CORRESPONDENCE A NOTE ON THE PREPARATION OF m-DINITROBENZENE To the Editor DEARSIR: Meta-dinitrobenzene is a preparation which is included in almost every course of organic preparations which a junior student is expected to go through. All the hooks which we came across recommend the use of fuming nitric a d d for the preparation of meta-dinitrobenzene from nitrobenzene. This is likely to create an impression that without the use of fuming nitric acid (sp. gr. 1.52), the second nitro group cannot be introduced. Once when we suddenly found that we were short of fuming nitric add, we used ordinary concentrated nitric a d d (sp. gr. 1.42) to see whether it could be substituted if the amount of sulfuric acid was increased. We found that fuming nitric acid was not at all indispensable. The following table gives the proportions recommended in the literature and those tried by us, with the yields given in each case. N h b m m (9.) Gattermam "Die Praxis des Organischen Chemikers" 10 Sudburough and James "Practical Organic Chemistly" 10 Our experiments 10 10 10
Theoretical
Nihic acid
Sulfuric acid
Yicld
(9.)
(9.)
(9.)
15 (fuming)
25 (conc.)
10-12
17.5 (fuming)
20 (conc.)
12
15 (sp. gr. 1.41) 25 (sp. gr. 1.82) 15 (sp. gr. 1.41) 30 (sp. gr. 1.82) 15 (so. er. 1.41) 35 (so. er. 1.82)
4 9 11.5
10 15 (SP.gr. i.41j 50 (SP.gr. 1.82j 10
12 13.6
~.-
..
It would he interesting to note that fuming nitric acid is eight per cent. dearer than ordinary concentrated nitric atid (sp. gr. 1.42) and that concentrated sulfuric add is seventy per cent. cheaper than fuming nitric add. S. v. S ~ A H D. G. P I S B A W ~
[In the fourth line from the bottom, "eight" should be "eighty". Correction published in July, 1937, issue, p. 323.]
