Laurolactam
Laurolactam is an organic compound from the group of macrocyclic lactams. Laurolactam is mainly used as a monomer in engineering plastics, such as nylon-12 and copolyamides. Synthesis. Although a derivative of 12-aminododecanoic acid, it is made from cyclododecatriene. The triene is hydrogenated to the saturated alkane, cyclododecane. For the production of laurolactam, cyclododecane is oxidized with air or oxygen in the presence of boric acid and transition metal salts (e.g. cobalt(II) acetate), obtaining a mixture of cyclododecanol and cyclododecanone. This mixture is quantitatively dehydrogenated on a copper contact catalyst to cyclododecanone and this reacted with hydroxylamine to cyclododecanone  oxime. The oxime is rearranged to laurolactam in a Beckmann rearrangement in the presence of a strong acid. An alternative process is the photonitrosation of cyclododecane with nitrosyl chloride in the presence of anhydrous hydrogen chloride. The resulting cyclododecanone oxime is extracted with concentrated sulfuric acid and rearranged to laurolactam by heating to 160 °C. The overall yield (photonitrogenation + Beckmann rearrangement) is up to 93%. Properties. Laurolactam is a water-insoluble, crystalline solid; in technical quality usually beige colored and in pure state (99.9% purity) white. It is soluble in many organic solvents, e. g. 1,4-dioxane, benzene  or cyclohexane. The purification process is carried out conventionally by multistage distillation under reduced pressure. The combination of distillation and crystallization from solution or melt yields very pure laurolactam (> 99%). The risk posed by laurolactam is considered to be low. Uses. Ring opening polymerization is used to polymerize the monomer to nylon-12. The reaction can be brought about with cationic or anionic initiators or with water. Cationic polymerization with acid is believed to involve the initial O-protonation. Nucleophilic attack by the monomer on the reactive protonated nitrogen, followed by successive ring-opening acylation of the primary amine results  in the formation of the polyamide. The ring-opening polymerization of the monomer laurinlactam initially proceeds upon addition of water in a pre-polymerization at about 300 °C under pressure to a prepolymer. This prepolymer is reacted in a subsequent polycondensation at ambient or reduced pressure and temperatures of about 250 °C to higher molecular weight polyamide 12 ( PA 12: -[NH-(CH)-CO]-). As a comonomer, laurolactam is used together with ε-caprolactam for the preparation of copolyamide 6/12.