Alcohols, Phenols and Ethers

• Introduction & Classification

  • Alcohols ($\text{R-OH}$)
    • Monohydric, Dihydric, Trihydric, Polyhydric
    • Classification by $\text{C-OH}$ bond type: $1^\circ$, $2^\circ$, $3^\circ$
  • Phenols ($\text{Ar-OH}$)
    • Monohydric, Dihydric, Trihydric
  • Ethers ($\text{R-O-R'}$)
    • Simple (Symmetrical) vs Mixed (Unsymmetrical)

• Nomenclature

  • IUPAC System
    • Alcohols: Alkane $\rightarrow$ Alkanol
    • Phenols: Derivative of Benzene (Phenol)
    • Ethers: Alkoxyalkane

• Preparation of Alcohols

  • From Alkenes
    • Acid-catalyzed hydration (Follows Markovnikov's rule)
    • Hydroboration-oxidation (Anti-Markovnikov product)
  • From Carbonyl Compounds
    • Reduction of aldehydes and ketones ($\text{LiAlH}_4$, $\text{NaBH}_4$, $\text{H}_2/\text{Ni}$)
    • Reduction of carboxylic acids and esters
  • From Grignard Reagents ($\text{RMgX}$)
    • Formaldehyde $\rightarrow$ $1^\circ$ Alcohol
    • Other Aldehydes $\rightarrow$ $2^\circ$ Alcohol
    • Ketones $\rightarrow$ $3^\circ$ Alcohol

• Preparation of Phenols

  • From Haloarenes (Dow's Process)
  • From Benzenesulphonic acid
  • From Diazonium salts (Hydrolysis)
  • From Cumene (Industrial method, yields Acetone as byproduct)

• Physical Properties

  • Boiling Points
    • High due to Intermolecular Hydrogen Bonding
    • Decreases with branching
  • Solubility
    • Soluble in water due to H-bonding (decreases with higher alkyl chain)

• Chemical Reactions of Alcohols

  • Reactions Involving Cleavage of $\text{O-H}$ Bond
    • Acidity of alcohols (Reaction with active metals like $\text{Na}$, $\text{K}$)
    • Esterification ($\text{Alcohol} + \text{Carboxylic Acid} \rightleftharpoons \text{Ester}$)
  • Reactions Involving Cleavage of $\text{C-O}$ Bond
    • Reaction with Lucas Reagent ($\text{HCl} + \text{ZnCl}_2$) to distinguish $1^\circ, 2^\circ, 3^\circ$ alcohols
    • Reaction with $\text{HX}$, $\text{PCl}_3$, $\text{PCl}_5$, $\text{SOCl}_2$
  • Oxidation Reactions
    • Primary alcohol $\rightarrow$ Aldehyde $\rightarrow$ Carboxylic acid
    • Secondary alcohol $\rightarrow$ Ketone
    • Dehydrogenation using Copper catalyst at $573\text{ K}$

• Chemical Reactions of Phenols

  • Nature: More acidic than alcohols due to resonance stabilization of phenoxide ion
  • Electrophilic Aromatic Substitution
    • Halogenation (with $\text{Br}_2$/water $\rightarrow$ 2,4,6-tribromophenol)
    • Nitration (with dilute $\text{HNO}_3 \rightarrow$ ortho/para nitrophenol)
    • Kolbe's Reaction (Formation of Salicylic acid using $\text{CO}_2$)
    • Reimer-Tiemann Reaction (Formation of Salicylaldehyde using $\text{CHCl}_3$ + $\text{NaOH}$)
  • Special Reactions
    • Reaction with Zinc dust ($\rightarrow$ Benzene)
    • Oxidation with $\text{Na}_2\text{Cr}_2\text{O}_7$ ($\rightarrow$ Benzoquinone)

• Ethers

  • Preparation
    • Williamson Ether Synthesis ($\text{R-X} + \text{R'-ONa} \rightarrow \text{R-O-R'} + \text{NaX}$)
    • Dehydration of alcohols (acid-catalyzed at $413\text{ K}$)
  • Physical Properties
    • Miscibility with water (comparable to amines/ethers)
    • Lower boiling points than isomeric alcohols
  • Chemical Reactions
    • Cleavage of $\text{C-O}$ bond with $\text{HI}$ (Forms alkyl iodide + alcohol/phenol)
    • Electrophilic substitution in aromatic ethers (Anisole)
      • Halogenation, Friedel-Crafts alkylation and acylation