Answer:
4-hydroxybutanoic acid + H⁺ ⇒ γ-butyrolactone + H₂O
Step-by-step explanation:
The simplest route to prepare γ-butyrolactone is the intramolecular reaction of an alcohol with an acid. The required starting material is 4-hydroxybutanoic acid (γ-hydroxybutyric acid). See attachment for the condensed reaction mechanism. The H⁺ acts as a catalyst.