NITRATION AGENTS AND METHODS MORE RARELY USED^115group. This was shown by Ogata and Tsuchida [40] by means of the following
reaction:(57)It is rather important to note that if an aromatic nitro compound is the sub-
stance being nitrated, addition of mercuric nitrate to the nitric acid has no effect
on the reaction. For example, nitrobenzene is nitrated to dinitrobezene in the
same yield both in the presence of a mercury salt and in its absence. This can be
explained by the fact that nitro compounds such as nitrobenzene do not yield
addition product with mercuric salts.
Wright and his co-workers [141] found mercury plus a small amount of alumi-
nium (ca. 2%) and manganese (ca. 5%) to be a more efficient catalyst than mercury
alone. The experiments have shown that mercury increases the reaction rate while
manganese, though it has no influence on the principal reaction, assists in the
complete oxidation of oxalic acid which would otherwise contaminate the reaction
product.
It is of interest to point out the observation of the above authors that addition
of copper and especially vanadium inhibits the reaction.
McKie [142] found the yield of the nitration product to be higher when mercu-
ric nitrate was present in nitric acid. Thus for example, phenanthrene, when ni-
trated with anhydrous nitric acid in the presence of Hg(NO 3 ) 2 , gave nitrophenan-
threne in a yield higher by 13% than when nitric acid alone had been used.
Likewise the yields of nitro derivatives of phenol and α− naphthol could be in-
creased by addition of mercuric nitrate to dilute nitric acid.
Numerous industrial studies have been carried out to investigate the possi-
bility of using the oxynitration method for the commercial production of picric
acid. However, they have failed to provide a reliable method for industrial appli-cation. Particulars on some experiments on the industrial scale are dealt with in
the chapter on nitro derivatives of phenol.
NITRATING MIXTURES WITH STRONG OXIDIZING AGENTS
T. Urbanski, Semenczuk et al. [143] developed a method of “nitroxidation”
that consists in nitrating an aromatic hydrocarbon which contain an aliphatic
side chain, using nitrating mixtures containing strongly oxidizing agents, such
as CrO 3.
Toluene can be nitrated to yield p- nitrobenzoic acid and p- nitrotoluene to yield
2,4-dinitrobenzoic acid :