Analytical Chemistry and Spectroscopy
Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
N-(2-Propynyl)anilines undergo amino-Claisen rearrangement to a minor extent in the ion source, losing a molecule of HCN under electron impact conditions. However, metastable molecular ions with energies closer to threshold undergo Claisen rearrangement giving rise to more abundant [M - HCN]+· ions in the first field-free region. Loss of a hydrogen from the molecular ion gives rise to the base peak in the mass spectrum of N-(2-propynyl)aniline. The hydrogen that is expelled for the formation of the [M - H]+ ion is observed to be from the amino nitrogen, propargylic carbon and the ortho-carbon of the ring. The last process leads to a cyclic fragment involving intramolecular aromatic substitution. Double oxygen migration from the nitro group to the triple bond, due to the ortho effect, yields an abundant ion at m/z 105 in N-(2-propynyl)-o-nitroaniline. The proposed fragmentation pathways and ion structures are substantiated by high-resolution data, B/E and B2/E linked-scan spectra, collisionally activated dissociation-B/E linked-scan spectra and deuterium isotopic labelling.
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