urbaf2

102 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

Nitrolic acids (II) are relatively stable when R is alkyl but can lose nitrous

acid with furoxane (IV) formation (Wieland and Semper [14]). Aci-nitroparaffins (III)

readily yield aldehydes when R is alkyl. At lower temperatures the product

V (R=C 6 H 5 ) predominates.

According to Ponzio [35], benzaldoxime can form phenyl-gem-dinitromethane

C 6 H 5 CH(NO 2 ) 2 , under the action of N 2 O 4.

NITRATION WITH NITROGEN DIOXIDE IN THE PRESENCE

OF SULPHURIC ACID

Pinck [88] studied the nitrating action of nitrogen dioxide in a sulphuric acid

solution. According to this author, the nitrating action of the solution proceeds

as follows, from each N 2 O 4 molecule with the formation of one molecule of HNO 3

and one of nitrosylsulphuric acid:

(27)

When treating 1 mole of toluene with 1.05 mole of N 2 O 4 in the presence of

1.6 moles of 95 % sulphuric acid at 50-55°C for 3½ hr, the yield of nitrotoluene

obtained amounted to 87.5% of theory.

According to Battegay [58], nitration with nitrogen dioxide in the presence

of sulphuric acid followed a course such that an addition product of H 2 SO 4 and

the aromatic hydrocarbon was formed initially. Battegay assumed the sulphuric

acid activated the aromatic ring in a way similar to the role of aluminium or fer-

ric chlorides in the Friedel-Crafts reaction, or as in a chlorination reaction. Indeed,

Battegay found that benzene may be readily chlorinated in the presence of sul-

phuric acid instead of FeCl 3.

Benzene activated with sulphuric acid would add on to N 2 O 4 which, according

to Battegay, has the structure of “nitrosyl nitrate” NO 2 .ONO. An addition prod-

uct was thought to be formed which, in the presence of an excess of sulphuric

acid, would decompose to yield a nitro compound and nitrosylsulphuric acid.

C 6 H 6 + NO 2 + H 2 SO 4 -> C 6 H 5 NO 2 +NSO 5 H + H 2 O (28)

Titov and his co-workers [34] proposed the following mechanism of nitra-
tion of aromatic compounds with nitrogen dioxide in the presence of sulphuric

acid:

RH + N 2 O 4 -> RNO 2 + HNO 2

N 2 O 4 + H 2 SO 4 <-> HNO 3 + NSO 5 H

2NSO 5 H + H 2 O <-> N 2 O 3 + 2H 2 SO 4

(a)

(b)

(c)