Extrapolating H‐atom transfer rate constants via thermochemical kinetics: The effect of tunneling

One of the important applications of chemical kinetics is the attempt to understand complex processes through kinetic modeling. This process frequently requires that rate constants be obtained by extrapolation of data either to higher or lower temperatures than the experimental, or by estimation or correlation with such data. Thermochemical kinetics combined with conventional transition state theory forms a framework from which this may be done. However, rate data for H transfer reactions may have a significant contribution from tunneling. In this work, a one dimensional approach to tunneling, consistent with conventional transition state theory, is taken to show how tunneling affects the extrapolation and correlation of rate constants in thermochemical kinetics. It is concluded that extrapolation and correlation are both quite good even when tunneling comprises 80% of the reaction. However, this is not without limitations, which are discussed.