The rate of the reaction between H and DCN

It has been suggested that the slightly endothermic reaction between H and DCN to produce HCN and D serves to deplete DCN in hot core regions of giant molecular clouds. We have calculated the rate of this reaction for a range of temperatures up to 500 K with a combination of ab initio quantum chemical and dynamical techniques. We find that the reaction has two potential barriers lying between the reactants and products. These barriers permit only a very slow reaction except at high temperatures. We calculate that the rate coefficient k of the reaction follows the formula k (cm3 s−1) = 2 10−11Γtexp(−4931/T ), where Γt is a tunneling correction. The estimated rate coefficient at 300 K is 5 10−18 cm3 s−1; this rate coefficient is far too small to be important in the destruction of DCN.