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(^54) CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES
Here it is not water but sulphuric acid which is given off.
This view Michael confirmed in 1935 when he emphasized [2] that in a molecule
of nitric acid the dominating factor, which facilitated the reaction, was the affinity
of oxygen for hydrogen and of nitrogen for the aryl group.
Hence the facility of the transformation:
(3)
However, Giersbach and Kessler [3] supposed that the initial step in the nitration
reaction was the addition of two nitric acid molecules to a benzene molecule,
Experimental evidence of the possibility of the formation of products from
aromatic hydrocarbons by the addition of nitric acid was provided by Meisen-
heimer [4]. He found that with anthracene the nitric acid molecule attached itself
to the 9 and 10 carbons (of aliphatic character), yielding the product I, which in
the presence of sodium hydroxide or acetic anhydride gave off water to form meso-
nitroanthracene (II) :
(4)
It has also been found that certain aldehydes, ketones and carboxylic acids
esters form well defined products with nitric acid (Reddelien [5]). For example,
bemzaldehyde with 60% nitric acid gives a colourless, unstable oil, and cinna-
mic aldehyde forms fairly stable white crystals, melting at 60-61°C, with 65%
nitric acid. Acetophenone, benzophenone, fluorenone, phenanthrenoquinone
and camphor give similar addition products.
They are converted to nitro compounds under the influence of nitric acid or acetic
anhydride and are decomposed by water to give the initial components.
According to T. Urbanski and Hofman [5a] the ionic oxonium salt structure
can be attributed to these compounds: