urbaf2

106 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

Titov [34] suggested in 1941 that nitrogen pentoxide undergoes a heterolytic

dissociation:

N 2 O 5 -> NO 2 + + NO 3 - (37)

It is the presence of the nitronium ion that accounts for the nitrating properties

of nitrogen pentoxide.

Ogg [98] studied the heat of dissolution of nitric anhydride is water, and on

the basis of the results obtained came to the conclusion that the compound under-

went the following reactions (a), (b), (c) and (d):

N 2 O 5 -> NO 3 + NO 2 (a)

NO 3 + NO 2 + N 2 O 5 (b)

NO 3 + NO 2 -> NO 2 + O 2 + NO (c)

NO + N 2 O 5 -> 3NO (^2) (d)
The (a) reaction corresponds to the reaction (37). Reaction (c) proceeds
slowly as compared with reaction (b), while, on the contrary, reaction (d) is
a fast one.
In general, the reaction of decomposition of N 2 O 5 , which is seemingly of the
first order (according to Smith and Daniels [99], Johnston and his co-workers
[100-102]), is in fact the resultant of reactions (a) and (b) and of the second order
reactions (c) and (d). Indeed, Johnston [100] found the decomposition of nitrogen
pentoxide in the presence of nitrogen dioxide to be a second order reaction.
In 1951, Titov and Shchitov [103] when examining the action of nitric anhydride
on normal paraffins and cycloparaffins, found that in the presence of an inert sol-
vent the reaction already started at 0°C, with the evolution of heat. Nitric acid
esters were formed in the reaction which, according to the authors, proceeded
through the following stages:
N 2 O 5 <-> .ONO 2 + .NO 2
RH + .ONO 2 -> R. + HONO 2 (38)
R. + .ONO 2 -> RONO 2
For example, from n-hexane, secondary n-hexyl alcohol nitrate was obtained:
(39)
n-Hexane 2-Hexyl 2-Hexyl nitrate
NO 2 formed in reaction (39) also reacted in accordance with (8) to give a nitro
compound along with an ester.
In reactions of N 2 O 5 with the olefins the products obtained had structures
that confirmed Titov’s view on the heterolytic decomposition of N 2 O 5 into NO 2 +
and NO 3

• . For example, when treating cyclohexene with nitrogen pentoxide, T. E.