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NITRO DERIVATIVES OF TOLUENE 273

The results from nitration at four different temperatures are given in Table 49.

TABLE 49

Temperature Yield of mixed % of m- nitrotoluene

°C nitrotoluenes in mixed nitrotoluene

0 100 2.08

30 92 3.44

45 84 4.18

60 4.70

Noelting and Forel [11] found that the content of p- nitrotoluene increased

gradually with increase in the HNO 3 content of the nitrating acid. Thus, when

nitrating toluene with a mixture of nitric and sulphuric acids, the authors obtained

60% of the p- isomer but if nitric acid alone was used, 66% of p- nitrotoluene was

obtained.
The effect of temperature and of the composition of the nitrating mixture on

the quantity of m- nitrotoluene formed has been the subject of numerous studies.

The results are shown in Table 50.

The order of introducing the reagents may also affect the composition of the

nitration product. For example, if the toluene is added to the acid, then the first

portions of toluene come into contact with a large excess of acid, and the nitration

process may proceed beyond mononitration resulting in a mixture of di- and mono-

nitrotoluene. If the amount of HNO 3 used has been calculated accurately, the

last portions of toluene may be left unnitrated and the resultant product may

not be uniform. If, on the contrary, the acid is added to the toluene, an excess

of acid cannot occur, since each portion added reacts with the toluene very quickly.

TABLE 50

INFLUENCE OF TEMPERATURE AND COMPOSITION OF NITRATING MIXTURES

ON m- NITROTOLUENE FORMATION

Nitration m- Nitrotoluene content, %

temperature

°C (1) (2a) (2b) (2c) (3)

-30 3.5 - - - -

0 3.9 2.5 4.5 3.3 3.7

(^20) - 4.3 4.5 3.9 -
30 4.4 - - - 4.4
(^40) / - - 4.2 -- -
(^50) 4.3
60 5.1 - - - -
(1) Hollemart, Vermeulen, de Mooy [12].
(2) Gibson. Duckham, Fairbairn [13]: (a) -nitration with 94% nitric acid; (b) -
(4)
2.97
5.68

• 4.39


• 
  


• 
  

  4.90

  
  

nitration with a mixture:

HNO 3 -23.8%. H 2 SO 4 -58.7%. H 2 O-17.5%; (c)-nitration with a mixture: HNO 3 -13.7%. H 2 SO 4 -64.4%. H 2 O-

-21.9%.

(3) Ingold. Lapwotth, Rothstein and Ward [14] -nitration in acetic anhydride and nitromethane.

(4) W. W. Jones and Ruse1 [9] -nitration with a mixture: HNO 3 -5.35%, HNO 2 -1.75%. H 2 SO 4 -71.4%.

H 2 O-21.5%.