Page 151 - Arrow Pushing in Inorganic Chemistry A Logical Approach to the Chemistry of the Main Group Elements

5A.2 SOME COMMON NITROGEN ELECTROPHILES: OXIDES, OXOACIDS, AND OXOANIONS 131
Under anhydrous conditions, ammonia acts as a nucleophile toward Cl , giving successively
2
NH Cl, NHCl , and NCl , as shown below:
2
2
3
−
Cl
H Cl
H Cl − CHl
N Cl Cl N + N
H H
H H H H (5A.3)
Cl Cl Cl
N Cl Cl N N
H H Cl
H Cl Cl

Chloramine (NH Cl) is increasingly used as a disinfectant in swimming pools. It persists
2
longer than molecular chlorine and has a much lower tendency to generate carcinogenic
chlorocarbons such as CHCl and CCl . Chloramine does, however, produce traces of nitro-
3
4
gen trichloride (NCl , also known as trichloramine), which has been linked to childhood
3
asthma.

REVIEW PROBLEM 5A.1

NBr exists but is very reactive (indeed explosive) and has been prepared at very low
3
∘
temperatures (∼–100 C) via the following reaction:
(Me Si) NBr + 2BrCl → NBr + 2Me SiCl
3
3
2
3
Suggest a mechanism.

5A.2 SOME COMMON NITROGEN ELECTROPHILES: OXIDES, OXOACIDS,
AND OXOANIONS

A fair number of nitrogen electrophiles are known. Many of these are nitrogen-oxo species,
+
+
for example, N O ,N O ,NO ,NO , and so on, where the higher electronegativity of
2 3 2 5 2
oxygen implies that the nitrogen atoms are the positive ends of dipoles and therefore also
the sites of attack by nucleophiles.
The two oxides N O and N O are classic acidic oxides; on exposure to water, they
2 3 2 5
hydrolyze immediately to nitrous acid (HNO ) and nitric acid (HNO ), respectively:
2 3
N O + H O = 2 HNO 2 (5A.4)
2
3
2
N O + H O = 2 HNO 3 (5A.5)
2
5
2