Eventually these chains will undertake further complex reactions to result in e.g., polymers such as amorphous carbon and C60, the energetics of which will be investigated in future work. The final transition states investigated are those involving reaction of 2 with a solvent such as dichloromethane, in which the original solution experiments were performed. Predominant trapping of 2 by other species such as galvinoxyl would require the barrier for reaction with solvent to be significantly higher than with the trap, especially since the concentration of the solvent is much greater (~12M) than that reported for the trapping species (~0.02-0.033M). The bimolecular reaction between 2 and dichloromethane involves hydride abstraction to give an acetylide anion and a 1,1-dichloromethylium cation (no biradical character was detected). The transition state (Figure ) for 1,2-substitution corresponds to a reaction free energy barrier of 33.3 kcal mol -1 , which is high enough to preclude facile reaction of 2 with 12M solvent, as observed. Contrast this with the free energy barrier calculated for reaction of singlet free C2 itself with dichloromethane (Figure ), which is very much lower (DG298 ‡ 10.7 kcal mol -1 or 15.6 kcal mol -1 for the lowest triplet state of C2, Table ). If unbound C2 were indeed to be generated in dichloromethane solutions at ambient temperatures, a free energy barrier this low would certainly mean its rapid trapping by the solvent.