Which of the following forms an enol to the greatest extent ? (a) (b) (c) (d)

Here, the compound in the third option is a 2,4-dione compound. Aldehydes and Ketones 3 Here, the stability of the enol formed is higher due to resonance compared to the other keto forms. Also, due to possibility of intra-molecular hydrogen bonding, extra stability is obtained in this structure hence will prefer enol form more than the keto form. Therefore, the correct answer is option (c) Preparation of Aldehydes & Ketones