The study of isotope effects of chloroform and chloromethane using vibrational frequencies

In this work, the effect of isotopes on vibrational frequencies of chloroform and chloromethane has been studied using different computational quantum chemistry methods. It was found that for our calculations, the results of the B3LYP method are comparable or even better than the more expensive MP2 method. By scaling the computed vibrational frequencies, it is possible to obtain the isotope effects very similar to the experimental data. The obtained results in this work show that it is possible to use a simple procedure to find a transition structure and to calculate vibrational frequencies, then study the kinetic isotope effects for the environmentally important processes. In this work, the reduced isotopic partition function ratios and the equilibrium constants for isotope exchange of chloroform and chloromethane has been calculated.