Environmental Engineering Reference
In-Depth Information
Azido compounds are chemically active. After being illuminated or heated, they
decompose to azenes, which are very reactive. Most of azido compounds are
explosive, which should be used with caution. The reactions of halogenerated
hydrocarbons, aryl chlorides, or diazonium salts with sodium azide, or the reactions
of acrylhydrazines with nitrous acid, produce corresponding azido compounds.
Azido compounds are reagents for organic synthesis. Lead azide is the most
important composition of propellants in industry.
The terminal carbon of organic azido compounds is nucleophilic. Most azido
compounds are unstable and release N
2
gas. Curtius rearrangement has the inter-
mediate acyl azide in the reaction. Some azido compounds are 1,3-dipoles, which
are used in cycloaddition.
The reaction of azido compounds and acid produces hydragoic acid. The reac-
tions of hydragoic acid and other ions generate explosive chemical compounds with
high risk. The reaction of azido chemicals with base is a saponi
cation reaction.
This reaction decomposes the chemicals but it is not dangerous.
(2) Stabilities of azido compounds
The thermal decompositions of azido compounds are of two types
ionic and
covalent bonds. Most of organic azido compounds are covalent azido compounds.
The electromagnetivity of
—
-
N
3
group strengthens the C
-
N bond. So the bond
lengths of two N
-
N bonds in
-
MN
3
groups are different. The bond lengths of
triazido triazinane trione are
1.26
1.18
. The decomposition of chemicals is as in
N
N
N
the below equation.
R
N
3
RN + N
2
In ionic inorganic azido compounds [
8
], the lengths of N
-
N bonds are the same
(the polarization of azido group is not in consideration). N
N bonds are not broken
-
in the decomposition, which follows below equations.
MN
3
M+N
3
(I)
N
3
N
3
+ e
(II)
2N
3
!
3N
2
(III)
Most azido compounds explode in their decomposition. But thermochemistry,
photochemistry, and discharge methods can slow down the decomposition reaction.
The products of explosive decomposition are the corresponding simple substances.
Decomposition heat of one compound equals its standard formation heat.
Some decomposition reactions generate nitrides.
3LiN
3
!
Li
3
N+4N
2
"
