84 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVESCycle-polymethylenic hydrocarbons can also be nitrated with dilute nitric
acid (e.g. Wichterle [15a]).
Grundman and Haldenwanger [70] nitrated cyclohexane with nitric acid (34%
HNO 3 ) at 122°C under 4 atm pressure. Nitrocyclohexane and gem-dinitrocyclo-
hexane (I) resulted (m. p. 218ºC).Aromatic hydrocarbons, e.g. benzene, are not nitrated with dilute nitric acid.
On the contrary, olefins can readily be nitrated to nitroolefins by means of
12.5% nitric acid as shown by Konovalov [15].
The tertiary carbon (>CH) is nitrated most readily, the secondary one (-CH 2 )
with some difficulty, and the primary one (-CH 3 ) with greater difficulty. Oxi-
dation products, as for example acids, are formed along with nitro compounds.
These classical studies were continued by Markovnikov [16] in 1898 and Nametkin
[17] in 1908. The principal conclusions of Nametkin are:
(1) Within certain limits the nitration yield does not depend on the concentra-
tion of nitric acid, but on the quantity of the acid; for example, the same yields
are obtained with 47.5% nitric acid (sp. gr. 1.3) as with 13.5% nitric acid (sp.
gr. 1.075).
(2) The nitration rate depends on temperature, pressure and the concentration
of the acid. The higher the temperature and pressure and the stronger the acid,
the higher the reaction rate.
(3) The quantity of nitric acid used for nitration affects the direction of the
reaction. A long run treating with an excess of nitric acid at a high temperature
enhances the formation of oxidation products.
Nametkin presents the nitration mechanism as follows:(5)(6)The author believes the labile forms with the -C=N bond are obtained as
intermediates and subsequently they isomerize to form nitro compounds.
Phenols can be nitrated with very dilute nitric acid. Thus, Cumming, Hopper
and Wheeler [18] reported that phenol can be converted into nitrophenol by