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Hydride transfer reactions via ion–neutral complex: fragmentation of protonated N ‐benzylpiperidines and protonated N ‐benzylpiperazines in mass spectrometry
Author(s) -
Chai Yunfeng,
Jiang Kezhi,
Pan Yuanjiang
Publication year - 2010
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/jms.1731
Subject(s) - chemistry , protonation , hydride , substituent , fragmentation (computing) , medicinal chemistry , photochemistry , mass spectrometry , computational chemistry , ion , organic chemistry , chromatography , computer science , operating system , hydrogen
An ion‐neutral complex (INC)‐mediated hydride transfer reaction was observed in the fragmentation of protonated N ‐benzylpiperidines and protonated N ‐benzylpiperazines in electrospray ionization mass spectrometry. Upon protonation at the nitrogen atom, these compounds initially dissociated to an INC consisting of [RC 6 H 4 CH 2 ] + (R = substituent) and piperidine or piperazine. Although this INC was unstable, it did exist and was supported by both experiments and density functional theory (DFT) calculations. In the subsequent fragmentation, hydride transfer from the neutral partner to the cation species competed with the direct separation. The distribution of the two corresponding product ions was found to depend on the stabilization energy of this INC, and it was also approved by the study of substituent effects. For monosubstituted N ‐benzylpiperidines, strong electron‐donating substituents favored the formation of [RC 6 H 4 CH 2 ] + , whereas strong electron‐withdrawing substituents favored the competing hydride transfer reaction leading to a loss of toluene. The logarithmic values of the abundance ratios of the two ions were well correlated with the nature of the substituents, or rather, the stabilization energy of this INC. Copyright © 2010 John Wiley & Sons, Ltd.