The C-D bond in CD4 is slightly stronger than C-H bond in CH4 , thus (delta) H for abstraction of D is slightly greater than for H. The abstraction being the slow step, the removal of H will be faster.
Chemically, H and D are identical but (C-D) bonds; therefore the energy of activation of D is greater than that of H. Since abstraction is a slow step, removal of H will be faster.
Relative abstraction of H:D = 2.7:1
Relative abstraction of 4H:D = 10.8:1
= 11 : 1
