A.
2-Bromo-4-nitrotoluene. In a
200-ml. three-necked, round-bottomed flask provided with an
efficient reflux condenser bearing a suitable
trap for absorbing
hydrogen bromide, a
100-ml. separatory funnel, and a
ball-joint or mercury-sealed mechanical stirrer are placed
68.5 g. (0.5 mole) of p-nitrotoluene (Note
1) and
1.0 g. of iron powder. The mixture is heated to 75–80° by means of a
water bath, vigorous stirring is begun, and
30.5 ml. (94.8 g., 0.59 mole) of bromine is added over the course of 30 minutes. After the addition of
bromine is complete, the reaction mixture is maintained at 75–80° with continuation of stirring for an additional 1.5 hours.
The reaction mixture is poured with vigorous stirring into
750 ml. of ice-cold 10% sodium hydroxide solution, the solid is allowed to settle, and the supernatant liquid is decanted. To the residue is added
250 ml. of glacial acetic acid, and the mixture is heated until the solid is completely melted. The two liquid phases are thoroughly mixed by stirring, the mixture is cooled to 5° in an
ice bath, and the supernatant liquid is decanted. The product is then heated with
500 ml. of 10% acetic acid until molten, stirred thoroughly, and cooled to room temperature. The aqueous liquor is decanted, and the cycle is repeated with
500 ml. of 1% sodium hydroxide solution (Note
2). The solid
2-bromo-4-nitrotoluene is collected on a
Büchner funnel and thoroughly washed with water. The moist product may be used directly in the next stage of the synthesis. It can be dried to yield
93–97 g. (
86–90%) of light-brown material melting at
75–76°.