The major product of the following reaction:

To find the final major product of this reaction sequence, let us break down what happens at each step.

The starting material is an aromatic compound containing two distinct hydroxyl groups: a phenolic OH directly attached to the benzene ring at the meta position, and an aliphatic primary alcohol group (OH) at the end of a three-carbon alkyl side chain. In the first step, treating the compound with chromium trioxide (CrO3), a strong oxidizing agent, selectively oxidizes the primary aliphatic alcohol at the end of the side chain into a carboxylic acid group (COOH), while leaving the phenolic OH group on the ring unaltered under these typical conditions. This turns the side chain into a 3-(3-hydroxyphenyl)propanoic acid derivative.

In the second step, the addition of thionyl chloride (SOCl2) along with heating converts the newly formed carboxylic acid group into a highly reactive acyl chloride group (COCl).

Finally, the third step involves heating, which triggers an intramolecular Friedel-Crafts acylation reaction. The phenolic OH group acts as a strong activating group, directing the electrophilic attack of the acyl chloride carbonyl carbon toward the benzene ring. Because the para position relative to the phenolic OH group is blocked by the alkyl side chain, the cyclization occurs exclusively at the ortho position relative to the OH group. The acyl chloride carbon attacks this ortho position, expelling a chloride ion as a leaving group and closing a new ring. Since the side chain contains three carbons, this intramolecular cyclization forms a stable six-membered cyclic ketone ring fused to the benzene ring. The final major compound is a bicyclic structured molecule containing a phenolic OH group on one ring and a ketone carbonyl group on the newly formed fused ring, specifically identified as a substituted alpha-tetralone derivative.