Alcohols

• Ethanol popular for 10,000 years
• Strictly ethanol; methanol = blindness

Nomenclature

• Alcohols have formula $ROH$; -OH referred to as hydroxyl group
• IUPAC naming: replace -e with -ol
  • If highest priority, carbon has lowest number possible
• Naming branches: start with alcohol
• Alkyl group as derivative, followed by alcohol (e.g., ethyl alcohol, isobutyl alcohol)
• If not highest priority group: substituent as hydroxy-
• Alcohol with aromatic ring = phenol
  • OH group partially acidic

    

• Benzene ring with 2 substituents:
  • Ortho = adjacent
  • Meta = 1 carbon between
  • Para = opposite sides

Physical properties

• Can H bond → high melting and boiling points (longer chain = more London dispersion forces → higher BP)
• More than one OH group → more bonding
• O atom pulls e⁻ density away from H → generates partial positive charge
• Hydroxyl hydrogens of phenols more acidic than other alcohols → phenols form salts with inorganic bases like NaOH
• E⁻ withdrawing substituents → increase acidity
• E⁻ donating groups → decrease acidity
• More alkyl groups → less acidic (donate e⁻, destabilize negative charge, stabilize positive charge)

Oxidation reactions

• Primary alcohols → aldehydes via pyridinium chlorochromate (PCC)
  • Stops at aldehyde because PCC lacks water
• Aldehydes hydrate to geminal diols (1,1-diols) → can oxidize to carboxylic acids
• PCC converts -OH → =O
• Secondary alcohols → ketones via PCC or other oxidizing agents
• Tertiary alcohols cannot oxidize without breaking C-C bond
• Strong oxidizing agents (Chromium VI) → carboxylic acids
  • Chromium VI reduced to Chromium III
  • Examples: CrO₃, Jones oxidation (primary alcohol → carboxylic acid, secondary → ketone)

Mesylates and Tosylates

• Hydroxyl groups protonated → better leaving groups
• Mesylate: -SO₃CH₃
  • Prepared using methyl sulfonyl chloride + alcohol + base

  

• Tosylate: -SO₃C₆H₄CH₃
  • From p-toluenesulfonyl chloride
  • Structure: Benzene - S(=O)₂ - O-R

  

• Can protect groups to prevent alcohol from reacting

Protecting Groups

• Alcohols protect other functional groups
• Aldehydes/ketones + 2 eq alcohol/diol → acetals (primary C-OR)₂ or ketals (secondary C-OR)₂
• Acetals/ketals do not react with LAH
• Deprotection: revert to carbonyl using aqueous acid

Quinones and Hydroxyquinones

• Phenols + oxidizing agents → quinones
  • Resonance stabilized electrophiles
  • Not aromatic, conjugated ring structure
  • Serve as e⁻ acceptors
  • (benzoquinone)

  

• Vitamin K1 (phylloquinone) important for photosynthesis, clotting factor carboxylation
• Hydroxyquinones: further oxidized quinones
  • Same ring & carbonyl backbone, more hydroxyl groups
  • Slightly less electrophilic
  • Number of hydroxyl groups indicated by prefix or hydroxy-

  

Ubiquinone

• Coenzyme Q, vital e⁻ carrier
• Most oxidized form; reduced to ubiquinol upon e⁻ acceptance
• Conjugated rings stabilize molecule during e⁻ transport
• Lipid-soluble due to alkyl chain
• Functions similarly to NADH, FADH₂, and NADPH