Lecture Notes: Alcohol, Phenol, and Ether

Differentiation and Nomenclature

• Alcohol: Hydrocarbon (R) with H replaced by OH group.
• Phenol: Benzene ring with H replaced by OH group.
• Ether: Confusion often with esters, generally R-O-R' structure.

Classification of Alcohols

• Based on the number of OH groups:
  • Monohydric: One OH group
  • Dihydric: Two OH groups
  • Trihydric: Three OH groups
  • Polyhydric: Four or more OH groups

Important Question Types (PYQs)

• Questions based on hybridization (sp3, sp2, etc.)
• Concept of allylic alcohols: OH attached to a carbon next to a double-bonded carbon.

General Nomenclature Rules

• Word Root: Number of carbon atoms (meth, eth, prop, but, etc.).
• Primary Suffix: Type of bond (single, double, triple - an, en, yn).
• Secondary Suffix: Functional group (e.g., -ol for alcohols).
• Prefix:
  • Primary Prefix: Position, compulsory modifiers.
  • Secondary Prefix: Additional groups, side chains.

Hybridization and Structure-based Questions

• SP3 Hybridized Carbons and SP2 Hybridized Carbons: Importance and typical bond angles.
• Example: Alcohols are generally classified based on the SP3 hybridization of carbon attached to OH.

Structural Functional Groups

• Bond angles in alcohols, phenols, and ethers.
  • Alcohol Bond Angle: Typically around 108.5°
  • Phenol Bond Angle: Around 109° due to repulsion.
  • Ether Bond Angle: Around 111° due to bulky R groups causing repulsion.

Methods of Preparation

Alcohols

• Nucleophilic Substitution: Using alkyl halides (R-X) treated with aqueous KOH.
• Hydration of Alkenes:
  • Acid-Catalyzed Hydration: Direct addition of H2O.
  • Hydroboration-Oxidation: BH3 followed by H2O2.
  • Oxymercuration-Demercuration: Addition of Hg(OAc)2, followed by NaBH4.
• Reduction of Carbonyl Compounds:
  • Aldehydes and Ketones: Reduction using NaBH4 or LiAlH4.
  • Carboxylic Acids: Reduction using LiAlH4.
• Grignard Reagent: Reaction of RMgX with aldehydes/ketones to form alcohols.

Phenols

• Haloarenes: Reaction with NaOH.
• Benzene Sulfonic Acid: Reaction with NaOH to form phenoxide ion.
• Salicylic Acid: Conversion route.
• Cumene Process: Formation of phenol and acetone.

Ethers

• Williamson Synthesis: Reaction of alkoxide ion (R-O) with alkyl halide (R'-X).

Physical Properties

• Boiling Points:
  • Impact of molecular mass and branching.
  • Order: Carboxylic acids > Alcohols > Aldehydes > Ketones > Ethers > Hydrocarbons.
• Solubility:
  • Low molecular mass alcohols are soluble in water due to hydrogen bonding.
  • Solubility decreases with increased carbon chain length.

Chemical Properties

Alcohols

• Acidity:
  • Alcohols as weak acids but less acidic than water.
  • Factors affecting acidity: Presence of electron-donating or withdrawing groups (Inductive effect).
• Reactions:
  • Esterification: Formation of ester with acids.
  • Reaction with Sodium Metal: Formation of alkoxide and H2 gas.
  • Dehydration: Formation of alkenes using conc. H2SO4 based on temperature.
  • Oxidation: Forming aldehydes, ketones, or carboxylic acids based on the reagent used.

Phenols

• Reactions with Metals: Formation of phenoxide ion.
• Electrophilic Substitution Reactions:
  • Dilute HNO3: Formation of ortho and para nitrophenols.
  • Concentrated HNO3: Formation of 2,4,6-trinitrophenol (picric acid).
  • Bromination: Formation of multiple brominated products.
  • Sulfonation: Formation of ortho and para sulfonic acids.
  • Friedel-Crafts Alkylation and Acylation: Formation of alkylated or acylated phenols.
• Kolbe Reaction: Formation of salicylic acid from phenoxide ion and CO2.
• Riemer-Tiemann Reaction: Formation of salicylic aldehyde using CHCl3.

Important Reactions and Examples

• Grignard Reagent Reaction: Conversion to alcohol using formaldehyde.
• Benzyl Chloride to Benzyl Alcohol: Nucleophilic substitution using NaOH.
• Mechanisms:
  • Dehydration of Ethanol: Formation of ethene via protonation and carbocation steps.

Summary of Key Topics

• Reimer-Tiemann Reaction
• Williamson Synthesis
• Acidity of Alcohols
• All Phenol Reactions

Next Steps

• Proceed to Aldehydes, Ketones, and Carboxylic Acids after a break.