THE REMARKABLE ELECTRON-IMPACT MASS-SPECTRUM OF (2-BENZYL-1,3-XYLYLENE)-15-CROWN-4 - EXPULSION OF TRIETHYLENE GLYCOL BY DOUBLE HYDROGEN-TRANSFER

During our investigations of the synthesis of magnesium-containing cro wn ethers, the mass spectral characterisation of a precursor, (2-benzy l-1,3-xylylene)-15-crown-4 (C21H26O4), leads to a surprising result: i ts electron-impact mass spectrum was nearly identical with that of 1-m ethylanthracene, C15H12. Several deuteriated analogues and other model compounds were synthesised and investigated with respect to their ion isation-induced and collision-induced mass spectroscopic behaviour. A mechanism for the fragmentation of the ions of [2-benzyl-1,3-xylylene] -15-crown-4 to a [C15H12H12](.+) species is proposed. It involves cons ecutive 1,5-H transfer, to generate an open-chain polyether group, cyc lisation of the two aromatic moieties, to give an anthracene-type inte rmediate, and remote hydrogen transfer, to release the triethylene gly col neutral.