Collisional activation study of cyclic polysulfides

Abstract

Abstract Cyclic polysulfides isolated from higher plants, model compounds and their electron impact induced fragment ions have been investigated by various mass spectrometric methods. These species represent three sets of sulfur compounds: C 3 H 6 S x ( x =1−6), C 2 H 4 S x ( x =1−5) and CH 2 S x ( x =1−4). Three general fragmentation mechanisms are discussed using metastable transitions: (1) the unimolecular loss of structural parts (CH 2 S, CH 2 and S x ); (2) fragmentations which involve ring opening reactions, hydrogen migrations and recyclizations of the product ions ([MCH 3 ] + , [MCH 3 S] + , [MSH] + and [MCS 2 ] +˙ ); and (3) complete rearrangements preceding the fragmentations ([MS 2 H] + and [MC 2 H 4 ] +˙ ). The cyclic structures of [M] +˙ and of specific fragment ions have been investigated by comparing the collisional activation spectra of model ions. On the basis of these results the cyclic ions decompose via linear intermediates and then recyclizations of the product ions occur. The stabilities of the fragment ions have been determined by electron efficiency vs electron energy curves.