1070-4272/03/7607-1076$25.00C 2003 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 76, No. 7, 2003, pp. 1076!1078. Translated from Zhurnal Prikladnoi Khimii, Vol. 76, No. 7,
2003, pp. 1109!1111.
Original Russian Text Copyright + 2003 by Islamgulova, Tomilov, Akhmerova, Gil’mkhanova, Sapozhnikov.
AND CORROSION PROTECTION OF METALS
Electrochemical Synthesis of 2,5-Dichloroaniline
V. R. Islamgulova, A. P. Tomilov, S. G. Akhmerova,
V. T. Gil’mkhanova, and Yu. E. Sapozhnikov
Research and Technological Institute of Herbicides and Plant Growth Regulators, Ufa, Bashkortostan, Russia
State Research Institute of Organic Chemistry and Technology, Moscow, Russia
Received February 26, 2003
Abstract-A procedure was proposed for electrochemical reduction of 2,5-dichloronitrobenzene to 2,5-di-
chloroaniline in aqueous-ethanolic solution of sulfuric acid. The procedure for preparing 2,5-dichloroanilinium
sulfate was optimized. The influence exerted by the cathode material, nature and amount of the organic
solvent, sulfuric acid concentration, and electrolysis temperature on the yield and quality of the target product
2,5-Dichloroaniline (2,5-DCA) is an intermediate
in synthesis of pesticides. The existing methods of
reduction of nitro compounds with metals do not meet
modern environmental requirements, because the aris-
ing wastes are difficult to utilize. Therefore, electro-
chemical reduction of aromatic nitro compounds at-
tracts much attention . However, we found no
data on cathodic reduction of 2,5-dichloronitrobenzene
(2,5-DCNB) to 2,5-DCA. This process was the sub-
ject of the present study.
We tested two procedres for electrochemical reduc-
tion of 2,5-DCNB: a classical procedure based on
electroreduction of the nitro compound in a sulfuric
acid medium, yielding the amine in the salt form, and
a recently suggested procedure of reduction in a two-
phase system  involving the use of a solvent im-
miscible with water and a buffer solution with the pH
close to pK of the forming amine. The second proce-
dure allows preparation of the free amine in one step.
Classical reduction was performed in aqueous sol-
furic acid with addition of an organic solvent miscible
with water to obtain a homogeneous solution.
The first series of experiments on choosing the op-
timal cathode material was performed in an aqueous-
alcoholic solution of sulfuric acid at a cathodic current
density of 750 A m
and temperature of 48350oC.
The catholyte had the following composition (wt %):
2,5-DNCB 7.6, H
7.0, and C
Table 1 shows that the chemical yield of reduction
of 2,5-DCNB to 2,5-DCA on copper is low (69%).
The reduction on brass and nickel is also inefficient.
Addition of an Sn(II) salt has no appreciable effect on
the 2,5-DCA yield, whereas in the presence of zinc
sulfate the yield of 2,5-DCA based on 2,5-DCNB in-
creases to 87%. Reproducibly high yield of 2,5-DCA
(up to 88%) was obtained on a lead cathode in an
aqueous-ethanolic solution of sulfuric acid.
Then, using the lead cathode, we examined how
the 2,5-DCA yield depends on the nature and amount
of the organic solvent and on the concentrations of
2,5-DCNB and sulfuric acd. We found (Table 2) that
such solvents as acetone and acetonitrile affect the
reaction negatively. This is manifested in the de-
creased yield of 2,5-DCA (3.63 6.0%) as compared
to reduction in water without organic solvent added
(39%). Apparently, these solvents prevent adsorption
of 2,5-DCNB on the cathode. Addition of about
50 wt % of aliphatic alcohol increases the yield of
2,5-DCA to 88.4388.9%.
Variation of the 2,5-DCNB concentration in the
reaction mixture from 5.5 to 10% has virtually no
Table 1. Influence of the cathode material on the yield of
the reaction products
Cathode ³ 2,5-DCA yield based on 2,5-DCNB, %
Cu ³ 69.0
Cu* ³ 71.0
Cu** ³ 87.1
Brass ³ 63.0
Ni ³ 58.0
Pb ³ 88.0
Pb + 4%Sb ³ 80.0
added to 0.1 M concentration.
added to 0.1 M concentration.