Definitions [1]
Alcohols and phenols form esters by reaction with carboxylic acid, acid halides and acid anhydrides. This reaction is called esterification.
Key Points
- 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.
Methanol (Wood Spirit):
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Produced by catalytic hydrogenation of CO:
\[\ce{CO + 2H2 ->[ZnO/Cr2O3, 200-300atm, 573-673K] CH3OH}\]
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Highly poisonous; used as a solvent in paints and varnishes.
Ethanol:
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Produced by fermentation of sugar:
\[\ce{C12H22O11 + H2O ->[Invertase] \underset{Glucose}{C6H12O6} + \underset{Fructose}{C6H12O6}}\]
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Used as a solvent and in the preparation of carbon compounds.
Differentiation between Methanol & Ethanol:
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Iodoform test: Ethanol gives yellow ppt (CHI₃); methanol gives no reaction.
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With salicylic acid + H₂SO₄: Methanol forms methyl salicylate (characteristic odour); ethanol gives no specific odour.
Important Questions [17]
- Write chemical reactions to prepare ethanamine from: Acetonitrile
- Identify a and B Respectively in the Following Reaction: Tert-butyl Alcohol ->20‰H2so4363k a + H2o ->Hbrh2o2 B
- How are the following compounds prepared
- Identify the Compound 'B' in the Following Series of Reaction
- Which of the Following Reagents is Best for the Following Conversion?
- How is Ethanol Prepared from Methanal by Using Grignard Reagent?
- Which Among the Following Reducing Agents is Not Used to Reduce Acetaldehyde to Ethyl Alcohol?
- Write chemical reactions to prepare ethanamine from: Nitroethane
- How Will You Prepare Ethanol, Propan-2-ol and 2-methylpropan-2-ol from Grignard’S Reagent?
- How Are the Following Compounds Prepared? Propan-1-ol from Propanal
- Propene on Oxidation with Diborane in Presence of Alkaline Hydrogen Peroxide Gives
- Convert the following: acetaldehyde to isopropyl alcohol.
- The Compound D is
- Which of the Following is the First Oxidation Product of Secondary Alcohol?
- Write the reactions involved in dehydration of 1°, 2° and 3° alcohols.
- Write Resonance Structures of Aniline. What is the Action of Benzene Diazonium Chloride on Ethanol?
- Write chemical reactions of following reagents on methoxyethane: dilute H2SO4
