Challenge of the Traditional Olefin Electrophilic Addition Reaction Mechanism Induced by Different Substituents
Chloronium ion is an important intermediate in the traditional electrophilic addition reaction between olefins and hypochlorite,and it is the only reaction mechanism taught in class regarding the olefin electrophilic addition reaction.However,quantum chemistry calculation results indicate that different substituents of olefins cause the changes of the electrophilic addition reaction mechanism.Ethylene substituted with general electron donating groups(EDGs)and weak electron withdrawing groups(EWGs)reacts with HOCl via the traditionally believed chloronium ion intermediate to generate Markovnikov products,in which carbon-cation intermediate yields for substituents being EDGs featuring p-π or π-π conjugation with the C=C moiety of olefin.When the substituents are moderate and strong EWGs,the olefins prefer the Anti-Markovnikov products through the concerted and the new nucleophilic addition reaction mechanisms,respectively.Therefore,it is very necessary to pay attention to the applicable system of the mechanism rather than the traditional chloronium ion intermediate mechanism,when teaching the mechanism of olefin electrophilic addition.
electrophilic addition reactionreaction mechanismchloronium ion
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