tric acid is a strong oxidizing agent.
Most metals dissolve to form nitrates
but with the evolution of nitrogen
oxides. Concentrated nitric acid also
reacts with several nonmetals to give
the oxo acid or oxide. Nitric acid is
generally stored in dark brown bot-
tles because of the photolytic decom-
position to dinitrogen tetroxide. See
also nitration.
nitric oxide See nitrogen monox-
ide.
nitridesCompounds of nitrogen
with a more electropositive element.
Boron nitride is a covalent compound
having macromolecular crystals. Cer-
tain electropositive elements, such as
lithium, magnesium, and calcium,
react directly with nitrogen to form
ionic nitrides containing the N3–ion.
Transition elements form a range of
interstitial nitrides (e.g. Mn 4 N, W 2 N),
which can be produced by heating
the metal in ammonia.
nitridingThe process of hardening
the surface of steel by producing a
layer of iron nitride. One technique
is to heat the metal in ammonia gas.
Another is to dip the hot metal in a
bath of molten sodium cyanide.
nitriÜcationA chemical process in
which nitrogen (mostly in the form
of ammonia) in plant and animal
wastes and dead remains is oxidized
atÜrst to nitrites and then to ni-
trates. These reactions are effected
mainly by the bacteria Nitrosomonas
and Nitrobacter respectively. Unlike
ammonia, nitrates are readily taken
up by plant roots; nitriÜcation is
therefore a crucial part of the *nitro-
gen cycle. Nitrogen-containing com-
pounds are often applied to soils
deÜcient in this element, as fertilizer.
Compare denitrification.
nitrile rubber A copolymer of
buta-1,3-diene and propenonitrile. Ni-
trile rubbers are commercially im-
portant synthetic rubbers because of
their resistance to oil and many sol-
vents. See also buna rubber.nitriles(cyanides)Organic com-
pounds containing the group –CN
bound to an organic group. Nitriles
are made by reaction between potas-
sium cyanide and haloalkanes in al-
coholic solution, e.g.
KCN + CH 3 Cl →CH 3 CN + KCl
An alternative method is dehydration
of amides
CH 3 CONH 2 – H 2 O →CH 3 CN
They can be hydrolysed to amides
and carboxylic acids and can be re-
duced to amines.
A- Information about IUPAC nomenclature
nitriteA salt or ester of nitrous
acid. The salts contain the dioxoni-
trate (III) ion, NO 2 – , which has a bond
angle of 115°.
nitroalkane (nitroparafÜn)A type
of organic compound of general for-
mula CnH 2 n+1NO 2 the nitroalkanes
are colourless, pleasant-smelling liq-
uids made by treating a haloalkane
with silver nitrate. They can be re-
duced to amines by the action of tin
and hydrochloric acid. Lower ni-
troalkanes such as nitromethane
(CH 3 NO 2 , b.p. 100°C) are used as
high-performance fuels (for internal
combustion engines and rockets), as
chemical intermediates, and as polar
solvents.
nitrobenzene A yellow oily liquid,
C 6 H 5 NO 2 ; r.d. 1.2; m.p. 6°C; b.p.
211 °C. It is made by the *nitration of
benzene using a mixture of nitric
and sulphuric acids.
nitrocellulose See cellulose ni-
trate.nitro compounds Organic com-
pounds containing the group –NO 2
(the nitro group) bound to a carbon373 nitro compounds
n