Organic Syntheses, Coll. Vol. 3, p.668 (1955); Vol. 25, p.80 (1945).
A mixture of 250 ml. (2.44 moles) of nitrobenzene (Note 1)
and (Note 2)
and a solution of 150 g. of ammonium chloride
in 5 l. of water in a 5-gal. crock (Note 3)
is stirred vigorously (Note 4)
, and 372 g. (5.15 moles) of zinc dust (90% zinc)
is added in small portions over a period of 5 minutes. About 5 minutes after the addition of the zinc
, the main reaction occurs and the temperature rises. When the temperature reaches about 65°, enough ice is added to the stirred mixture to bring the temperature down to 50–55° (Note 5)
. Twenty minutes after the addition of zinc
was started, the solution is filtered through a 24-cm. Büchner funnel
and the zinc oxide
residues are washed with 3 l. of boiling water. The filtrate and washings are combined in a 6-gal. crock (Note 6)
and cooled immediately (Note 7)
by the addition of enough ice to bring the temperature to 0° to −2° and leave at least 1 kg. of ice unmelted.
To this cold solution or suspension of β-phenylhydroxylamine
, a cold solution of sulfuric acid (750 ml. of concentrated acid and sufficient ice to bring the temperature down to −5°)
is added with stirring. An ice-cold solution of 170 g. of sodium dichromate dihydrate
in 500–750 ml. of water is added as rapidly as it can be poured into the mixture, which is stirred or swirled (Note 8)
. After 2 to 3 minutes, the straw-colored precipitate of nitrosobenzene
is collected on a Büchner funnel and washed with 1 l. of water (Note 9)
The crude nitrosobenzene
is steam-distilled (Note 10)
, and the distillate is collected in a receiver
cooled by ice (Note 11)
. The nitrosobenzene
is finely ground in a mortar
, transferred to a Büchner funnel, and washed with water until the washings are no longer brown. After it has been sucked as dry as possible on the filter the nitrosobenzene
is pressed between layers of filter paper
(or other porous paper). One or two changes of paper may be necessary. The yield of nitrosobenzene
melting at 64–67°
is 128–138 g.
%) (Note 12)
and (Note 13)
. If a purer product is desired, the crude nitrosobenzene
can be recrystallized from a small amount of ethanol
with good cooling, and the product dried over calcium chloride
at atmospheric pressure.
The checkers used a 12-l. round-bottomed flask
Vigorous stirring is necessary in order to prevent the zinc
dust from caking on the bottom of the crock. The submitters employed two mechanically driven stirrers in order to keep the zinc
dust in suspension. The checkers used a single paddle stirrer
At higher temperatures secondary reactions take place.
The checkers used a 22-l. round-bottomed flask
decomposes on standing, the filtrate should be cooled as soon as the filtration is completed, and the oxidation to nitrosobenzene
should be carried out immediately. An excess of ice should be present since the oxidation reaction is exothermic and the temperature of the solution should still be near 0° after the oxidation. At higher temperatures oxidation products other than nitrosobenzene
It is important to add the dichromate solution rapidly in order to obtain a good yield of easily filterable product. In a run in which the dichromate solution was added over a period of 25 minutes, only a 10%
yield of nitrosobenzene
This product is stable for about a week if kept at 0°.
Connections should be of glass since cork and rubber are attacked readily. Since nitrosobenzene
decomposes at the elevated temperature, it should be steam-distilled as rapidly as possible. If several runs are made, not more than four or five should be combined for distillation. A Hopkins still head is effective for preventing contamination.
condenses to a green liquid which solidifies to a white solid. Care should be taken that the solid does not clog the condenser. Distillation is stopped when yellow oily material appears in the condenser.
Cooling of the receiver is necessary because the nitrosobenzene
has a very high vapor pressure at room temperature.
Yields as high as 65–70%
have been obtained in smaller runs.
can be kept at room temperature in a closed container
for 1–2 days. Over longer periods it should be stored at 0°.
can be prepared by the oxidation of aniline
with permonosulfuric acid1
or peracetic acid2
and by the oxidation of β-phenylhydroxylamine
which is prepared by the reduction of nitrobenzene
. Purification by sublimation has been recommended.4
This preparation is referenced from:
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