Polar Addition and Elimination Reactions

Abstract

Addition and elimination processes are the reverse of one another. In general, the two processes follow a similar mechanistic path in opposite directions, the final state of the system depending on the conditions. For example, hydration of alkenes and dehydration of alcohols are both familiar reactions that constitute a related addition-elimination pair: Open image in new window In these circumstances, mechanistic conclusions about the addition reaction are applicable to the elimination reaction and vice versa. The principle of microscopic reversibility states that the mechanism (pathway) traversed in a reversible reaction is the same for the reverse reaction as for the forward one under the same conditions. Thus, if an addition-elimination system proceeds by a reversible mechanism, the intermediates and transition states involved in the addition process are the same as in the elimination reaction.