The gas enhanced negative ion mass spectra of polychloroanisoles

Methane or a methane–oxygen mixture was used as an enhancement gas to obtain negative ion mass spectra of polychloroanisoles. Dichloroanisoles did not react with oxygen but the more highly chlorinated anisoles did. Compounds with hydrogen ortho to the methoxy group had [M? 1]^? ions, while others gave . The fragment arose through loss of an ortho chlorine and amethyl hydrogen. The loss of HCl followed by oxygen displacement of a remaining ortho or para chlorine produced [M? 55]^? ions; the para position was the preferred site of displacement. Another ion-molecule reaction with oxygen leads to [M? CH₂Cl]^?. The fragmentations resemble those of chlorinated aromatics such as the polychlorodibenzodioxins.