M-Bromonitrobenzene

Pour the resulting dark reddish-brown liquid into 500 ml. of water to which 17 ml. of saturated sodium bisulphite solution has been added (the latter to remove the excess of bromine). Steam distil the resulting mixture (Fig. II, 41,1) , collect the first portion of the distillate, which contains a little unchanged nitrobenzene, separately. Collect about 4 litres of distillate. Filter the yellow crystalline solid at the pump, and press well to remove the adhering liquid. The resulting crude m-bromonitrobenzene, m.p. 51-52°, weighs 110 g. If required pure, distil under reduced pressure (Fig. II, 19, 1) and collect the fraction of b.p. 117-118°/9 mm. it then melts at 56° and the recovery is about 85 per cent. 

Intermediates benzene to nitrobenzene to m bromonitrobenzene to m bromoanihne to m bromophenol Reagents HNO3 H2SO4 Br2 FeBr3 Fe HCl then HO NaN02 H2SO4 H2O then heat in H2O... 

A yield of 84 per cent of u-nitrodiphenyl ether boiling at i83-i85°/8 mm. is obtained when o-nitrochloro benzene is used. For the preparation of j-nitro diphenyl ether, the method of Ullmann and Sponagel, using m-bromonitrobenzene, seems to be the best, since m-chloro nitrobenzene gives large amounts of tarry matter. 

The reaction product, which is a dark reddish-brown liquid, is poured or siphoned (Note 5) into 1.5 1. of water to which 50 cc. of a saturated solution of sodium bisulfite has been added (Note 6). The mixture is distilled with steam (Org. Syn. 2, 80) and the first portion of the distillate is collected separately to remove a small amount of unchanged nitrobenzene. It is necessary to collect about 12 1. of distillate in order to obtain all of the m-bromonitrobenzene. The yellow crystalline solid is filtered with suction and pressed well on the funnel to remove water and traces of nitrobenzene. The yield of crude product varies from 270-340 g. (60-75 Per cent °f the theoretical amount). It melts at 51.5-520 and boils at 117-118 79 mm. This product is satisfactory for most purposes. If a purer material is desired, the crude /w-bromonitrobenzene may be distilled under reduced pressure. The recovery on purification is about 85 per cent. Briihl recorded the b.p. as 1380/18 mm. and the m.p. as 56° for pure wz-bromonitrobenzene.1... 

Write chemical equations showing how you could prepare m-bromonitrobenzene as the principal organic product, starting with benzene and using any necessary organic or inorganic reagents. How could you prepare p-bromonitrobenzene ... 

The product that is obtained when benzene is subjected to bromination and nitration depends on the order in which the reactions are carried out. Anitro group is meta-directing, and so if it is introduced prior to the bromination step, m-bromonitrobenzene is obtained. 

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