Using molecular beam techniques we find that incident D atoms can abstract CD3 from a Cu(111) surface to yield CD4 in a direct (Eley-Rideal) gas-surface reaction with a cross section of similar to 10(-16) cm(2)/D atom. Dynamical evidence for a direct reaction includes the observation of an extremely sharp angular distribution that is clearly displaced from the surface normal, and the determination of a very : high translational energy of the product, E(f), which is similar to 2 eV. For a 0.25 eV D-atom beam incident at 45 degrees on a 95 K surface, this energy varies with the detection angle, theta(f), as E(f)(theta(f))=(1.8+theta(f)/45) eV, where theta(f)<0 degrees in the "backscattering" direction. For these conditions, the angular distribution approximately follows the function cos(70)(theta(f)-5.5), being peaked 5.5 degrees from the normal with a full width at half maximum of <17 degrees. Lowering the beam energy to 0.07 eV gives a broader angular distribution peaked at about 1.5 degrees from the normal, consistent with cos(60)(theta(f)-1.5). The reaction with 0.25 eV H incident at 45 degrees gives a similar distribution peaked at similar to 3.5 degrees from the normal. The shifts in the angular distributions are approximately consistent with parallel momentum conservation. The CD3/Cu(111) surface was prepared by thermal dissociation of CD3I on the surface or by adsorbing CD3 directly from a CD3 beam produced by the pyrolysis of azomethane.