Kinetics of low-temperature oxidative chlorination of benzene in aqueous acetic acid

Article abstract of DOI:10.1007/s11176-005-0312-0

The kinetics of chlorination of benzene with a mixture of sodium peroxide with hydrochloric acid in aqueous acetic acid at 298 K was studied. The chlorination rate is the highest when the AcOH concentration in the binary solvent is 49.4-40.6 mol % and the ratio of the initial cocentrations of water and sodium peroxide, 18.5-20.2. The linear dependences of logk _app on the AcOH concentration and [H₂O]₀/[Na₂O ₂]₀ ratio were obtained. 2005 Pleiades Publishing, Inc.

Full text of DOI:10.1007/s11176-005-0312-0

Russian Journal of General Chemistry, Vol. 75, No. 5, 2005, pp. 748 750. Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 5, 2005,
pp. 792 794.
Original Russian Text Copyright
2005 by Rudakova, Erykalov.
Kinetics of Low-Temperature Oxidative Chlorination
of Benzene in Aqueous Acetic Acid
N. I. Rudakova and Yu. G. Erykalov
Ivanovo State University, Ivanovo, Russia
Received November 25, 2003
Abstract The kinetics of chlorination of benzene with a mixture of sodium peroxide with hydrochloric
acid in aqueous acetic acid at 298 K was studied. The chlorination rate is the highest when the AcOH con-
centration in the binary solvent is 49.4 40.6 mol % and the ratio of the initial cocentrations of water and
sodium peroxide, 18.5 20.2. The linear dependences of logkapp on the AcOH concentration and [H2O]0/
[Na2O2]0 ratio were obtained.
Arenes are usually chlorinated by a direct reaction
of molecular chlorine with an aromatic compound.
Another procedure used in production of chloroben-
zene is high-temperature oxidative chlorination of
benzene with chlorine generated by catalytic oxidation
of HCl with oxygen [1]. However, the low-tempera-
ture (at 273 353 K) oxidative halogenation with hy-
drohalic acids and hydrogen peroxide (or metal perox-
ides) is studied insufficiently. As shown in [2 9],
low-temperature halogenation allows preparation of
chloro- and bromotoluenes, monochloro-p-xylene,
1-bromonaphthalene, and other compounds in fairly
high yields without using toxic molecular halogens.
binary solvent AcOH H2O is decreased from 91.9 to
40.6 mol %, kapp increases (run nos. 1 7 in Table 1).
A similar trend was observed in chlorination with
molecular chlorine of benzene in trifluoroacetic acid
[11] and of toluene in acetic acid [12].
In the NAcOH range from 4.06 to 91.9 mol %,
linear correlation (1) is valid (r 0.989):
log kapp
=
(2.33 0.11)
(2.36 0.14)NAcOH/100. (1)
At NAcOH
40.6 mol %, the constants decrease,
and correlation (1) is no longer observed (Fig. 1).
Since, according to reactions (I) and (II), under
the experimental conditions [Na2O2]0 corresponds
to [Cl2]0 and the chlorinating power of the system
H2O2 HCl depends on the water concentration in the
reaction mixture, decreasing with an increase in [H2O]
[4], it could be expected that the ratio of the initial
H2O and Na2O2 concentrations q would affect the rate
constant more significantly than does the AcOH con-
centration in the binary solvent. Indeed, in run nos. 7
and 12 (Table 1), at virtually equal NAcOH (40.6 and
40.2 mol %), the rate constants are essentially differ-
ent. In run nos. 15 and 16, at equal q (40.6 and 40.7)
and different NAcOH (42.6 and 30.5 mol %), the con-
stants are virtually equal. The influence of the concen-
tration ratio q on the rate constant is seen from Fig. 2.
Taking into account the urgency of theoretical
studies of oxidative halogenation, in this study we
examined the solvent effect on the kinetics of the ben-
zene chlorination in the system Na2O2 HCl AcOH
H2O. The simplified scheme of the process includes
reactions (I) (III):
Na2O2 + 2HCl
H2O2 + 2HCl
C6H6 + Cl2
2NaCl + H2O2,
Cl2 + 2H2O,
(I)
(II)
C6H5Cl + HCl.
(III)
The experiment was performed at 298 K in aque-
ous AcOH of various concentrations. The reactant
ratio C6H6 : Na2O2 : HCl was 1 : 1 : (4 5). The ben-
zene chlorobenzene mixtures obtained were analyzed
by GLC. Preliminary experiments showed that, under
the experimental conditions, the yield of benzene
dichlorination products was insignificant.
The ascending and descending portions of the
logkapp q dependence can be described by Eqs. (2)
and (3), respectively:
log kapp = (0.075 0.005)q (4.932 0.065), r 0.989, (2)
log kapp = (0.059 0.002)q (2.010 0.093), r 0.997. (3)
As in [10], the reaction rate is satisfactorily de-
scribed by a second-order reaction equation. Table 1
shows that, as the AcOH concentration (NAcOH) in the
In the range of q from 18.5 to 21.1, the reaction
1070-3632/05/7505-0748 2005 Pleiades Publishing, Inc.

KINETICS OF LOW-TEMPERATURE OXIDATIVE CHLORINATION
749
1
2
2.0
1
2.0
1.5
1.5
2
3
1.0
0.5
1.0
0.5
0
0
50
N
100
AcOH, mol %
20
40
60
q
Fig. 2. Influence of the ratio q of the H O and Na O
2 2
2
Fig. 1. Influence of the AcOH concentration in the
concentrations on
k
: (1) experimental data and
app
binary solvent on k : (1) experimental data and (2)
(2, 3) results of calculations by Eqs. (2) and (3),
app
results of calculations by Eq. (1).
respectively.
rate is the highest, which is apparently due to the low-
est activation energy under these conditions (Table 2).
HCl + H2O
Cl2 + H2O
H3O+ + Cl ,
HOCl + HCl.
(4)
(5)
To explain why the logkapp q dependence passes
through a maximum, we can suggest that oxidative
chlorination of benzene under the experimental condi-
tions occurs with different limiting steps depending
on q and on AcOH content in the binary solvent. At
q < 18, in media with a high AcOH concentration, the
reaction occurs by a common mechanism of electro-
philic substitution [11, 12]. As the water concentration
is increased, at q > 20, dissociation of HCl apparently
starts to prevail, equilibria (4) and (5) are shifted to
the right, and the formation of the chlorinating agent
becomes the limiting step:
Our results allow us to formulate certain practical
recommendations concerning the synthesis of chloro-
benzene. In particular, in chlorination of benzene with
the system Na2O2 HCl AcOH H2O at 298 K, the
following conditions are the most favorable for the
formation of chlorobenzene: initial concentration ratio
[H2O]/[Na2O2] 18.5 21.1 and AcOH concentration in
the binary solvent 40.6 49.4 mol %. Under these
conditions, the chlorobenzene content in a mixture
with benzene is 65.1 70.3 wt % in 2 h.
EXPERIMENTAL
Table 1. Rate constants of oxidative chlorination of
benzene
The reaction mixtures were analyzed on an LKhM-
8MD chromatograph as described in [10]. The deter-
mination error was (2 3)%, as judged from the check
measurements with reference benzene chlorobenzene
mixtures.
Run
no.
NAcOH
mol%
,
kapp 104,
qa
1
kg mol 1 s
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
91.9
80.9
67.6
50.8
49.4
45.1
40.6
35.9
30.8
34.8
31.0
40.2
47.2
42.5
42.7
30.5
3.9
8.4
0.28 0.02
0.48 0.04
1.06 0.10
2.53 0.15
4.52 0.29
3.83 0.28
4.03 0.35
3.70 0.32
2.74 0.18
1.53 0.12
1.08 0.09
1.18 0.06
1.19 0.08
0.45 0.03
0.34 0.02
0.30 0.04
Benzene chlorination. To a temperature-controlled
(298 K) mixture of 0.02 mol of benzene, 7 cm3 of
12.8
17.3
18.5
19.3
20.2
21.1
22.2
27.3
31.3
31.3
31.3
36.2
40.6
40.7
Table 2. Rate constants and activation energies at
various q
kapp 104,
Ea,
kJ mol
q
T, K
1
1
kg mol 1 s
12.8
12.8
12.8
19.3
19.3
19.3
31.3
31.3
31.3
298
303
313
298
303
313
298
303
313
1.06 0.10
1.52 0.15
2.33 0.21
3.81 0.28
4.29 0.38
4.90 0.46
1.18 0.06
2.95 0.18
5.29 0.45
38.0
12.1
70.2
a
(q) Ratio of the initial concentrations of water and sodium
peroxide.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 75 No. 5 2005

750
RUDAKOVA, ERYKALOV
concentrated HCl ( 0.08 mol of HCl), and 1/3 of the
total volume of the solvent, we added with stirring
a solution of 0.02 mol of sodium peroxide in the
solvent (2/3 of the total volume). As solvent we used
glacial acetic acid and acetic anhydride. In most cases,
water was introduced with concentrated HCl, but in
some experiments additional H2O was introduced to
attain the required q. The total solvent volume was
varied from 10 to 25 cm3. From the reaction mixture,
at definite intervals, we took samples, from which we
extracted the organic layer; this layer was analyzed
by GLC. Benzene and acetic acid were purified as
described in [13]. The concentration of acetic acid was
monitored by alkalimetric titration. The content of the
main substance in sodium peroxide was determined
according to [14]. The other chemicals were of chemi-
cally pure or pure grade and were used without addi-
tional purification.
5. Kharchuk, V.G. and Kolenko, V.P., Abstracts of
Papers, I Vsesoyuznoe soveshchanie po khimicheskim
reaktivam (I All-Union Meet. on Chemicals), Ufa,
1985, p. 187.
6. Chalabiev, Ch.A., Abdullaev, D.K., and Sala-
khov, M.S., Neftekhimiya, 1989, vol. 29, no. 6, p. 786.
7. Rudakova, N.I., Anufrieva, O.V., and Smirnova, E.V.,
Zh. Obshch. Khim., 1992, vol. 62, no. 10, p. 2290.
8. Rudakova, N.I., Erykalov, Yu.G., Zharikova, S.M.,
Dmitrieva, E.V., and Mataradze, M.S., Zh. Obshch.
Khim., 1995, vol. 65, no. 2, p. 315.
9. Rudakova, N.I., Erykalov, Yu.G., Belousova, E.Yu.,
Soboleva, T.Yu., and Dobrova, A.V., Zh. Obshch.
Khim., 1995, vol. 65, no. 11, p. 1880.
10. Rudakova, N.I. and Erykalov, Yu.G., Zh. Obshch.
Khim., 1997, vol. 67, no. 11, p. 1876.
11. Himoe, A. and Stock, L.M., J. Am. Chem. Soc., 1969,
vol. 91, no. 12, p. 1452.
REFERENCES
12. Becker, H., Einfuhrung in die Elektronentheorie
organisch-chemischer Reaktionen, Berlin: Wissen-
schaften, 1964, 2nd ed. Translated under the title
Vvedenie v elektronnuyu teoriyu organicheskikh re-
aktsii, Moscow: Mir, 1977, pp. 497 501.
13. Gordon, A.J. and Ford, R.A., The Chemist’s Com-
panion. A Handbook of Practical Data, Techniques,
and References, New York: Wiley, 1972. Translated
under the title Sputnik khimika, Moscow: Mir, 1976,
pp. 437 446.
14. Siggia, S. and Hanna, J.G., Quantitative Organic
Analysis via Functional Groups, New York: Wiley
Interscience, 1979. Translated under the title Koli-
chestvennyi organicheskii analiz po funktsional’nym
gruppam, Moscow: Khimiya, 1983, pp. 263 264.
1. Efros, L.S. and Gorelik, M.V., Khimiya i tekhnologiya
promezhutochnykh produktov (Chemistry and Tech-
nology of Intermediates), Leningrad: Khimiya, 1980,
pp. 174 180.
2. Salakhov, M.S., Guseinov, M.M., Chalabiev, Ch.A.,
and Abdullaev, D.K., Neftekhimiya, 1974, vol. 14,
no. 3, p. 471.
3. Guseinov, M.M., Chalabiev, Ch.A., Abdullaev, D.K.,
and Salakhov, M.S., Neftekhimiya, 1983, vol. 23,
no. 5, p. 659.
4. Muganlinskii, F.F. and Guseinov, M.M., Zh. Vses.
Khim. O va. im. D.I. Mendeleeva, 1985, vol. 30,
no. 3, p. 100.
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