C3H4:: Density functional study of interconversion of isomers

The B3LYP density functional has been used to calculate the reaction paths for the interconversion of the three stable isomers of C3H4, namely, propyne, allene, and cyclopropene, and the results compared with experimental data. It is found that the trans nonplanar isomer of vinylmethylene plays a central role in the interconversions. Other thermochemical parameters, like the entropies of reaction and activation, have also been calculated. The rate constants of the various competing reactions have been calculated using the Rice-Ramsperger-Kassel-Marcus theory. Kinetic isotope effects for the reactions have also been investigated to gain an insight into their mechanisms. (C) 2003 Wiley Periodicals, Inc.