When the reaction again drops to 25" C., add the reaction liquor to 400 cc. of vigorously stirred petroleum ether. A heavy oil separates, which on further stirring hardens to a light cream-colored solid. Filter this solid in a dry box through a filtered glass funnel, to recover 42.7 grams of product.This product is further purified by redissolution in fresh dichloroethane and reprecipitation with fresh petroleum ether. The purified material is dried in the dry box and is extremely hygroscopic. I n fact, if a very well dried stream of nitrogen is not employed in the dry box, it turns into a puddle in a matter of hours. The product was analyzed for C, H, and S and checked almost exactly for caprimidyl sulfate. This solid has a melting point of 122" C. as compared with 88" C. for cyclohexanone oxime, and 67-C. for caprolactam. I t can be converted quantitatively to caprolactam by treatment with sodium hydroxide. To demonstrate that this solid was not caprolactam sulfate, the sulfate was prepared from known caprolactam. The physical properties and behavior of the two products were entirely different.If desired, 36.6 grams of triethyl phosphate (0.2 mole) can be used in place of the 17.6 grams of dioxane. This gives a liquid rather than a solid complex specie.
ConclusionsCaprolactam can now be prepared in good yields under mild and safe conditions a t low temperatures by use of phosphate or dioxane complexed SOa. Caprimidyl sulfate has been isolated as a new composition of matter. I t is a very hygroscopic but stable white solid, melting a t 122" C. Other ketoximes can be used but aldoximes undergo dehydration rather than rearrangement. Aromatic ketoximes can be rearranged by phosphate complexed SO3 without ring sulfonation.