Org. Synth. 1951, 31, 19
DOI: 10.15227/orgsyn.031.0019
o-CHLOROPHENYLCYANAMIDE
[Carbanilonitrile, o-chloro-]
Submitted by Frederick Kurzer
1
Checked by Cliff S. Hamilton and David B. Capps.
1. Procedure
To a suspension of
37.4 g. (0.2 mole) of o-chlorophenylthiourea (p. 180) in 300 ml. of water at 100°, contained in a
3-l. beaker, is added a boiling solution of
132 g. (2 moles) of 85% potassium hydroxide in 300 ml. of water. The resulting solution is immediately treated with a hot saturated solution of
83.5 g. (0.22 mole) of lead acetate trihydrate, added as rapidly as possible and with good stirring
(Note 1). The reaction mixture, from which large quantities of
lead sulfide separate instantly, is boiled for 6 minutes and cooled to 0°, and the
lead sulfide is filtered with suction by means of a
large Büchner funnel (Note 2). The colorless filtrate is acidified at 0–5°
(Note 3) by the slow addition with stirring of
120–140 ml. of glacial acetic acid. The white crystalline precipitate of nearly pure
o-chlorophenylcyanamide which separates is collected by filtration on a
suction filter and is washed with six 150-ml. portions of ice water. The crystalline mass of white plates is filtered, drained, and dried
(Note 4). The yield of product, melting at
100–104°, is
26–28 g. (
85–92%).
Recrystallization from benzene-light petroleum ether (8 ml. and 4 ml. respectively per gram of the dried precipitated material) gives lustrous needles of o-chlorophenylcyanamide, m.p. 105–106° (60–70% recovery) (Note 5). The above method is generally applicable and affords an excellent route to arylcyanamides (Note 6).
2. Notes
1.
The exothermic reaction may cause the contents of the beaker to froth vigorously if the
lead acetate solution is added too quickly. The reaction is readily controlled by adding the liquid in a rapid, thin stream with good stirring.
2.
The use of a hardened filter paper or two thicknesses of ordinary filter paper is recommended. The black filter cake of
lead sulfide may be extracted once again with
100 ml. of boiling 4% potassium hydroxide solution, and the extracts combined with the main filtrate.
3.
The temperature of the solution is kept below 5° by the addition of suitable quantities of clean ice.
4.
The product is sufficiently pure for use in further syntheses.
5.
In
benzene solution or in the solid state,
o-chlorophenylcyanamide does not polymerize on storage for several months at 20–30°.
6.
The desulfurization of arylthioureas can be used generally for preparing arylcyanamides in excellent yields. The submitter reports that
α-naphthylcyanamide, melting at
124–128°, can be prepared in yields of
77–90% by this method.
3. Discussion
o-Chlorophenylcyanamide has been prepared by the action of
lead acetate on
o-chlorophenylthiourea.
2 The method is based on the analogous preparation of
phenylcyanamide.
3
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
α-naphthylcyanamide
acetic acid (64-19-7)
Benzene (71-43-2)
lead sulfide
potassium hydroxide (1310-58-3)
lead acetate
phenylcyanamide
o-Chlorophenylthiourea (5344-82-1)
o-Chlorophenylcyanamide,
Carbanilonitrile, o-chloro- (45765-25-1)
lead acetate trihydrate
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