The conformational isomerization of propiolic acid and its H/D isotopic counterparts are studied by using high-level quantum chemistry in conjugation with semiclassical transition state theory and second order vibrational perturbation theory. The electronic structure calculations were carried at DFT and MP2 levels of theory. The vibrational anharmonicity coefficients including the fully coupled vibrational modes of the reaction coordinate of the transition state, used in semiclassical transition state theory, are computed at hybrid functional B3LYP in conjugation with aug-cc-pVTZ and SNSD basis sets. The corresponding solutions give rate as well as the equilibrium constants between the isomers and the isotopic analogs. (C) 2016 Elsevier B.V. All rights reserved.