Carboxylic acids

All contain the -COOH functional group, e.g:

Physical properties

• Short chained acids are soluble in water (form hydrogen bonds with water). Solubility decreases as chain length increases.

• Melting and boiling points are higher than corresponding alkanes due to hydrogen bonds

• Must be in water to dissociate/ionise. Carboxylic acids are weak acids, e.g.

  • CH₃COOH(aq) ⇌ CH₃COO^- + H⁺

  • Carboxylate ion - relatively stable, delocalises the negative charge

  • Equilibrium constant still on the left

• The carbon that contains the functional group is carbon no. 1 when naming

Chemical reactions

React with;

• Metals → Salt+ hydrogen

• Alkalis/oxides → Salt + water

• Carbonates → Salt + water + CO₂

  • Test for carboxylic acids

  • E.g. ethanoic acid + calcium carbonate → calcium ethanoate + water + carbon dioxide

  • 2CH₃COOH + CaCO₃ → Ca(CH₃COO)₂ + H₂O + CO₂

• React with alcohols to form esters

• E.g.