REARRANGEMENT AND DISSOCIATION OF IONIZED 1,2-DIAMINOETHANE

The chemistry of ionized 1,2-diaminoethane, [NH2CH2CH2NH2](.+), 1(.+) is studied by means of tandem mass spectrometry techniques and molecul ar orbital calculations at the QCISD(T)/6-31 G//UMP2(full)/6-31G* + Z PE level. At low internal energy 1(.+) isomerizes into the distonic io n, [NH2CHCH2NH3](.+), 2(.+) which, further, dissociates by ammonia los s. The 1,3-hydrogen migration, 1(.+) --> 2(.+), is the energy determin ing step of the fragmentation. Ions of higher internal energy rapidly dissociate by a simple C-C bond cleavage. As confirmed by RRKM statist ical calculations, this system provides a clear example of the influen ce of the internal energy on the competition between rearrangement and simple bond rupture. (C) 1998 Elsevier Science B.V.