Kinetic Isotope Effect in Hydrogen Isotope Exchange Between Hydrogen Sulphide or Thiol and Alcohol in Gas and Solution

The kinetic parameters of the tritium exchange between H2 * S(D2 * S) or MeSH*(MeSD*) and MeOH(MeOD) vapours on PTFE and glass surface were measured. The *HH/*DD kinetic isotope effects are significantly lower than those for the reaction of phosphines with methanol. The kinetics of deuterium exchange between ButSH and EtOD in solutions of C6D12 and CD3CN had been studied and HH/DD isotope effect was evaluated. It appeared to be smaller than that in the vapours. These results suggest that contrary to the exchange reactions in phosphine, the elementary reaction of HH-transfer in four center transition state is not the rate limiting step and H-bond formation as well as diffusion controlled processes should be taken into account.