Simplified Method of Ascertaining Steric Effects in Electrophilic Addition Reactions. A Comparison of Bromination, Oxymercuration, and Hydroboration

Article abstract of DOI:10.1021/ja00186a040

Correlations of ionization potentials (IP's) versus relative reactivities of a variety of alkenes toward bromination, oxymercuration, and hydroboration show very good (r=0.83) to excellent (r=0.98) agreement.The use of alkenes having a broad range of steric requirements and electronic effects reveals that bromination is independent of steric effects while oxymercuration and hydroboration each exhibit a natural separation into sterically similar groups, within which alkene IP's correlate with relative reactivities.In hydroboration of allylic compounds, characteristicsof the HOMO influence the regioselectivity as well as the relative reactivity.The data indicate that the transition states of the rate-determining steps of oxymercuration and hydroboration are similar, but both are different from that of bromination.