Computational study of bystander effects in the 1,2-H shifts of alkylmethylcarbenes

Bystander substituent effects in the 1,2-H shifts of several singlet alkylmethylcarbenes (CH₂Y-C-CH₃) have been studied using density functional theory. Bystander effects similar to that of alkylchlorocarbenes were observed. The methyl, halo, and phenyl groups accelerate 1,2-H shifts in the order Ph > F > Me > Cl, Br > H. Singlet/triplet energy separation of these carbenes have also been examined. All studied carbenes have singlet ground states, and the ability of Y groups to stabilize the relative energies of singlet states is F > Cl > Br> Ph > Me > H. (C) 2000 Elsevier Science B.V.