Chapter 7- Alcohols

Alcohols- commercially important Ethanol CH 3 CH 2 OH - Produced by fermentation or hydration of ethylene CH 2 =CH 2 + H 2 O H 2 SO 4 CH 3 -CH 2 OH Commercial EtOH 95% H 2 O 5% Can’t purify further by distillation To remove water Absolute alcohol use CaO CaO + H 2 OCa(OH) 2 Ethanol- Solvent, fuel, antiseptic, reagent

Covalent OH bond ~ 480 kJ mol -1 Hydrogen bond ~ kJ mol -1 Much weaker but has important effects (i)Boiling points of alcohols are higher than would be predicted based on molecular weight -Extra energy required to break the intermolecular hydrogen bonds (ii) Lower molecular weight alcohols are soluble in water CH 3 CH 2 OH CH 3 OCH 3 CH 3 CH 2 CH 3 MW B.P o C -24 o C -42 o C

Preparation of Alcohols (i) Reduction of aldehydes, ketones, carboxylic acid derivatives (ii) Addition of H 2 O to an alkene e.g. oxymercuration

Intermolecular Hydrogen Bonding

Alcohols are weak acids

7.8 Dehydration of alcohols- alkenes - Occurs by heating with a strong acid

Mechanism of dehydration

7.9 Reaction of Alcohols with Hydrogen Halides

Thiols: S (sulfur) analogues of alcohols