Reactivity of collisionally activated dichlorocarbene dications studied by tandem mass spectrometry.

The dissociation mechanisms of dichlorocarbene dications following collisional activation have been investigated via tandem mass spectrometric techniques and semi-empirical calculations. Three channels appear to be significant: {fx1019-1} The second channel becomes dominant at high internal energy. Production of ground state fragments (channel 1) involves a transition driven by spin-orbit coupling from the CCl 2 (2+) [Formula: see text] state to the CCl 2 (2-) ā(3)Σ u (-) state en route to the fragments. The dissociation barrier for the production of ground state fragments from the ground electronic state of CCl 2 (2+) via the spin-orbit-induced transition is equal to 420 kJ mol(-1). The dissociation pathway that corresponds to channel 3 includes a first isomerization step from the linear Cl-C-Cl(2+) structure to a bent Cl-Cl-C(2+) connectivity. The calculated isomerization barrier amounts to 550 kJ mol(-1). The calculated reverse activation barriers are compatible with the measured kinetic energy released on the fragments.