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(Michael S) #1
NITRO DERIVATIVES OF PHENOL 485

The hydrolysis process is effected in a wrought iron reactor of 4 m^3 capacity,


equipped with a cooling jacket, a heating coil and a stirrer. The reactor is charged
with water heated to 70°C then a 42% solution of NaOH is run in from
a measuring tank in such a quantity as to obtain 2130 1. of a 7% NaOH
solution (5% in excess of the calculated quantity). Then 360 kg of molten chloro-
dinitrobenzene at a temperature of 70-75°C is added over a period of 10 min.
The temperature rises to 100°C. When the vigorous stage of the reaction has
subsided the mixture is heated to 100-110°C for 1 hr.
Towards the end of this operation a sample should be taken and diluted with
water to test whether hydrolysis is complete. A completely hydrolysed product
will go into solution. Otherwise chlorodinitrobenzene will collect as an oil.
According to Lebedev, the hydrolysis process requires 2 hr 20 min, including
the following schedule of operations:
charging with water 15 min
charging with sodium hydroxide solution 10
analysis of the solution 10
introducing chlorodinitrobenzene 10
heating at 100-110°C 60
analysis 10
pumping out the reactor contents^15
blowing out the pipes^10
Total 2hr20min


As a result of the hydrolysis process a sodium dinitrophenate solution is formed.
To obtain’dinitrophenol this solution is transferred to a wooden vat containing
30% sulphuric acid in a quantity exceeding the calculated amount by 5%. Spent
acid from the nitration, diluted with water to the required concentration, may
be used.
After testing the suspension for complete acidification (with Congo red test
paper), it is transferred by compressed air, while still hot (70°C), to a cloth-lined
vacuum filter. The dinitrophenol is washed on the filter 3-4 times with water until
the acid content in the washings is reduced to 0.01%. Then it is centrifuged in copper
centrifuges to a moisture content of 12-15%.
According to Lebedev, the time required for the conversion of dinitrophenate
to dinitrophenol is 60 min individual operations requiring:

charging the reactor with acid 10 min
introducing the dinitrophenate 15
stirring 15
analysis 10
draining off on the filter 10
Total 60 min

The product is then dried to reduce the moisture content to 1-2%.
From 100 kg of chlorodinitrobenzene roughly 82 kg of dinitrophenol is obtained,
the yield being 91% of the theoretical.
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