Which statement correctly differentiates aldol condensations from Claisen condensations in terms of substrates and products?

• A. Aldol uses aldehydes/ketones to give β-hydroxy carbonyls; Claisen uses esters to give β-keto esters
• B. Aldol uses esters to give β-keto esters; Claisen uses aldehydes/ketones to give β-hydroxy carbonyls
• C. Aldol forms alcohols; Claisen forms alkenes
• D. Claisen uses aldehydes/ketones to give β-hydroxy carbonyls; Aldol uses esters to give β-keto esters

Answer: (A)

Aldol condensation and Claisen condensation are distinguished by the type of starting materials and the products they form. In an aldol condensation, aldehydes or ketones are the partners. An enolate of one carbonyl attacks the carbonyl of another molecule, yielding a β-hydroxy carbonyl compound (the aldol). Under the right conditions, this intermediate often loses water to give an α,β-unsaturated carbonyl compound. In contrast, Claisen condensation uses esters as substrates. The enolate of one ester attacks the carbonyl carbon of another ester, forming a β-keto ester after expelling an alkoxide leaving group. So the correct statement is that aldols involve aldehydes/ketones producing β-hydroxy carbonyls, while Claisen condensations involve esters producing β-keto esters. The other options mix up substrates or products and don’t reflect these distinct outcomes.