Organic Syntheses, Coll. Vol. 1, p.136 (1941); Vol. 5, p.21 (1925).
When the hydrobromic acid-cuprous bromide
solution is ready for use, the diazonium solution is prepared. A solution of 107 g. (1 mole) of p-toluidine
and 196 g. (107 cc., 1.9 moles) of concentrated sulfuric acid
(sp. gr. 1.84) in 1 l. of water is cooled below 20° and diazotized with a solution of 70 g. (1 mole) of sodium nitrite
in 125 cc. of water. This requires about twenty to thirty minutes when the temperature is maintained between 15° and 20° by means of an ice bath
A 5-l. round-bottomed flask
containing the hydrobromic acid-cuprous bromide
solution, is arranged for steam distillation. After the copper solution is heated to boiling, the diazonium solution is gradually added from a separatory funnel
and a vigorous current of steam is passed through the reaction mixture at the same time. This procedure requires about two hours.
The aqueous distillate is made alkaline with sodium hydroxide
solution and the p-bromotoluene
is separated from the water layer (Note 2)
. The crude product weighs 131–137 g.
For purification the crude product is washed once with concentrated sulfuric acid (Note 3)
and then with water. It is dried over a little calcium chloride
, filtered, and distilled. The yield of pure product amounts to 120–126 g.
per cent of the theoretical amount) boiling at 183–185°
and melting at 25–26°
If the color of the solution has not been discharged after heating for three to four hours, a few grams of sodium sulfite
may be added to complete the reduction.
A small amount of ether
may be used to aid in the separation if it is needed.
This preparation is referenced from:
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