NITRO DERIVATIVES OF HIGHER BENZENE HOMOLOGUES 409xylene a temperature of 35-40°C is maintained. Then it is gradually raised to
100°C, where it is maintained for 14 hr.
After cooling (while stirring) the dinitroxylene, which is partly crystalline and
partly oily, is separated from the spent acid by centrifugation. The melting point
of the product ranges from 37° to 61.5°C.
From 100 parts by weight of xylene 163.8 parts by weight of dinitroxylene are
obtained, the yield being 94% of theory.
The composition of the spent acid is:
HNO 3 1.7%
H 2 SO 4 74.3%
H 2 O 24.0%
The wet product is separated into two fractions - liquid (oily) and solid. Usually
20% of liquid and 80% of solid dinitro-m-xylene is obtained.
For the second stage of the process, i.e. trinitration, the DNX liquid or solid
obtained is charged into the nitrator and acid of a composition:
HNO 3 18%
H 2 SO 4 60%
H 2 O 2%
is added.
For 1 part of DNX 3.2 parts of the nitrating mixture are run in, thus the excess
of HNO 3 is 80% of the calculated amount.
Temperatures during the operation are maintained as follows: 50-55°C during
addition of the acid, then 110°C for an hour, and finally 120°C for two hours.
When nitration is completed, TNX is separated from the spent acid on a vacuumfilter, after cooling to 20°C.
The spent acid from the process has the following composition:
HNO 3 6%
H 2 SO 4 86%
H 2 O 8%
From 100 parts of DNX 105 parts of TNX are obtained, which makes 86%
of the theoretical yield.
From liquid DNX solid grade II TNX (m. p. 164°C) and liquid TNX are both
obtained.
From solid DNX grade I crystalline TNX (m. p. 177°C) is obtained.
100 kg of m- xylene yield the following quantities of TNX:
147-154 kg of the grade I product
25.6 kg of the grade II product
1.0 kg of the liquid product.
Nitration via MNX. The process worked out by Filippov [8a] consists of twostages: mononitration followed by trinitration.
For one part of m- xylene, 2.5 parts of nitrating mixture of the composition:
HNO 3 25%
H 2 SO 4 59%
H 2 O 16%