Rotational Mode Specificity in the F(–) + CH(3)I(v = 0, JK) S(N)2 and Proton-Transfer Reactions

[Image: see text] Quasiclassical trajectory computations are performed for the F(–) + CH(3)I(v = 0, JK) → I(–) + CH(3)F (S(N)2) and HF + CH(2)I(–) (proton-transfer) reactions considering initial rotational states characterized by J = {0, 2, 4, 6, 8, 12, and 16} and K = {0 and J} in the 1–30 kcal/mol collision energy (E(coll)) range. Tumbling rotation (K = 0) counteracts orientation effects, thereby hindering the S(N)2 reactivity by about 15% for J = 16 in the 1–15 kcal/mol E(coll) range and has a negligible effect on proton transfer. Spinning about the C–I bond (K = J), which is 21 times faster than tumbling, makes the reactions more direct, inhibiting the S(N)2 reactivity by 25% in some cases, whereas significantly enhancing the proton-transfer channel by a factor of 2 at E(coll) = 15 kcal/mol due to the fact that the spinning-induced centrifugal force hinders complex formation by breaking H-bonds and activates C–H bond cleavage, thereby promoting proton abstraction on the expense of substitution. At higher E(coll), as the reactions become more direct, the rotational effects are diminishing.