Description:
<jats:title>Abstract</jats:title><jats:p><jats:italic>N</jats:italic>‐(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]<jats:sup>+·</jats:sup> 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 <jats:italic>N</jats:italic>‐(2‐propynyl)aniline. The hydrogen that is expelled for the formation of the [M − H]<jats:sup>+</jats:sup> ion is observed to be from the amino nitrogen, propargylic carbon and the <jats:italic>ortho</jats:italic>‐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 <jats:italic>ortho</jats:italic> effect, yields an abundant ion at <jats:italic>m</jats:italic>/<jats:italic>z</jats:italic> 105 in <jats:italic>N</jats:italic>‐(2‐propynyl)‐<jats:italic>o</jats:italic>‐nitroaniline. The proposed fragmentation pathways and ion structures are substantiated by high‐resolution data, <jats:italic>B</jats:italic>/<jats:italic>E</jats:italic> and <jats:italic>B</jats:italic><jats:sup>2</jats:sup>/<jats:italic>E</jats:italic> linked‐scan spectra, collisionally activated dissociation–<jats:italic>B</jats:italic>/<jats:italic>E</jats:italic> linked‐scan spectra and deuterium isotopic labelling.</jats:p>