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286 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

The crude dinitrotoluene consists (according to de Beule) of the following iso-

mers :
2.4-dinitrotoluene 76.1%
2,6-dinitrotoluene 19.8%
3,4-dinitrotoluene 2.25%
2,3-dinitrotoluene 1.23%
2,5-dinitrotoluene 0.54%
3,5-dinitrotoluene 0.08%

Recently Kobe, Skinner and Prindle [32] reported their extensive studies on

the nitration of o- and p- nitrotoluenes to dinitrotoluene. They concluded that

the most favourable parameters of the nitration of o- and p- nitrotoluenes differed

somewhat from each other. Thus the concentration of mixtures for nitrating o- nitro-

toluene might vary within a wider range, especially with regard to the quantity

of sulphuric acid. Also, lower temperatures may be applied for the nitration of

o- nitrotoluene.

According to these authors, the following conditions are the most favourable

in the nitration of 200 g of nitrotoluenes:

o- Nitrotoluene p- Nitrotoluene

Nitric acid weight theoretical theoretical

Sulphuric acid weight 250-350 g 350 g

Sulphuric acid concentration 90% 90%

Temperature 50°C 65°C

Reaction time 15-20 min 15-20 min.

Yield 100% 98%

Figures 59, 60 and 61 show the influence of temperature and concentration

of sulphuric acid on the yield of dinitrotoluene using o- and p- nitrotoluene as

starting materials.

Gorst and Trufanova [32a] stated that the nitration of p- nitrotoluene pro-

ceeds with a noticeable rate at 70°C when the nitrating mixture has the factor

Φ = 72%. Increase of Φ to 79.84% increases the rate of the reaction five times

(Table 59 and Fig. 62).

TABLE 59

Φ,% 71.83 74.07 75.92

mole

Rate,- x 10 -2 16.3 42.9 60.6

1. min

Quantity of nitrated mono-

nitrotoluenes,% 17.8 46.5 65.1

77.77 79.84

74.4 85.0

78.7 88.8

Increased rate of stirring also produces an increase in the rate of nitration.

Orlova [32a] gives a diagram (Fig. 63) related to the nitration of p- nitrotoluene

with nitrating mixture containing 4% HNO 3 , 74% H 2 SO 4 and 23% H 2 O at 70°C.