given in Fig. 2.
Rigorous pH control is needed for two reasons.
First, at pH > 7 hydrolysis of arenesulfonyl chlorides
IIa, IIb is strongly enhanced, and, second, the con-
centration of H+ ions affects the fraction of the ionic
form of the amino acids, involved in arylsulfonation.
The dependence of the rate constants of the reaction
of amino acids Ib, Ic with sulfonyl chlorides IIa, IIb
on the pH of the medium is given in Fig. 1 for the
system water (30 wt%) ethanol. As seen from Fig. 1,
the arylsulfonation rate constant is much pH-depen-
dent, and in going from pH 1 to pH 6 it changes by
two (Ic) or four (Ib) orders of magnitude.
EXPERIMENTAL
Amino acids Ia Ic (pure grade) were recrystallized
from water. m-Nitrobenzenesulfonyl chloride (pure
grade) was recrystallized from hexane. p-Nitrobenzene-
sulfonyl chloride was synthesized by the procedure
[15] and recrystallized from benzene. Lithium 2,6-di-
nitrophenolate was synthesized from the correspond-
ing dinitrophenol. Perchloric acid (analytical grade)
was used as received. 2-Propanol (analytical grade)
The k and k0 values for amino acids Ib, Ic can be
determined by the correlation equation (14) taken
from [5].
pH
7
5
1
log k = 1.16 2.15 + 1.09 + 1.00S 0.89
2
+ 0.5
S
0.18 S
0.90
S.
(14)
Here
and are the substituent constants for aryl-
3
1
amine and arenesulfonyl chloride, respectively, S is
the solvent parameter (for 2-propanol, S = 0.17).
The k and k0 values, l mol 1 s , are 5.51 10 and
1
1
2
1
3
3.07 10 (Ib) and 3.48 10 and 3.15 10 (Ic),
1
3
log kr
respectively.
Table 3 lists the rate constants for the reaction of
amino acids Ib, Ic with sulfonyl chlorides IIa, IIb in
the system water 2-propanol, calculated by Eq. (6)
(kc) and experimental (ke).
Fig. 1. Dependendence of the logarithm of the rate
constant k of the reactions (1) Ib + IIa and (2) Ic + IIb
e
on the pH of the medium in the solvent water (30 wt%)
ethanol.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 4 2001

626
KUSTOVA et al.
meter operated in the millivoltmeter mode. The elec-
trodes were calibrated against HClO4.
8
1
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cH O
wt%
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kc
ke
kc
ke
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0.247
0.369
0.420
0.637
0.240
0.334
0.391
0.817
0.025
0.052
0.069
0.133
0.024
0.037
0.065
0.140
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RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 4 2001