1070-4272/03/7611-1787$25.00C2003 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 76, No. 11, 2003, pp. 1787!1791. Translated from Zhurnal Prikladnoi Khimii, Vol. 76, No. 11,
2003, pp. 1837!1841.
Original Russian Text Copyright + 2003 by Polenov, Egorova, Ryazantseva.
AND INDUSTRIAL ORGANIC CHEMISTRY
Reduction of 4-Nitrosodiphenylamine with Sodium Hydroxy-
Yu. V. Polenov, E. V. Egorova, and S. G. Ryazantseva
Ivanovo State Chemical Engineering University, Ivanovo, Russia
Received March 13, 2003
Abstract-The kinetics of reduction of 4-nitrosodiphenylamine with sodium alkanesulfinates were studied,
and the reaction mechanism was suggested.
Reduction of 4-nitrosodiphenylamine (NDPA) to
4-aminodiphenylamine (ADPA) is of great practical
importance, since ADPA is an intermediate product in
preparation of antioxidants. In particular, condensation
of ADPA with acetone yields 4-isopropylaminodi-
phenylamine (commercial name Diafen FP) , which
is thermal stabilizer for polyethylene, polystyrene, and
synthetic rubber, inhibitor of tarring of motor fuel,
and stabilizer of leaded gasolines. In recent years,
derivatives of alkanesulfinic acids containing various
substituents at the first carbon atom were found to be
highly promising in reduction of organic nitro and
nitroso compounds. The feature of these compounds is
the presence of abnormally long C3S bond, which
under certain conditions ruptures to form active inter-
mediates having high reducing power: SO
radical anions . The use of
sodium hydroxymethylsulfinate as a reducing agent
allows preparation of ADPA from NDPA in almost
quantitative yield . The mechanism of this reaction
was thoroughly studied. It was shown that the initial
substance can be reduced both with sulfoxylate anions
and directly with hydroxymethanesulfinate molecules
. The absence of side reactions allows reliable
determination of the rate constants of the stages in-
volving decomposition of the reducing agent and the
reaction of sulfoxylate anions with the oxidant. These
parameters can be used for optimizing processes in-
volving such reducing agents.
In this connection, it is appropriate to study the
possibility of NDPA reduction with derivatives of
alkanesulfinic acids with the aim to compare their
reactivity and performance and also to elucidate the
NDPA was prepared by threefold recrystallization
of the commercial product from ethanol.
Sodium hydroxymethanesulfinate (SHMS), sodium
hydroxyethanesulfinate (SHES), and sodium amino-
methanesulfinate (SAMS) used as reducing agents
were prepared by the procedures described in [5, 6].
The concentrations of their solutions were determined
by iodometric titration .
NDPA was reduced directly in the colorimeter cell,
which was placed into a temperature-controlled jacket
connected to a UT-2 thermostat (the temperature was
maintained with the accuracy of +0.5oC). The reaction
rate was determined by measuring the optical density
of the NDPA solution at l = 400 nm, which corre-
sponds to the absorption maximum in its electronic
spectrum. It was found preliminarily that the reaction
products and the reducing agent do not absorb light at
this wavelength. The optical density was measured
on a KFK-2 spectrophotometer equipped with an
Shch-1516 digital dc voltmeter.
All kinetic measurements were carried out at more
than thousand-fold excess of the reducing agent,
which provides practically constant concentration of
the reducing agent in the course of the experiment.
Preliminary experiments showed that the reaction
of NDPA with SHMS in aqueous alkaline solution
yields a compound that can be isolated by distillation
in a vacuum at approximately 200oC. The melting
point of this compound is 66367oC, the half-wave
reduction potential on a dropping mercury electrode
= 30.23 V (anodic wave), and the appearance
of the product corresponds to published data for
ADPA [8, 9].
To determine the stoichiometry of the reaction
between SHMS and NDPA, we mixed the solutions of
these compounds in 1 M aqueous NaOH. The result-
ing mixture was kept under argon at 73oC until de-
colorization, after which the SHMS content was deter-