Organic Chemistry: Alcohols and Phenols

Alcohols and Phenols

• Alcohols are organic compounds containing a hydroxyl (-OH) group attached to a carbon atom.
• Phenols are aromatic compounds containing a hydroxyl (-OH) group bonded directly to an aromatic ring.

Types of Alcohols

• Methanol (methyl alcohol)
• Ethanol (ethyl alcohol)
• 1-propanol (n-propyl alcohol)
• 2-propanol (isopropyl alcohol)
• 1-butanol (n-butyl alcohol)
• 2-butanol (sec-butyl alcohol)
• 2-methyl-1-propanol (isobutyl alcohol)
• 2-methyl-2-propanol (tert-butyl alcohol)
• 2-propen-1-ol (allyl alcohol)
• Cyclohexanol (cyclohexyl alcohol)
• Phenylmethanol (benzyl alcohol)

Types of Phenols

• Phenol
• p-chlorophenol
• 2,4,6-tribromophenol
• m-hydroxybenzoic acid
• p-hydroxybenzaldehyde
• p-nitrophenol
• 2,4-dinitrophenol

Physical Properties of Alcohols

• Boiling Point: Increases with increasing molecular weight due to stronger intermolecular forces
• Solubility: Low molecular weight alcohols are completely miscible with water due to hydrogen bonding; as the carbon chain lengthens, solubility decreases.
• Examples of boiling points and solubility of alcohols are listed in Table 7.1

Acidity of Alcohols and Phenols

• Alcohols are weakly acidic and phenols are more acidic because of resonance stabilization.

Reactions of Alcohols

• Reaction with sodium metal: Alcohols react with sodium metal to produce hydrogen gas and sodium alkoxide.
• Formation of alkyl halides: Alcohols react with halogen acids (HX) to form alkyl halides via SN1 or SN2 mechanisms
• Oxidation Primary alcohols can be oxidized to aldehydes and then to carboxylic acids; secondary alcohols are oxidized to ketones.
• Various oxidizing agents like K₂Cr₂O₇, H₂SO₄, CuO, Jones' reagent and PCC are used

Reactions of Phenols

• Reaction with nitric acid: Phenols react with dilute nitric acid to form nitrophenols, and with concentrated nitric acid to form trinitrophenol (picric acid).
• Reaction with Bromine: Phenol reacts with Bromine to form 2,4,6-tribromophenol

Thiols

• Similar to alcohols, but with a sulfur atom instead of an oxygen.