urbaf2

NITRATION AND NITRATING AGENTS 25

The anhydrous nitric acid which is formed in this system is dissociated into the

same ions (eqn. (1) p. 6).

The diagram (Fig. 9) shows the concentration of NO 2 + ions in various nitrating

mixtures determined by measurements of the intensity of Raman lines. The limits

FIG. 9. Concentration NO 2 + ions in mixtures HNO 3 -H 2 SO 4 -H 2 O (Gillespie and

Millen [11]).

of the ability to nitrate nitrobenzene by various mixtures almost coincide with

the limit of detectability of NO 2 + by the Raman spectrum analysis.

According to Chédin and Fénéant [62a] the maximum concentration of NO 2 + (ca.

4.5 g-ion/l.) exists in the solution of 20-40% HNO 3 in sulphuric acid.

Structure of the nitronium (nitryl) ion NO 2 +

In 1941 Titov [35] considered the structure of the nitronium ion as a number

of resonating structures :

Titov postulated that the NO 2 + ion may be regarded as isosteric with carbon

dioxide O=C=O, thus suggesting a linear structure for the ion.