EFFECTS OF PHENYL SUBSTITUTION ON THE FRAGMENTATION OF STERICALLY CONGESTED DI-TERT-BUTYLSTILBENE RADICAL CATIONS

The characteristic mass spectrometric fragmentation patterns of steric ally congested stilbenes, phenyl-substituted 2,2,5,5-tetramethyl-3,4-d iphenylhex-3-enes, are described. In contrast to stilbene, these steri cally congested stilbenes show facile loss of tert-butyl and/or isobut ene and phenyl, ultimately leading to ions with the constitution of di substituted acetylenes. The isobutene/tert-butyl ratio increases as su bstituents attached to the phenyl ring become more electronegative.