urbaf2

AROMATIC NITRO COMPOUNDS 213

Owing to this, an acrydane, for example, can be converted under the influence

of m- dinitrobenzene or 1,3,5-trinitrobenzene into acridine in the presence of the

above mentioned radical :

(33)

In the presence of 2-cyano-2-propyl, using 0.72 mole of trinitrobenzene, acti-

dine can be obtained in 64% yield, whereas without the radical the yield is only 4%.

This reaction suggests that free radicals may act as reducing agents (Haines

and Waters [73]). Indeed, Inamoto and Simamura [74] have recently proved that

the 2-cyano-2-propyl radical can react with nitrobenzene to give small quantities

of O,N-di(2-cyano-2-propyl)-N-phenylhydroxylamine (I).

I

Thus it has been found that the free radical attacks the nitro group resulting in

its partial reduction. Apart from this acetone is also formed.

Jackson, Waters and Watson [75] found that the free benzyl radical (prepared

by the method reported by Beckwith and Waters [76] in 1957, which consists in

heating dibutylperoxide with toluene to the boiling point of the latter under

a nitrogen atmosphere) reacts with 1,3,5-trinitrobenzene, to form O,N-dibenzyl-

3,5-dinitrophenylhydroxylamine (II) in 28% yield. In addition to this, benzal-

dehyde was formed though it was never produced in the absence of trinitrobenzene.

The overall equation is:

C 6 H 3 (NO 2 ) 3 + 4C 6 H 5 CH 2 * -> II + C 6 H 5 CHO + C 6 H 5 CH 3 (34)

It follows from the above equation that one nitro group destroys four free

radicals. A further conclusion is that the complete reduction of a nitro group

to an amino group would destroy six free radicals.

Recently Eley and Parfitt [77] discovered that a,a’-diphenyl- β -picrylhydrazyl
(DPPH) (III) is one of the best organic semiconductors with an energy gap of

only 0.26 eV.