title: Unique para-effect in electron ionization mass spectra of bis(perfluoroacyl) derivatives of bifunctional aminobenzenes.
abstract: A new kind of 'para-effect' under electron ionization (EI) conditions has been discovered for a series of bis(perfluoroacyl) derivatives of o-, m- and p-phenylenediamines, -hydroxybenzeneamines and -mercaptobenzeneamines of a common structure RCOX-C(6)H(4)-NHCOR (X = NH, S, O; R = CF(3), C(2)F(5), C(3)F(7)). Only the para-isomers showed successive loss of a radical RCO* and a molecule RCN, leading to very intense peaks in the EI spectra. The composition and the origin of the [M-COR-NCR](+) ions were confirmed by exact mass measurements and linked scan experiments. The proposed mechanism of their formation takes into account likely para-quinoid structures of the precursor ions. A similar rearrangement has not been observed for para-isomers in the series of bis(perfluoroacyl) derivatives of benzenediols, mercaptophenols and dimercaptobenzenes.
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA. kirill.tretyakov@nist.gov
authors.forename: Kirill V
authors.initials: KV
authors.lastname: Tretyakov
authors.forename: Nino G
authors.initials: NG
authors.lastname: Todua
authors.forename: Roman S
authors.initials: RS
authors.lastname: Borisov
authors.forename: Vladimir G
authors.initials: VG
authors.lastname: Zaikin
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Stein
authors.forename: Anzor I
authors.initials: AI
authors.lastname: Mikaia