Analysis of pyrolysis products of methamphetamine.

This study examined the pyrolysis products of d-methamphetamine (d-MA) and the pyrolysis mechanism. A sealed glass tube, in which MA-HCl was placed, was wrapped with pyrolysis-foil and heated at the Curie point of the pyrolysis-foil. The pyrolysis products of MA were detected by gas chromatography-mass spectrometry and liquid chromatography-electrospray ionization-mass spectrometry. MA-d(3)-HCl, in which all the hydrogen atoms of N-methyl group of MA were substituted with deuterium atoms, was pyrolyzed to investigate the transformation of a methyl group of MA. Amphetamine (AM) and dimethylamphetamine (DMA) were produced via demethylation and methylation reactions, respectively, at temperatures above 315 degrees C. The demethylation and methylation reactions were the major pyrolysis processes at temperatures below 358 degrees C. At temperatures above 315 degrees C, the reaction of DMA with a methyl group eliminated from the methylamino group of MA resulted in the formation of benzylethyltrimethylammonium (BEMA). This transformation reveals that demethylation and methylation reactions occur in the form of a methyl cation. The thermal degradation of BEMA, the abstraction of a proton at the beta-position and the elimination of a trimethylamine, produced allylbenzene, cis-beta-methylstyrene, and trans-beta-methylstyrene at temperatures above 315 degrees C. At temperatures above 445 degrees C, the optical isomers, or l-isomers of AM, MA, and DMA, were produced as pyrolysis products.