16.1.2—Describe

Alcohols burn in oxygen to form CO₂ and H₂O when combustion is complete. Their –OH group can be replaced to form a halogenoalkane, and sodium removes the acidic O–H hydrogen to form an alkoxide and H₂.

Use the reagent to identify the reaction: HX or a phosphorus/ thionyl chloride reagent gives substitution, while sodium gives an acid–metal reaction. The carbon skeleton usually remains unchanged.

2ROH + 2Na → 2RONa + H₂. Ethanol + PCl₅ → chloroethane + POCl₃ + HCl, illustrating conversion of –OH into a leaving group.

Alcohols are weak acids, not hydroxide salts, and sodium reacts at the O–H bond rather than replacing the whole carbon chain.