Organic Synthesis

1) The hydroxide nucleophiles attacks at the electrophilic C of the ester C=O, breaking the pi bond and creating the tetrahedral intermediate.

2) The intermediate collapses, reforming the C=O results in the loss of the leaving group the alkoxide, RO^-, leading to the carboxylic acid.

3) An acid / base reaction. A very rapid equilibrium where the alkoxide,RO^- functions as a base deprotonating the carboxylic acid, RCO₂H, (an acidic work up would allow the carboxylic acid to be obtained from the reaction).