Why does this matter? Because most of organic synthesis happens in basic or neutral conditions. This makes the acetal the perfect .
Imagine you are building a complex drug molecule. You have a ketone that you need to keep intact, but your next reaction involves a Grignard reagent (a strong nucleophile and base). If you add the Grignard to the molecule with a free ketone, you’ll get an unwanted alcohol—the reaction will fail. acetally