urbaf2

NITRATION THEORIES^67

Gillespie and Millen [31] believed that sulphuric acid in an intermediate addi-
tion product is linked to the carbonyl group by a hydrogen bond:

K. Lauer [62] obtained the results (given in Table 5) by nitrating aniline and

anilides with nitric and with mixtures of nitric and sulphuric or acetic acids at

20°C, over 24 hr.
It can be seen from the results referred to and also from the earlier data of
Holleman and his co-workers [53] that aniline acylation has a decisive influence
on the orientation of the nitro group.
When nitrating p- cresol, Holleman [51] found that according to whether p- cresol

was reacted alone or as the p- cresol carbonic ester different isomers were

obtained (Table 6).

TABLE 6

Nitrated compound

Composition of the product

% 2-nitro % 3-nitro

p- Cresol trace close to 100

p- Cresyl carbonate 96.3 3.7

Holleman compared the data obtained by Pictet and Khotinsky [63] in the

nitration of toluene with acetyl nitrate with those obtained by other authors in the

nitration of toluene with a conventional nitrating mixture. The results are tabula-

ted below (Table 7).

TABLE 7

Nitrating agent

Composition of the nitration product

% ortho- % para-

Acetyl nitrate^8812

Nitric and sulphuric acid

mixture 55 40

Martinsen [64] in his studies on nitration kinetics determined the influence of

substituents on the rate of the reaction. He classified them according to their

influence on the reaction rate, comparing it with that of chlorine, which in some

cases (as compared with hydrogen) can lower, while in others raise the rate:

NO 2 >SO 3 H>COOH>Cl<CH 3 <OCH 3 <OC 2 H 5 <OH

decreasing increasing

the reaction rate the reaction rate

It is interesting to know that the substituents which decrease the reaction rate

direct towards the meta position while those increasing it direct towards the ortho
and para positions.