In the given reaction sequence, identify the major product (B).

Step-by-step solution

The starting material is 1,2-dihydronaphthalene. Ozonolysis of 1,2-dihydronaphthalene with O₃ followed by reductive workup with Zn/H₂O cleaves the alkene double bond. This yields a molecule with both an aromatic aldehyde and an aliphatic aldehyde. The intermediate product (A) is 2-(3-oxopropyl)benzaldehyde. Treatment of compound (A) with a base ( OH^- ) initiates an intramolecular aldol condensation. The base abstracts an -proton from the - CH ₂- CH ₂- CHO chain (from the CH ₂ adjacent to the aliphatic carbonyl) to