In the reaction mechanism for isopentyl acetate formation, which reactant provides the arrow-indicated oxygen?

In the reaction mechanism for the formation of isopentyl acetate through an esterification reaction, isopentyl alcohol acts as the nucleophile that attacks the carbonyl carbon of acetic acid. This results in the formation of a tetrahedral intermediate, where the hydroxyl group from isopentyl alcohol contributes its oxygen atom to the new ester bond during the reaction.

The process involves the transfer of the hydroxyl group from isopentyl alcohol to the carbonyl carbon of acetic acid. Therefore, when considering which reactant provides the arrow-indicated oxygen in the mechanism, isopentyl alcohol is the correct choice as it contributes its oxygen atom to the final ester product, isopentyl acetate. This is essential to understand because the nature of nucleophiles and how they interact in organic reactions is a key concept in reaction mechanisms.