EFFETS POLAIRES DANS LES REACTIONS DE TRANSFERT HOMOLYTIQUE INTRAMOLECULAIRE D'HYDROGENE

Article abstract of DOI:10.1016/0040-4020(82)80022-7

In this paper we analyse the influence of a phenyl substituent on the relative rates of the 1-5 and 1-6 intramolecular hydrogen transfers.Compared to the abstraction of an aliphatic H atom, the activation energy for the abstraction of a benzylic H atom is smaller.The effect is nevertheless more important with a primary alkyl radical (1,3 kcal/mole) than with an alkoxy radical (0,9 kcal/mole).This can be analysed in terms of a polar effect.In addition, the size of the effect is too small to make a short distance transfer of a H atom feasible; this is in keeping with the statement that H atom migration requires a linear transition state.