Organic Syntheses, Coll. Vol. 3, p.711 (1955); Vol. 25, p.86 (1945).
Fifty-four grams (0.39 mole) of p-aminobenzoic acid
is dissolved in 390 ml. of warm glacial acetic acid
in a 1-l. Erlenmeyer flask
. The solution is cooled to room temperature, 42 g. (0.39 mole) of nitrosobenzene (p. 668)
is added, and the mixture is shaken until the nitrosobenzene
dissolves. The flask is stoppered, and the solution is allowed to stand for 12 hours at room temperature. The product begins to crystallize after about 15 minutes.
The p-phenylazobenzoic acid
is collected on a Büchner funnel (Note 1)
and washed with acetic acid
and with water. The yield of air-dried acid melting at 245–247°
cor. is 62 g.
). By recrystallization from 95% ethanol (60 ml. per g.)
the acid is obtained as orange-gold plates which melt at 248.5–249.5°
cor.; the yield is 54 g.
The solution is not cooled below room temperature before filtering; cooling below 20° brings down impurities.
The method employed here is essentially the one described by Angeli and Valori.1
This preparation is referenced from:
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