Environmental Engineering Reference
In-Depth Information
Table 4.1 Infrared
absorption peaks of nitro
groups [
5
]
as
/cm
−
1
s
/cm
−
1
/cm
−
1
Nitro compounds
˃
˃
ʔ˃
Primary nitroalkane
1,550
-
1,567
1,368
-
1,379
190
Secondary nitroalkane
1,545
-
1,565
1,360
-
1,383
180
Tertary nitroalkane
1,530
-
1,545
1,342
-
1,358
190
2,2-dinitropropane
1,575
-
1,587
1,327
-
1,337
250
Dinitromethane
1,538
-
1,550
1,375
-
1,389
150
-
200
1,1,1-trinitromethane
1,603
1,298
-
1,303
300
Nitrobenzene
1,510
-
1,540
1,345
200
Note
ʔ˃
is the wavenumber of the two vibrations, therefore, the number of
nitro groups can be determined according to
ʔ˃
4.2.2 Chemical Properties of Liquid Nitro Compounds
(1) Chemical Stability
Nitroalkanes have acidic isomers and tautomerism, in which primary and sec-
ondary nitroalkane are acidic because their
α
-hydrogen atoms are in
fl
uenced by the
nitro group, and can be con
gured tautomerically into acidic structure.
K
i
RCH
2
NO
2
RCHNO
2
H
K
a
K
aci
H
+
RCHNO
2
+
With the increase of the number of nitro groups in nitomethane, pKa is 10.2, 3.6
and 0.2, respectively [
1
]. The stability of nitroalkane salt is very poor, and can be
automatically decomposes with heat or long-term storage, and, especially, the dry
explosive nitro compounds salts are very sensitive to heat, impact, friction, static
electricity and
flame; dry nitromethane salt may explode when it is getting wet, and
the sensitivity of salt of nitro group on aromatic ring is many times higher than that
of the corresponding nitro compounds;
fl
-
hydrogen atom, thus, the above-mentioned tautomeric isomerization reaction could
not occur, and they could not react with bases to generate salts.
(2) Reaction with Acid
When equal amount of concentrated mineral acid and primary nitroalkane react,
a carboxylic acid and a hydroxylamine salt are generated, generally with yield of up
to 85
tert-nitroalkanes do not have any
α
90 %. When sulfuric acid reacts with nitromethane [
6
], products are CO and
hydroxylamine sulfate. The mixture from the reaction between anhydride sulfuric
acid and a primary nitroalkane at 60
-
C was poured into ice-water and then
treated with Ca(OH)
2
, an intermediate, hydroxamic acid
(
R-C-NHOH
°
O
)
between car-
boxylic acid and hydroxylamine can be produced with a yield of 55 %. Salt from
