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 H-2*S(D-2*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 (BuSH)-S-1 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.