Due to the larger nuclear mass and smaller tunneling effects in the deuterium case, the CTST calculation with the standard scale factor performs slightly better than in the protium case, although the rate constant is still underestimated. The CVT/SCT calculations underestimate the rate. To explore the impact of SRP scale factors, we also conducted HDCPT2 calculations for the deuterated transition structures. However, the obtained SRP scale factors for the transition structure conformers are much larger than those in the case of CH 4 OH ‡ , resulting in SRP-scale-factor CVT/SCT results similar to standard-scale-factor CVT/SCT results. It is unclear why the SRP procedure is insufficient for good results in this case. Curiously, if we apply the SRP scale factors of CH 4 OH ‡ to CD 4 OH ‡ , the SRP CVT/SCT rate constants agree much better with experimental results; this is presumably due to cancellation of errors, but it does illustrate again the uncertainties that can be caused by anharmonicity.