Using highly correlated ab initio methods, a new transition state is characterized in the lowest singlet potential energy surface of HCCH(++). This transition state possesses a dibridged (or "butterfly") form not observed yet for any acetylic compound. It can be reached either directly or after spin-orbit conversion of triplet HCCH(++) ions. In light of these calculations, a reaction pathway for the proton pair formation (i.e., HCCH(++)-->C(2)+H(+)+H(+)) is proposed.