Ester formation [RCO2(–)]
Ester formation (RCO2‾) Definition:
Alkyl halides (or tosylates) will react with carboxylate ion to form esters in SN2 reaction.
Ester formation (RCO2‾) Explained:
This is a one-step transformation. The nucleophile (acetate) attacks alkyl halide (methyl bromide), with a simultaneous expulsion of the leaving group (bromide). This is a concerted process because bond making takes place at the same time as a bond breaking.
In the transition state, the negative charge on the nucleophile has spread partly onto the leaving group. As the reaction comes to completion, the leaving group evolves to a fully charged anion.