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Vapor phase infrared identification of regioisomeric N-(dimethoxybenzyl)-4-iodo- and 4-bromo-2,5-dimethoxyphenethylamines

NCJ Number
Forensic Chemistry Volume: 19 Dated: 2020
Date Published

This study used vapor phase infrared spectroscopy to provide data for the differentiation of the individual regioisomers of the six N-(dimethoxybenzyl)-4-iodo-2,5-dimethoxyphenethylamines and the six N-(dimethoxybenzyl)-4-bromo-2,5-dimethoxyphenethylamines.


These compounds differ from the traditional N-(2-methoxybenzyl)-4-iodo- and 4-bromo-2,5-dimethoxyphenethylamines (25I- and 25B-NBOMe) by the addition of one methoxy group into the N-methoxybenzyl molecular framework. The vapor phase infrared spectra obtained directly as the compounds elute from the GC column provide data for the identification of any one of these regioisomeric compounds to the exclusion of the other five substances of mass spectral equivalence. The spectra are derived from the compounds in the free base form at temperatures preventing interference from water vapor, intermolecular interactions such as polymorphism or other related issues of salt form and/or relative crystallinity. Fragment ions in the electron ionization mass spectra of these compounds identify the nature of the halogen (I or Br) but not the position of substitution of the methoxy groups on the benzyl aromatic ring. These compounds are composed of two separate and distinct ring systems, the halogenated phenethylamines 4-iodo-2,5-dimethoxyphenethylamine and 4-bromo-2,5-dimethoxyphenethylamine and a second ring system consisting of the six positional isomers of dimethoxybenzylamine. Major absorption bands resulting from aromatic ring C–C and C–O stretching vibrations provide data for differentiation of the benzyl ring substitution pattern. Model compounds representing all the single ring systems provide significant structural correlation with the vapor phase infrared spectra for these regioisomeric NBOMe derivatives. (publisher abstract modified)

Date Published: January 1, 2020