हिंदी

Preparation of Alcohols and Phenols

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Estimated time: 3 minutes
Maharashtra State Board: Class 12

Key Points: Preparation of Alcohols and Phenols

  • Hydroboration–Oxidation — This method of preparing alcohols from alkenes follows Anti-Markovnikov's rule; though the product seems as Markovnikov's, it is equivalent to anti-Markovnikov's addition.
  • Lucas Reagent Test — On adding Lucas reagent: a primary alcohol turns turbid only on heating, a secondary alcohol turns turbid slowly without heating, and a tertiary alcohol turns turbid immediately without heating.
  • Grignard Reagent Preparation of Alcohols — Formaldehyde (HCHO) + RMgX → 1° alcohol (R–CH₂OH); aldehyde (R'CHO) + RMgX → 2° alcohol; ketone (R'COR'') + RMgX → 3° alcohol.
  • Preparation of Phenol — Phenol can be prepared from chlorobenzene (NaOH/623 K/150 atm – Dow Process), benzene sulphonic acid (NaOH/573 K), cumene (O₂/cobalt naphthenate/423 K – commercial method), and aniline (NaNO₂–HCl/273 K, then H₂O/Δ – diazotisation).
  • Acidic Character — In aqueous medium, phenols show a weak acidic character, while alcohols are neutral.
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