urbaf2

NITRATION AND NITRATING AGENTS 49

Since industrial nitration occurs, in most cases, in two-phase system a number

of workers have investigated the kinetics in both phases: organic and acid. Hethe-

rington and Masson [84], McKinley and R. R. White [I18], Barduhn and Kobe

[119] all reported that nitration of aromatic hydrocarbons takes place only in the

acid phase. However, other workers (W. K. Lewis and Suen [120]) have shown,

when nitrating benzene, that the reaction rate in the organic phase is an

appreciable fraction (10-15%) of that in the acid phase.

As mentioned already (p. 40) it appears that nitration takes place mainly (but

not exclusively) in the acid phase.

Taking into consideration that the rate of reaction in the organic phase is

negligible compared with that in the acid phase, the following definition of the

rate of nitration, R, of toluene in the unit volume of acid phase can be given

moles of MNT produced

R=

hr x litre of acid phase

Brennecke and Kobe [117] reported that the rate of nitration of toluene appears

to be proportional to the mole fraction of toluene in the effluent organic phase

XT (for acids containing not more than 30 mole % sulphuric and 15 mole %

nitric acid). This suggested that the ratio R:XT is the rate that would be obtained

if the organic phase were pure toluene. Kobe came to the conclusion that the

mechanism of nitration through the nitronium ion controls the rate of reaction

in acids containing more than 30 mole % of sulphuric acid.

The fact that most industrial nitrations take place in a two-phase system neces-

sitated investigations into the influence of mixing on the rate of reaction.

A few authors, e.g. Kobe and his co-workers [117, 119], Orlova [123] have

found that the rate of nitration greatly depends on the intensity of agitation of

a reacting mixture. This is discussed in a more detailed way in the chapter de-

voted to the practical principles of nitration, i.e. the technology of the process

and apparatus for nitration (pp. 152, 266, 288, 314).

LITERATURE

1. A, F. HOLLEMAN, Die direkte Einfiihrung von Substituenten, Leipzig, 1910.


2. J. MENKE, Rec. trav. chim. 44, 141 (1925).


3. E. SCHMIDT, Ber. 52, 400 (1919).


4. N. KORNBLUM, H. 0. LARSON, R. H. BLACKWOOD, D. D. MOOBERRY, E. P. OLIVETO and
   G. E. GRAHAM, J. Am. Chem. Sot. 78, 1497 (1956).
   4a. N. KORNBLUM, J. Org. Chem. 22, 45.5 (1957).


5. L. R. MAXWELL and V. M. MOSLEY, J. Chem. Phys. 8, 738 (1940).


6. J. CHÉDIN, J. phys. radium 10, 445 (1939;.


7. R. M. BADGER and S. H. BAUER, J. Chem. Phys. 4, 711 (1936); 5, 839 (1937).


8. R. DALMON, Compt. rend. 207, 473 (1938); 211, 782 (1941).


9. R. DALMON and R. FREYMANN, Mém. Serv. Chim. l’État 31, 58 (1944).


10. V. LUZZATI, Mém. Serv. Chim. l'État 35, 7 (1950); Acta Cryst. 4, 120 (1951).