(
B)
ε-Benzoylaminocaproic Acid.—The rearrangement of
100 g. (0.88 mole) of pure cyclohexanone oxime (Note
3) is carried out in the following way. In a
1-l. beaker are placed a
10-g. portion of the oxime and
20 cc. of 85 per cent sulfuric acid (sp. gr. 1.783) (Note
4). The beaker is heated with a low flame and the contents are mixed with a rotary motion until bubbles first appear. The beaker is then removed from the flame immediately, and the violent reaction, which lasts a few seconds, is allowed to subside. The acid solution of
ε-caprolactam is transferred to a
5-l. round-bottomed flask, and another
10-g. portion of the oxime is placed in the beaker and rearranged with
sulfuric acid as before. The combined acid solution from the ten operations is diluted with 2.5 l. of water and boiled gently for one and one-half hours with
5 g. of decolorizing carbon. The solution is filtered and exactly neutralized to litmus with
50 per cent sodium hydroxide solution. About
510 g. of sodium hydroxide solution is usually required. The neutral solution is boiled for one-half hour with
5 g. of decolorizing carbon and filtered.
The filtrate is placed in a 5-l. flask fitted with a mechanical stirrer, cooled in an
ice bath to 10°, and a solution of
55 g. (1.37 moles) of sodium hydroxide in 55 cc. of water added. The temperature being kept at 10°,
94 g. (0.67 mole) of benzoyl chloride is added dropwise from a
separatory funnel over a period of thirty-five to forty minutes, with rapid stirring. The mixture is stirred for an hour longer, filtered, and placed in a
4-l. beaker. The cold filtrate is slowly acidified to
Congo red by adding
10 per cent hydrochloric acid, with hand stirring (about 450 cc. of acid is required). The solid (Note
5) is filtered with suction, washed with water, and spread out to dry. When dry, the product is washed with two
100-cc. portions of petroleum ether (35–60°) to remove the admixed
benzoic acid. The adhering
petroleum ether is allowed to evaporate from the crystals, and the final drying is carried out in a
vacuum desiccator over
sulfuric acid. The yield of purified product, m.p.
77–80°, is
135–150 g. (
65–72 per cent of the calculated amount, based on
cyclohexanone oxime).