Organic Syntheses, CV 1, 165
Submitted by G. Malcolm Dyson
Checked by Frank C. Whitmore and P. L. Cramer.
1. Procedure
In a
5-l. crock or battery jar, provided with a
powerful mechanical stirrer, are placed 3.5 l. of water and
249 g. (165 cc., 2.16 moles) of thiophosgene (p. 506) (Note
1). To the vigorously stirred (Note
2) mixture is added slowly
255 g. (2 moles) of p-chloroaniline during about one-half hour. The stirring is continued for about an additional one-half hour. The dark brown oil is separated, washed with
50 cc. of 10 per cent hydrochloric acid, and placed in a flask for steam distillation.
The flask is immersed in an
oil bath heated to 120° and dry steam is then passed through the reaction mixture. The first few cubic centimeters of distillate contain the excess of
thiophosgene and are discarded. The
isothiocyanate passes over with the water as an oil that solidifies on cooling. The steam distillation requires about four hours. The crude material is crystallized from two parts of
ethyl alcohol at 50°, from which it separates as white needles melting at
44–45°. The yield is
245–275 g. (
72–81 per cent of the theoretical amount) (Note
3).
2. Notes
1. Because of the objectionable properties of
thiophosgene, care should be exercised in its use.
2. The stirring at the start must be very vigorous or the yield is decreased.
3. The method is general for alkyl- and halogen-substituted aromatic amines. An alternative procedure which gives lower yields but avoids the use of
thiophosgene will be found on
p. 447.
3. Discussion
This preparation is referenced from:
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