Org. Synth. 1945, 25, 87
DOI: 10.15227/orgsyn.025.0087
p-PHENYLAZOBENZOYL CHLORIDE
[Benzoyl chloride, p-phenylazo-]
Submitted by George H. Coleman, Gust Nichols, Chester M. McCloskey, and Harry D. Anspon.
Checked by W. E. Bachmann and N. C. Deno.
1. Procedure
Fifty grams (0.22 mole) of recrystallized p-phenylazobenzoic acid (p. 711) (Note 1) and
50 g. (0.47 mole) of anhydrous sodium carbonate (Note 2) are placed in a
1-l. flask and thoroughly mixed by shaking. To this mixture is added
250 ml. (3.5 moles) of thionyl chloride (Note 3); a
reflux condenser with a drying tube is fitted to the flask, and the mixture is refluxed for 1.5 hours
(Note 4). A condenser is set for distillation, and as much as possible of the
thionyl chloride is distilled on a
steam bath (Note 5).
The acid chloride is dissolved by refluxing with 500 ml. of 90–100° ligroin, and the hot solution is decanted from the sodium carbonate onto a fluted filter. This process is repeated with three 150-ml. portions of ligroin. The combined filtrates are concentrated to 500 ml., filtered if necessary, and cooled to 0°. The acid chloride is collected on a Büchner funnel and pressed as dry as possible. It is washed twice with 30–60° petroleum ether and stored in a vacuum desiccator over phosphorus pentoxide and paraffin shavings (Note 6). The yield of orange-red crystals melting at 94.5–95.5° is 48 g. (89%).
2. Notes
1.
The checkers found that 50 g. of unrecrystallized acid gave
45 g. of acid chloride melting at
92–94°. When this was recrystallized from 90–100°
petroleum ether (10 ml. per g.),
41.5 g. of orange-red crystals melting at
94.5–95.5° was obtained. The over-all yield of pure acid chloride on the basis of unrecrystallized acid is the same. The use of unrecrystallized acid has an advantage in that the volume of solvent required for recrystallization of the acid chloride is much less than for the acid.
2.
The use of
sodium carbonate is unusual. It is claimed that the
sodium carbonate prevents decomposition and tar formation during the reaction.
3.
The checkers used
Eastman Kodak Company's best grade of thionyl chloride.
4.
Refluxing should be carried out under a
hood or in an apparatus provided with a
gas trap.
5.
About
170 ml. of good thionyl chloride can be recovered.
6.
The acid chloride holds the
petroleum ether tenaciously. About a week is required for complete removal of the
petroleum ether.
3. Discussion
p-Phenylazobenzoyl chloride (azoyl chloride) has been prepared by the action of
thionyl chloride on the acid.
1,2 The method used is a modification of that of Ladenburg, Fernholz, and Wallis.
2
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
ligroin
petroleum ether
azoyl chloride
thionyl chloride (7719-09-7)
sodium carbonate (497-19-8)
phosphorus pentoxide (1314-56-3)
p-Phenylazobenzoic acid (1562-93-2)
p-Phenylazobenzoyl chloride,
Benzoyl chloride, p-phenylazo- (104-24-5)
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