The major product of the following reaction is:

Concept:

The reaction involves hydrolysis or nucleophilic substitution in first step followed by oxidation and dehydration in last step. The most important fact is that, the Br group attached directly to aromatic ring will not undergo substitution.

Hydrolysis is defined as (hydro-, meaning 'water', and lysis, meaning 'to unbind') is any chemical reaction in which a molecule of water ruptures one or more chemical bonds.

The term is used broadly for substitution, elimination, and fragmentation reactions in which water is the nucleophile.

Nucleophilic substitutions a fundamental class of reactions in which an electron rich nucleophile selectively bonds with or attacks the positive or partially positive charge of an atom or a group of atoms to replace a leaving group the positive or partially positive atom is referred to as an electrophile.

The whole molecular entity of which the electrophile and the leaving group are part is usually called the substrate. The nucleophile essentially attempts to replace the leaving group as the primary substituent in the reaction itself, as a part of another molecule

From the given reaction the aryl halide remains unaffected and the directly attached Br group undergo substitution process then it react in the presence of chromium trioxide and hydrogen the nucleophilic substitution takes place.