Addition-Elimination Reactions Explained

If SN1 and SN2 don’t work… addition–elimination takes over. Addition–elimination reactions are most

common in acyl derivatives like acid chlorides, anhydrides, esters, and amides.

Step one: a nucleophile adds to the electrophilic carbonyl carbon. This breaks the π bond and forms

a tetrahedral intermediate. Next, the tetrahedral intermediate collapses, reforming the carbonyl

and eliminating a leaving group. Key rule: the better the leaving group, the faster the reaction.

If you see: - a carbonyl - a nucleophile - a decent leaving group

→ think addition–elimination, not SN1 or SN2.