THE PREPARATION OF m-DINITROBENZENE To the Editor DEARSIR: In the January (1937) issue of THISJOURNAL (P. 33) we published a note on the preparation of m-dinitroTABLE1 Nilro- So- Sulben- dium j u r i ~ No. zene n+r?te ac@ Yi+ 2 3 4 -
(E.1
(9.)
10 -~ 10 10
7 10 14 20
(8.) 16 37
42 46 48
32
7 8 9
." 11 ~n
12 13 14 15 16 17 18
10 10 10 i-" n 10 10 10 10 10 10 10 10
7 8 8 rn -" 14 20 7 10 14 20 14 10
41 37 42 m 46 48 41 42
$6
48 46 42
(9.) 4,3
10.8 12.3 12.3 12.15
9,8 11.2 10.8 11.4
Remarks Refluxing on bath at 140'150°C., after completion of the initial reaction which starts at about 8 0 ~ or earlier. pure sodium nitrate was used in all these experiments. As above, but instead of ail bath, water bath wasused.
-1-1. *A
12.1 12.2 11.2 Experiments 13-18 were 11.5 caniedoutonwater 11.8 bath, using commercia1 scdium nitrate. 11.7 11.47 (Average of four junior 11.36) students)
benzene and showed that in this preparation fuming nitric acid was not indispensable; on the other hand by
From the results, it can be seen that the proportions used in experiments 2 , 3, 4, 7, 9, 10, 11, 14, and 15are very convenient. The average yields obtained in these cases vary between 10 and 12 grams. The same yield is obtained by using fuming nitric acid. The technic of the method is as follows. Nitrobenzene and sodium nitrate are taken in a round bottom flask. Concentrated sulfuric acid is gradually added and the mixture is shaken from time to time. (Sometimes the reaction st&s even at this stage if the shaking is sufficiently Yi~orous.) The flask fitted with an air-condenser is heated on a water bath. At about 80°C. the reaction ~starts , when the flask with the condenser is removed from the water bath and shaken. The reaction bectins to be vigorous and after about ten minutes slowly subsides. (It is better to heat the mixture a t this stage slowly on wire-gauze and ensure the complete liberation of nitric acid. This precaution is absolutely necessary when commercial sodium nitrate is used.) The mixture is then heated on water bath without any condenser until a test portion of the same, poured in water, separates out as a solid cake. In all, the reaction takes one hour. While i t is still hot the whole mass is poured into a large quantity of water. Dinitrobenzene, which solidifies, is filtered off, washed with cold water, and dried on a porous plate, the final drying being done over sulfuric acid in a desiccator. If one tries to compare the cost of materials as required for ten grams of nitrobenzene, by the different
-
Futning Ordinary
Nilric Add
Nilric Acid
Sodium Nilrate Pure
Sodium Nitrate Commer- Suljuri~ cia1 Acid
TOW Cost
Yield
Gattermam, "Die Praxis des Organischen Chemikers" Sudburough and James, "Practical Organic Chemistry" Our best experiment, described on page 33 of the January, 1937, issue of the JOURNAL OF CKBMIcnr. EDUCATION Average of experiments 7.9. 10, and 11, this paper Average of experiments 13, 14, and 15 Experiment 17 Experiment 18
increasing the quantity of sulfuric acid, ordinary nitric acid (SP, GR. 1.4) could also bring about the further nitration of nitrobenzene to m-dinitrohenzene. It was also shown that the total cost could be reduced by this method. We tried to develop this method and stumbled upon the idea of eliminating nitric acid altogether. We made use of a mixture of sodium nitrate and sulfuric acid. The results are given in Table 1.
methods, the results given in Table 2 may be obtained. The figures in Table 2 indicate units representing averageprices.
S. V. SHAH D. G. PISHAW~~AR OF
RAJARAM COLLEGE K O L X A PINDIA ~,
