The energies of cyclobutyne, perfluorocyclobutyne and related compounds have been calculated at levels from MP2/6-31G* through QCISD(T)/6-311+G*, and also at B3LYP and B3PW91/6-311+G*. The relative energies found with the larger basis sets are quite consistent. Cyclobutyne is calculated to be a transition state at most levels of theory, leading to cyclopropylidenecarbene. However, the latter does not have C^2^v symmetry, but rather undergoes a tilt of the carbene carbon toward a ring carbon leading to a distorted C^s structure. Perfluorocyclobutyne is calculated to have a significant activation energy for rearrangement at the MP2 level, but higher levels of theory suggest that it will rearrange spontaneously to perfluorocyclopropylidenecarbene, again with a distorted structure. The calculated heats of hydrogenation of the cyclobutynes are about 70 kcal/mol greater than for acetylene. The energies of a process by which perfluorocyclobutyne might be formed are also calculated.
Journal of the Chemical Society-Perkin Transactions 2
Ab Initio, carbenes, cyclobutyne, rearrangement
, Marquez, M.
and Gonzalez, C.
Rearrangement of Perfluorocyclobutyne, Journal of the Chemical Society-Perkin Transactions 2
(Accessed February 25, 2024)