Structure and fragmentation mechanism of [C 3 H 7 S] + ions

From a comparison of the metastable ion bundance ratios for loss of C 2 H 4 and H 2 S from [C 3 H 7 S] + ions in a series of alkyl thio ethers and thiols it was concluded that in most compunds these ion s isomerize to a common structure prior to decomposition in the first field free region. The mechanism for C 2 H 4 loss from the [C 3 H 7 S] + ion gen erated from CH 3 SCH 2 CH 3 was investigated in detail using 13 C and 2 H labelling. A rearrangement with formation of a cyclic intermediate prior to the decompistion reaction is proposed. The fragmentation is preceded by extensive hydrogen scrabling. The carbon atoms of the expelled C 2 H 4 molecule are those of the CH 2 CH 3 moiety.