The mass spectrometry of DT-and monosubstituted biphenyls: Dependence of fragmentation patterns on position of substitution

This paper describes the mass spectroscopy of a series of biphenyl derivatives substituted in the 2,2′, 4,4′ and 2 positions. The substitutent functional groups are carbomethoxy, carbothoxy, carboxylic acid and hydroxymethyl. In addition, some results are reported on the spectroscopy of the d₅-carboethoxy derivatives, the 2- and 2,2′-αd₂- hydroxymethyl derivatives and fluorene-4-methanol. The molecular ions of the 4,4′-disubstituted biphenyl derivatives are far more stable than those of the 2,2′ isomers. It is also observed that the fragmentation patterns of these two sets of isomers are sharply different. Paradoxically, the 2-substituted biphenyl derivatives give relatively stable molecular ions and their fragmentation patterns are frequently different from those of the corresponding 2,2′-disubstituted biphenyls. The bulk of the evidence presented in this paper suggests that the usual sort of ‘ortho effect’ is not a significant factor in the fragmentation mechanisms proposed for the 2,2′-disubstituted biphenyl derivatives.