Substituent Effect on Fragmentations and Ion-Molecule Reactions of Ionized Alkyn Alcohols

Abstract

The fragmentation patterns and ion-molecule reactions of two alkyn alcohols, 2-propyn-1-ol (HC≡CCH 2 OH) and 2-methyl-3-butyn-2-ol (HC≡CC(CH 3 ) 2 OH), were investigated using Fourier transform mass spectrometry (FTMS). The most abundant fragment ions formed from the molecular ions were [M-H] + for 2-propyn-1-ol and [M-CH 3 ] + for 2-methyl-3-butyn-2-ol. The dehydrated ion, [M-H 2 O] + was formed only from 2-propyn-1-ol in which α-hydrogen atoms were available for α,α-elimination reaction. The protonated molecules were dissociated into [M+H-H 2 O] + and [M+H-C 2 H 2 ] + through dehydration and deacetylenylation processes. The formations of [M+H-H 2 O] + and [M+H-C 2 H 2 ] + from 2-methyl-3-butyn-2-ol were more favorable than those from 2-propyn-1-ol due to stabilization by two methyl groups at α-carbon. Ion-neutral complexes formed at long ion trapping time gave dehydrated and/or deacetylenylated ion products by further dissociation.