Editing Caprolactam (section)

==Synthesis and production==
Caprolactam was first described in the late 1800s when it was prepared by the cyclization of ε-[[aminocaproic acid]], the product of the hydrolysis of caprolactam. World demand for caprolactam was estimated to reach five million tons per year for 2015. 90% of caprolactam produced is used to make filament and fiber, 10% for plastics, and a small amount is used as a chemical intermediate.<ref name = Ullmann/> Due to its commercial significance, many methods have been developed for the production of caprolactam. It was estimated that 90% of all caprolactam is synthesised from [[cyclohexanone]] ('''1'''), which is first converted to its [[Cyclohexanone oxime|oxime]] ('''2'''). Treatment of this oxime with acid induces the [[Beckmann rearrangement]] to give caprolactam ('''3'''):<ref name=Ullmann/>

: [[File:Beckmann-rearangement (cropped).png|350px|The Beckmann Rearrangement]]

The immediate product of the acid-induced rearrangement is the bisulfate salt of caprolactam. This salt is neutralized with [[ammonia]] to release the free lactam and cogenerate [[ammonium sulfate]]. In optimizing the industrial practices, much attention is directed toward minimizing the production of ammonium salts.<ref name = Ullmann/>

The other major industrial route involves formation of the oxime from [[cyclohexane]] using [[nitrosyl chloride]], and this method accounts for 10% of world production.<ref name = Ullmann/> The advantage of this method is that cyclohexane is less expensive than [[cyclohexanone]].

A minor industrial route involves the treatment of [[cyclohexanecarboxylic acid]]  with [[nitrosylsulfuric acid]] (the Snia Viscosa process). This is thought to proceed via a [[ketene]].

:[[File:Nitrosodecarboxylation_Caprolactam_Synthesis.svg|500px]]

Other paths to caprolactam include the depolymerization of waste Nylon 6, and the reaction of [[caprolactone]] with ammonia.<ref name=Ullmann/> At bench scale, the reaction between cyclohexanone with [[hydrazoic acid]] to give caprolactam in the [[Schmidt reaction]] has been reported.<ref>{{cite journal | doi = 10.1016/S0040-4020(00)00218-0 | journal = Tetrahedron | title = Expansion to Seven-Membered Rings | author1 = Eric J. Kantorowski  | author2 = Mark J. Kurth | volume = 56 | issue = 26 | pages = 4317–4353 | year = 2000}}</ref>

:[[File:Schmidt ring expansion.png|600px]]