Overview of Alcohols, Phenols, and Ethers

Feb 9, 2025

Lecture Notes on Alcohols, Phenols, Thiols, and Ethers

Introduction

  • Focus on alcohols, phenols, thiols, and ethers
  • Key topics: reactions, naming, classification

Alcohols

Structure

  • Organic compounds with hydroxyl group (OH)
  • General formula: R-OH
  • Carbonyl carbon: carbon attached to OH

Classification

  • Primary alcohol: carbonyl carbon attached to one carbon
  • Secondary alcohol: carbonyl carbon attached to two carbons
  • Tertiary alcohol: carbonyl carbon attached to three carbons

Physical Properties

  • Similar structure to water, polar
  • Capable of hydrogen bonding
  • High boiling points due to hydrogen bonding
  • Solubility: Alcohols (1-4 carbons) soluble in water
    • Solubility decreases with longer carbon chains
    • Increased OH groups increase solubility

Naming (IUPAC Rules)

  • Longest carbon chain with the OH group
  • Replace 'e' in alkane with 'ol'
  • Number chain to give OH lowest number
  • Cyclic alcohols: OH is carbon 1

Phenols

  • Hydroxyl group attached to benzene ring
  • Polar, slightly water-soluble
  • Used in healthcare as antiseptics and disinfectants

Ethers

Structure

  • General formula: R-O-R
  • Slightly polar due to C-O bond

Naming

  • Common names: Alphabetize alkyl groups + 'ether'
  • IUPAC names: Longest alkane chain + 'alkoxy'

Properties

  • Moderate chemical inertness, volatile, flammable
  • Medically used as anesthetics

Thiols

  • General formula: R-SH
  • Similar to alcohols but contains sulfur
  • Naming: suffix 'thiol', indicate position with a number

Properties

  • Strong odors (skunk, onions, garlic)

Reactions Involving Alcohols

Hydration

  • Alkene + water → Alcohol (with acid catalyst)

Hydrogenation

  • Aldehyde/Ketone + H2 → Alcohol (with catalyst)

Dehydration

  • Alcohol → Alkene + Water (with acid and heat)
  • Follows Saytzeff’s Rule

Oxidation

  • Primary alcohols: oxidize to aldehydes and further to carboxylic acids
  • Secondary alcohols: oxidize to ketones
  • Tertiary alcohols: do not oxidize

Notable Alcohols and Their Uses

  • Methanol: Toxic, used as solvent and fuel
  • Ethanol: Used in beverages, fuel
  • Isopropyl alcohol: Rubbing alcohol, disinfectant
  • Ethylene glycol: Antifreeze
  • Glycerol: Sweetener, used in cosmetics

Important Concepts

  • Intermolecular Forces: Hydrogen bonding in alcohols
  • Solubility: Affected by number of OH groups
  • Boiling Points: Higher due to hydrogen bonding

Key Reactions

  • Dehydration reverses hydration
  • Oxidation and Reduction: Oxidation involves loss of H, gain of O

Application in Biological Systems

  • Alcohol’s role in forming NADH+, a coenzyme

Note: Ensure to memorize classification, naming conventions, and key reactions for alcohols, as they are crucial for understanding subsequent chemical processes.

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