Modern inorganic chemistry

GROUPV 231

unstable compound sodium dioxodinitrate(I) (hyponitrite).

Na 2 N 2 O 2 [i.e. Naf+(NO~) 2 ] is formed. In addition to these

reactions covalent bonds are formed by electron sharing and

electron donation. Nitrogen monoxide, when it is absorbed by cold

aqueous iron(II) sulphate, forms the brown ion [Fe(NO) (H 2 O) 5 ]^2 "

in which one ligand molecule of water has been replaced by nitrogen

monoxide, the latter donating an electron pair.

Electrons are shared when nitrogen monoxide combines with

oxygen, a spontaneous reaction, to give nitrogen dioxide

2NO + O 2 -> 2NO 2

(Although this reaction is exothermic, the gas does not burn in air

or oxygen.)

A similar reaction occurs with chlorine, to give nitrosyl chloride

2NO + C1 2 -» 2NOC1

As might be expected for a +2 oxide, nitrogen monoxide can act
as both an oxidising and reducing agent. Oxygen oxidises it to NO 2
whilst more powerful oxidising agents such as acidified potassium
manganate(VII) solution oxidise it to nitric acid.
Reduction products vary depending on the reducing agent, for
example dinitrogen oxide is obtained with sulphurous acid, nitrogen
is obtained when the gas is passed over heated metals (e.g. copper
and iron) and ammonia is produced when the gas reacts with
aqueous chromium(II) salts.

NITROGEN DIOXIDE, NO 2 , AND DINITROGEN TETROXIDE. N 2 O 4

The structure of nitrogen dioxide contains an unpaired (odd)
electron and the molecule is consequently paramagnetic. The odd
electron is not localised on any atom and the structure can be best
represented as a resonance hybrid of the structures:

N N N N

S \ X ^ ^ \ / ^

(^00000 000) X X
Both N—O bonds are of equal length.
Unlike nitrogen monoxide, nitrogen dioxide has properties more
typical of an odd electron molecule. It is a coloured (brown), reactive
gas which dimerises to the diamagnetic colourless gas dinitrogen
tetroxide, N 2 O 4 , in which the odd electron is paired. The structure
of dinitrogen tetroxide can be represented as a resonance hybrid of: