This is a retrosynthesis arrow. Provide cofrrect starting materials to make this product. == Ph Ph A. Ph (2 equiv.) B. Ph (2 equiv.) C. Ph (2 eqiv.) D. Ph (1 equiv
The Correct Answer and Explanation is:
✅ Correct Answer: A. PhCOCH₃ (2 equiv.)
Textbook-Style Explanation
The product shown is 1,3-diphenyl-1,3-propanedione, a β-diketone where two phenyl groups (Ph) are attached to each of the terminal carbonyl-containing carbons. The central carbon is methylene (CH₂), flanked by two carbonyls — a classic β-diketone motif. This type of compound is typically synthesized via a Claisen condensation, which is a base-catalyzed carbon–carbon bond-forming reaction between two esters or one ester and one ketone.
In this case, the reaction involves two equivalents of acetophenone (PhCOCH₃). Under basic conditions (commonly sodium ethoxide or sodium hydride in ethanol), one molecule of acetophenone is deprotonated at the α-carbon (next to the carbonyl group) to form an enolate ion. This enolate then performs a nucleophilic attack on the carbonyl carbon of a second acetophenone molecule, forming a β-keto intermediate.
After nucleophilic addition and proton transfer, the intermediate undergoes elimination of a leaving group (usually under heat), resulting in the β-diketone product, 1,3-diphenyl-1,3-propanedione.
The key feature of this mechanism is the formation of a new C–C bond between the α-carbon of one molecule and the carbonyl carbon of another. The phenyl groups remain untouched during the reaction and are retained in the product.
This transformation is highly efficient with symmetrical ketones like acetophenone, especially when both starting molecules are identical. Using 2 equivalents ensures both roles — enolate donor and carbonyl acceptor — are filled.
Other options (B, C, D) either include asymmetric ketones (which don’t lead to the symmetrical product) or incorrect stoichiometry (e.g., 1 equivalent in D).
Therefore, the correct starting material for this retrosynthesis is:
A. Acetophenone (PhCOCH₃), 2 equivalents
This classic Claisen condensation illustrates the utility of enolate chemistry in forming β-diketones, key intermediates in pharmaceuticals, ligands, and materials chemistry.
