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Revision: Alcohols, Phenols and Ethers Alcohols >> Alcohols Chemistry HSC Science (General) 12th Standard Board Exam Maharashtra State Board

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Definitions [1]

Definition: Esterification

Alcohols and phenols form esters by reaction with carboxylic acid, acid halides and acid anhydrides. This reaction is called esterification.

Key Points

Key Points: Chemical Properties of Alcohols and Phenols
  • Litmus Test — Aqueous alcohols are neutral to litmus, while aqueous phenols turn blue litmus red, confirming the acidic character of phenols.
  • Reaction with Bases — Phenols react with NaOH to form water-soluble sodium phenoxide (regenerated on acidification with HCl) but do not react with NaHCO₃, since phenol is a weak acid.
  • Esterification — Alcohols/phenols react with carboxylic acids (conc. H₂SO₄ catalyst), acid anhydrides (H⁺ catalyst), or acid chlorides (in pyridine) to form esters; Aspirin is the acetyl derivative of salicylic acid formed using acetic anhydride.
  • Reactivity with Hydrogen Halides — Order of alcohol reactivity: 3° > 2° > 1°; order of HX reactivity: HI > HBr > HCl (HCl needs anhydrous ZnCl₂ catalyst).
  • Oxidation of Alcohols — 1° alcohol → aldehyde (with PCC, best reagent) → further to carboxylic acid (with KMnO₄/K₂Cr₂O₇/HNO₃); 2° alcohol → ketone (with CrO₃); 3° alcohols resist oxidation and break C–C bonds only at high temperature.

Important Questions [36]

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