To understand the different QMT reactivities of 1 and 2, we conducted a detailed analysis of their intrinsic reaction coordinates (IRC) for the QMT pathways using the UB3LYP/6-31G(d) level of theory (Figure ), according to Kozuch et al. Concurrently, we employed CVT/SCT to compute the half-lives (τ) for these reactions at the same level of theory, which enabled us to quantitatively assess the likelihood of QMT occurring under our experimental conditions. For the 1 → 4 C-H bond insertion reaction, the computed half-life of 20 h agrees well with the experimental value. At UB3LYP/6-31G(d) the reaction leading towards anti-Bredt adamantene (10) gives a computed half-life of > 9 x 10 22 h, indicating that this reaction is not competitive (Figure ); indeed, 10 was not detectable in our experiments. This also implies that ICS cannot be studied with 1.