Carboxylic acids

• The carboxylic acids form a homologous series. Like all homologous series, the carboxylic acids:

  • have the same general formula

  • differ by CH2 in molecular formulae from neighbouring compounds

  • show a gradual variation in physical properties, such as their boiling points

  • have similar chemical properties

Functional group

• The functional group in the carboxylic acids is the carboxyl group, –COOH

• It is responsible for the typical reactions of carboxylic acids, which are weak acids.

  • Vinegar is a dilute solution of ethanoic acid.

General formula

• The general formula for the carboxylic acids is CnH2n+1COOH (where n is the number of carbon atoms in the molecule, minus 1).

• Remember that the O atoms are not joined to each other

Acid properties

• The carboxylic acids have the typical properties of acids. For example, they:

  • dissolve in water to form acidic solutions with pH values lower than 7

  • react with metals to form a salt and hydrogen

  • react with bases to form a salt and water

  • react with carbonates to form a salt, water and carbon dioxide

• These properties are due to the –COOH functional group.