The origin of alkenes in illicit amphetamine: An examination of the illicit synthesis of phenyl-2-propanone

The acylative decarboxylation reaction of phenylacetic acid, a method used in clandestine laboratories for the synthesis of phenyl-2-propanone, has been examined. It has been demonstrated that this reaction is accompanied by side- reactions that produce characteristic neutral compounds; some of these are cis and trans 1,3-diphenyl-2-methylpropene and the enol acetates derived from dibenzylketone and phenyl-2-propanone. It would be difficult for an unskilled chemist to separate these neutral substances from phenyl-2-propanone, therefore illicit phenyl-2-propanone is likely to be an impure product. The use of crude phenyl-2-propanone in reductive amination reactions aimed at amphetamine production gives rise to a complex mixture of amines and characteristic neutral compounds. The likely origins of N-acetylamphetamine and amphetamine benzaldimine are also discussed.