Ab initio calculations of the thermolysis reaction of β-hydroxyalkynes in the gas phase

Thermolysis of three β-hydroxyacetylenes were studied with the second-order Møller–Plesset perturbation theory using a split valence polarization 6-31G(d) basis set. The obtained optimized geometries, atomic charge distributions and energy values are in agreement with the experimental measurements. The rate coefficients, calculated theoretically over the temperature range of 500–700K, are given by the Arrhenius equation: for the primary, logk1(s−1)=12.5–175.6kJmol−1(2.303RT)−1; for the secondary, logk2(s−1)=11.7–171.0kJmol−1(2.303RT)−1; and for the tertiary, logk3(s−1)=12.5–172.7kJmol−1(2.303RT)−1. The values of logA, from 11.7 to 12.5 (ΔS≠<0), indicate that these decompositions are concerted processes with a six-membered cyclic transition state.