Identify the final major product [S] obtained in the following sequence of reactions: (i) LiAlH₄ , (ii) H₃O^+ [ P ] [ ] conc. H₂SO₄ [ Q ] (i) B₂H₆ /THF, (ii) H₂O₂/OH^- [ R ] PCC [ S ]

Step-by-step solution

The starting material is acetophenone ( C₆H₅-CO-CH₃ ). Reaction with LiAlH₄ followed by acidic workup reduces the ketone to a secondary alcohol. Thus, [P] is 1-phenylethanol ( C₆H₅-CH(OH)-CH₃ ). Heating [P] with concentrated H₂SO₄ causes dehydration, forming an alkene. The major product is styrene ( C₆H₅-CH=CH₂ ) due to conjugation with the benzene ring. Thus, [Q] is styrene. Hydroboration-oxidation of [Q] using B₂H₆ /THF followed by H₂O₂/OH^- leads to anti-Markovnikov hydration of the alkene. This yields a primary