Der Einfluß der Kettenlänge auf die massenspektrometrigche Fragmentierung höherer 1.ω-Diphenylalkane / The Influence of the Chain Length on the Mass Spectrometric Fragmentation of Higher 1, ω-Diphenylalkanes

Abstract

The mass spectrometric fragmentation of 1,ω-diphenylalkanes (2 ≤ ω ≤ 22) has been studied in order to elucidate the effect of the chain length on the reactions of unstable and metastable molecular ions with respect to the occurrence of internally solvated ions in the gas phase. The unstable molecular ions of all 1,ω-diphenylalkanes react predominantly by formation of C7H7 + and C7H8 + ions, the latter ones are also formed by metastable molecular ions. Neither the variation of the relative abundances of these fragment ions with the chain length nor the fragmentation of specifically deuterated molecular ions indicate any internal solvation in the reacting ions. Inspite of the localized activated C-H bonds at the benzylic positions, these “activated” H atoms are not involved in intra­molecular hydrogen exchange reactions or the formation of C7H8 + ions (with the exception of ω = 3). Especially the higher homologues (co ≿ 12) react very similarly to the molecular ions of 1-phenylalkanes, while the fragmentation of the lower homologues (co ≲ 6) is determined by specific (“vinculoselective”) competitive reactions, e.g. loss of C7H7 and C8H8.