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A Detailed Mechanistic Fragmentation Analysis of Methamphetamine and Select Regioisomers by GC/MS
Author(s) -
Sachs Sandra B.,
Woo Francis
Publication year - 2007
Publication title -
journal of forensic sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.715
H-Index - 96
eISSN - 1556-4029
pISSN - 0022-1198
DOI - 10.1111/j.1556-4029.2007.00401.x
Subject(s) - structural isomer , fragmentation (computing) , electron ionization , chemistry , mass spectrum , ion trap , computational chemistry , mass spectrometry , ion , methamphetamine , molecule , ionization , stereochemistry , chromatography , computer science , organic chemistry , operating system , medicine
A novel ring‐substituted methamphetamine regioisomer, N ,α,4‐trimethyl phenmethylamine, was synthesized in order to study the validity of proposed structures for various mass spectrometry (MS)‐derived peaks in a methamphetamine fragmentation pattern. While other research efforts have studied aspects of methamphetamine in detail, a full fragmentation study has not been reported previously. In addition to showing molecular structures represented by fragment peaks, mechanisms for selected processes are detailed. An empirically derived procedure to easily determine by simple spectral peak pattern recognition the geometry of dimethyl‐ or ethyl‐substituted immonium ions (RRC=N + RR) where m/z =58 is outlined. These results are platform independent for electron ionization (EI) instruments, but have also proven to be helpful in explaining spectral peaks observed in spectra from ion trap systems. The spectrum for the synthesized methamphetamine regioisomer was accurately predicted using this methodology. While this approach is useful in some casework, the converse may be more useful: when an unexpected or unusual peak pattern arises in a spectrum, being able to analyze it to determine the structure of the molecule. This paper gives an analyst the means to begin such retro‐synthetic analyses.