⚗️ Alcohols & Ethers
Lucas test: tertiary = immediate cloudiness, secondary = slow, primary = no reaction
Lucas Test
Lucas reagent = ZnCl2 + HCl. Tertiary alcohols react immediately (cloudy). Secondary alcohols react slowly (5 min). Primary alcohols — no reaction at room temp. Used to distinguish alcohol classes.
⚗️ Alcohols & Ethers
PCC = stops at aldehyde, KMnO4/K2Cr2O7 = goes to carboxylic acid
Oxidation of Alcohols
Primary alcohols: PCC/PDC → aldehyde (stops). KMnO4 or K2Cr2O7 → carboxylic acid. Secondary alcohols → ketone with any oxidant. Tertiary alcohols — cannot be oxidized (no H on OH carbon).
⚗️ Alcohols & Ethers
'Ethers are relatively unreactive — only cleave with HI or HBr'
Ether Reactivity
Ethers are resistant to most reagents — no reaction with bases, mild acids, oxidants, or reducing agents. Cleaved only by concentrated HI or HBr at high temperature via SN2 or SN1.
⚗️ Alcohols & Ethers
Williamson Ether Synthesis: RO⁻ + R'X → ROR'
Williamson Synthesis
Best method to make ethers. Alkoxide (RO⁻) attacks alkyl halide via SN2. Use primary alkyl halide to avoid elimination. NaH converts alcohol to alkoxide first.
⚗️ Alcohols & Ethers
H-bonding in alcohols: higher BP than ethers of same MW
Alcohol vs Ether Properties
Alcohols have OH — can H-bond with each other → high boiling points. Ethers have no OH — cannot H-bond with each other → much lower boiling points. Both dissolve in water via H-bonding.