The mass spectrometry ofO-alkyl-N-arylsulfonyl carbamates

Abstract

We report the mass spectra of a series of O-alkyl-N-p-toluenesulfonyl carbamates with the following alkyl substituents: methyl, ethyl, n-propyl, isobutyl, neopentyl, β-phenethyl, isopropyl, sec-butyl, cyclohexyl, α-phenethyl, tert-butyl and tert-amyl. The fragmentation of the primary and secondary alkyl substituents involves a rearrangement accompanied by the loss of SO2 followed by fragmentation of the [M – 64] radical-ion to produce cresol as one of the principal fragments. The [M – 64] fragment of branched alkyls also undergoes a McLafferty rearrangement to yield either O-p-tolyl carbamate or N-p-tolyl carbamic acid and the corresponding olefin. In contrast, O-tert-alkyl-N-arylsulfonyl carbamates yield fragmentation patterns similar to those observed for N-tert-alkyl arylsulfonamides. The spectrum of O-tert-butyl-N-p-methoxybenzenesulfonyl carbamate exhibits strong [M – 44] and [M – 59] peaks which correspond to the loss of CO2 followed by a methyl radical from the molecular ion. Introduction of methyl groups either to the sulfonyl carbamate nitrogen atom or the ortho positions of the aryl substituent of O-tert-butyl derivatives forces the molecular ion to rearrange with a loss of SO2 instead of CO2.