Fischer Esterification (acid-catalyzed): RCOOH + R'OH ⇌ RCOOR' + H2O (H+ catalyst, reversible)

• Mechanism: Protonation of C=O → nucleophilic addition of R'OH → proton transfers → loss of H2O → deprotonation → ester
• Driven to completion by excess alcohol or removal of water

Saponification (base hydrolysis of ester): RCOOR' + NaOH → RCOONa + R'OH (irreversible — salt formation drives equilibrium)

• Mechanism: OH- attacks carbonyl C → tetrahedral intermediate → loss of OR' → carboxylate

Acid hydrolysis of ester: RCOOR' + H2O/H+ → RCOOH + R'OH (reversible, reverse of Fischer)