Properties and uses of monohydric alcohols

Lower alcohols (methanol, ethanol, propanols) are liquids with a characteristic smell, and from about C₁₂ they are solids. Their boiling points are much higher than those of the corresponding hydrocarbons (ethanol 78 °C, ethane −89 °C) because the –OH groups form hydrogen bonds between molecules. Chemical properties: (1) with active metals they give an alkoxide and hydrogen: 2C₂H₅OH + 2Na → 2C₂H₅ONa + H₂↑; (2) with carboxylic acids in the presence of sulfuric acid they form esters (esterification): C₂H₅OH + CH₃COOH ⇌ CH₃COOC₂H₅ + H₂O; (3) dehydration: above 140 °C within the molecule (alkene): C₂H₅OH → C₂H₄ + H₂O, below 140 °C between molecules (ether): 2C₂H₅OH → C₂H₅–O–C₂H₅ + H₂O; (4) with HBr –OH is replaced by a halogen: C₂H₅OH + HBr → C₂H₅Br + H₂O; (5) in oxidation a primary alcohol becomes an aldehyde and then an acid, a secondary alcohol becomes a ketone, and a tertiary alcohol resists oxidation; (6) combustion: C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O. Ethanol is a solvent, a disinfectant and a fuel additive; methanol is extremely poisonous: even a small amount can cause blindness or death. Ethanol harms the nervous system and the liver and is absolutely unsuitable for teenagers.