Indane-1,2,3-trione (the anhydrous form of ninhydrin) contains three keto groups, as shown in the structure below. Which of the labelled keto groups is expected to undergo hydration most easily?

Step-by-step solution

In indane-1,2,3-trione, there are three adjacent keto groups. The reactivity of a carbonyl group towards nucleophilic addition (like hydration) depends on the magnitude of the positive charge (electrophilicity) on the carbonyl carbon. The carbonyl carbon at position 2 is flanked by two highly electron-withdrawing carbonyl groups at positions 1 and 3. Due to the strong -I (inductive) effect of these adjacent carbonyl groups, the carbon at position 2 becomes highly electron-deficient and thus highly electrophilic. On