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 molecular orbital calculations at the QCISD(T)/6-31 G∗//UMP2(full)/6-31G∗ + ZPE level. At low internal energy 1·+ isomerizes into the distonic ion, [NH2CHCH2NH3]·+, 2·+ which, further, dissociates by ammonia loss. The 1,3-hydrogen migration, 1·+ → 2·+, is the energy determining step of the fragmentation. Ions of higher internal energy rapidly dissociate by a simple C–C bond cleavage. As confirmed by RRKM statistical calculations, this system provides a clear example of the influence of the internal energy on the competition between rearrangement and simple bond rupture.