Identify the appropriate reagent required to carry out the following transformation:

Step-by-step solution

The given reaction shows the conversion of a ketone (acetophenone) into a cyclic ketal. The formation of a cyclic ketal with a five-membered ring requires the reaction of the carbonyl compound with a 1,2-diol. Observing the structure of the product, the ketal part consists of a - O - CH ₂- CH ₂- O - group attached to the original carbonyl carbon. This indicates that the reagent used is ethylene glycol, HOCH ₂ CH ₂ OH . The reaction takes place in the presence of a catalytic acid, and water is removed to drive the e