GC–MS and GC–IR of regioisomeric 4-N-methoxy- and dimethoxybenzyl derivatives of 3-trifluoromethylphenylpiperazine

Abstract

A series of nine N,N-disubstituted piperazines were synthesized containing the structural elements of 3-trifluoromethylphenylpiperazine (3-TFMPP) in combination with each of the three regioisomeric monomethoxybenzyl-, and six regioisomeric dimethoxybenzyl substituents to yield the nine N,N-disubstituted piperazine compounds. These nine potential designer drug analogues were prepared based on common designer modifications of the known novel psychoactive substance 3-TFMPP and compared in GC–MS and GC–IR studies. The GC separation on an Rxi®-17Sil MS stationary phase showed the regioisomers of the methoxybenzyl to elute according to the position of aromatic ring substitution with the 2- isomer eluting before the 3-isomer and the 4- methoxybenzyl isomer eluting last. The six regioisomeric dimethoxybenzyl analogues eluted according to the degree of substituent crowding with the 2,3- and 2,6-isomers eluting first and the 3,5-isomer last. Numerous EI mass spectral fragment ions occur via processes initiated by one of the two nitrogen atoms of the piperazine ring. The major EI-MS fragment ions are at m/z 229 observed in all nine spectra occurs from the loss of the substituted benzyl radical and the m/z 56 cation (C3H6N)+ originates from the piperazine ring. Other characteristic fragments containing the benzyl portion of these analogues show a 30 Da variation based on the number of methoxy group substituents. The relative intensity of ions in the methoxybenzyl series as well as some unique ions in the dimethoxybenzyl series provides initial points of preliminary differentiation. These results coupled with characteristic vapor phase infrared spectra allow for the identification of each regioisomer.