Water-assisted isomerization from linear propargylium (H2CCCH+) to cyclopropenylium (c-C3H3+)

Calculations at the QCISD(T)/6-311+G(d,p)//B3LYP/6-31G(d) level indicate that the participation of water can effectively lower the isomerization barrier from linear propargylium (H2CCCH+) to cyclopropenylium (c-C3H3+), With the increase of the amount of H2O (nH(2)O, n = 1, 2, or 3) participating in the isomerization, the isomerization barrier decreases, and with three H2O molecules the isomerization becomes nearly barrierless. In contrast to previous studies on the catalytic effects of water on carbonyl systems and the reaction of H2O(g) with SO3(g), the so-called reactant and the catalyst do not associate into cyclic structures, but rather into open-chain structures. This work may be useful for further studies on the catalytic effect of other species having lone electronic pairs, such as H2S, NH3, and HF.