Reaction pathway for formation of c-C₃ (CN)₂ from c-C₃ HCN and -CN. I1 and I2 refer to intermediates 1 and 2, respectively. TS refers to a transition state, and the intermediate type involved in the transition is noted as a subscript. Dashed lines indicate procession across electronic states. All associations are assumed to require intersystem crossing to proceed but are indicated with solid lines for clarity. Relative energies in kcal mol^–1.