1070-4272/05/7802-0315 + 2005 Pleiades Publishing, Inc.
Russian Journal of Applied Chemistry, Vol. 78, No. 2, 2005, pp. 315!318. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 2, 2005,
Original Russian Text Copyright + 2005 by Klyuchnikov, Chachkov, Deberdeev, Zaikov.
AND POLYMERIC MATERIALS
Mechanism of Depolymerization of Polymeric
p-Dinitrosobenzene in Vulcanization of Unsaturated Rubbers:
A Quantum-Chemical Study
O. R. Klyuchnikov, D. V. Chachkov, R. Ya. Deberdeev, and G. E. Zaikov
Kazan State University of Power Engineering, Kazan, Tatarstan, Russia
Kazan State Technological University, Kazan, Tatarstan, Russia
Emanuel’ Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, Russia
Received June 1, 2004
Abstract-The mechanism of depolymerization of polymeric p-dinitrosobenzene in vulcanization of un-
saturated rubbers is analyzed. The results obtained explain why the vulcanizing activity of p-dinitrosobenzene
decreases in the course of its prolonged storage.
p-Dinitrosobenzene (DNB) is a component of rub-
ber3substrate adhesion systems  and a low-tem-
perature vulcanizing agent for stocks based on un-
saturated rubbers . DNB is a polymeric compound
virtually insoluble under common conditions in any
The vulcanizing activity of DNB is known to
change in the course of its storage [4, 5]; this fact
calls for theoretical substantiation. Furthermore, data
on the structure of polymeric p-dinitrosobenzene
(poly-DNB) are contradictory, and nothing is known
about the mechanism of its depolymerization in
the course of addition to unsaturated compounds
(in particular, in vulcanization of unsaturated rub-
In the papers concerning the kinetics and mechanism
of addition of poly-DNB to unsaturated compounds
[6, 7], the authors, as a rule, presented the monomeric
DNB structure; some authors assumed the structure
has a dimeric sandwich form (Fig. 1) , but this
structure does not stand up to criticism.
It is known that IR spectra of poly-DNB contain
a strong band at 1264 cm
[10, 11], characteristic
of nitrosoarene trans dimers [10, 12], with a C3N3N
angle in the sandwich structure close to 120o.At
the same time, the C3N3N angle in the sandwich
structure is close to 90o, and, therefore, this structure
should be strained and thermodynamically unstable.
Experimental determination of the poly-DNB struc-
ture is complicated by its high dispersity and insolu-
bility in all the solvents under common conditions.
Therefore, to study the geometry of poly-DNB and
energy effects of its reactions, we used quantum-
chemical calculations. We chose the relatively reli-
able DFT B3LYP method with the 6-31G(d) basis set.
The calculations were performed with a computer
cluster of the Kazan State Technological University,
using the GAUSSIAN 98 program package , with
full geometry optimization. For the model structures,
we calculated the force constants, vibration frequen-
cies, thermodynamic quantities, and variation of the
relative energy in extension of the (O)N3N`(O`) bond
of model structures. To reduce the number of basis
functions, we used 2-butene and 2-pentene as struc-
tures modeling a fragment of an unsaturated rubber.
Fig. 1. Presumed dimeric sandwich structure of DNB.