Alcohols

Alcohols

Primary alcohols (RCH₂OH) are oxidised by acidified $\mathrm{K_2Cr_2O_7}$ (orange → green) to aldehydes (distil off immediately) and then to carboxylic acids (heat under reflux). Secondary alcohols are oxidised to ketones. Tertiary alcohols are not oxidised (stays orange). Other reactions: combustion; dehydration with hot concentrated H₂SO₄ or Al₂O₃ → alkene; substitution with HX, PCl₅ or SOCl₂ → halogenoalkane; sodium → alkoxide + H₂; esterification with a carboxylic acid (conc. H₂SO₄ catalyst). The triiodomethane test (I₂ + NaOH, yellow precipitate) shows a $\mathrm{CH_3CH(OH)-}$ group.