One hundred nine grams (1 mole) of p-aminophenol (Note
1) is dissolved in a mixture of 500 g. of ice, 500 cc. of water, and
65 cc. (120 g., 1.2 moles) of concentrated sulfuric acid (sp. gr. 1.84). To this solution, kept in a freezing mixture at 0°, is added, during the course of an hour with constant mechanical stirring, a solution of
72 g. (1 mole) of 95 per cent sodium nitrite in 150 cc. of water. The stirring is continued twenty minutes longer, and then
20 cc. (37 g., 0.37 mole) of concentrated sulfuric acid is added.
This solution is poured into an ice-cold solution of
200 g. (1.2 moles) of potassium iodide in 200 cc. of water. After a few minutes,
1 g. of copper bronze (Note
2) is added, with continued stirring, and the solution is warmed slowly on the
water bath. The temperature is kept at 75–80° until the evolution of
nitrogen ceases; during this process the
iodophenol separates as a heavy dark oil. After cooling to room temperature the reaction mixture is extracted three times with
165-cc. portions of chloroform and the combined extracts are washed with dilute thiosulfate solution. The solvent is removed on the water bath and the residue distilled under reduced pressure, the
p-iodophenol coming over at
138–140°/5 mm. One crystallization from about
2 l. of ligroin (b.p.
90–110°) gives a colorless product melting sharply at
94°. The yield of recrystallized product is
153–159 g. (
69–72 per cent of the theoretical amount).