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 alkylm ethylcarbenes (CH2Y-C-CH3) have been studied using density functional theor y. 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 s tates is F > Cl > Br > Ph > Me > H. (C) 2000 Elsevier Science B.V. All righ ts reserved.