DE1695253

o -Dodecalactam, or its mixture with e -caprolactam is made by subjecting cyclododecanone oxime or its mixture with cyclohexanone oxime respectively to Beckmann rearrangement in the presence of e -caprolactam, which may be added as such or formed by the rearrangement of cyclohexanone oxime, as solvent. Suitably a mixture of cyclohexanone and cyclododecanone is converted into a mixture of cyclohexanone oxime and cyclododecanone oxime preferably by reaction with a hydroxylamine salt at a pH of 3-6 and a temperature of 80-110 DEG C. and the product is subjected to Beckmann rearrangement, for example, by reaction with concentrated sulphuric acid oleum or phosphoric acid which may contain free P2O5. The lactam products may be separated by distillation and the e -caprolactam recycled and used again as a solvent in oxime formation and Beckmann rearrangement.