An energy‐resolved study of the fragmentation of ionized 1‐Penten‐3‐ol

A detailed energy‐resolved study of the fragmentation of CH 2 CHCH(OH)CD 2 CD 3 (1‐ d 5 ) has been carried out using metastable ion studies and charge exchange techniques, combined with collision‐induced dissociation studies to establish the structures of fragment ions. At low internal energies (metastable ions) the molecular ion of 1‐ d 5 rearranges to the 3‐pentanone structure and fragments by loss of C 2 H 5 or C 2 D 5 leading to the acyl structure, [CH 3 CH 2 CO] + or [CD 3 CD 2 CO] + , for the fragment ion. However, with increasing internal energy of the molecular ion this rearrangement process decreases rapidly in importance and loss of C 2 D 5 by direct cleavage, leading to [CH 2 CHCHOH] + , becomes the dominant fragmentation reaction. As a result the [C 3 H 5 O] + ion seen in the electron impact mass spectrum of 1‐penten‐3‐ol has predominantly the protonated acrolein structure.