10.1.8 Organic Families - Carboxylic Acids & Esters

Carboxylic acids

• Carboxylic acids is the name given to compounds containing the functional group carboxyl, -COOH
• The general formula of a carboxylic acid is C_nH_2n+1COOH which can be shortened to just RCOOH
  • (In some countries the family is  called alkanoic acid)

• The nomenclature of carboxylic acid follows the pattern alkan + oic acid
• There is no need to use numbers in the name as the carboxyl group will always be on the number 1 carbon atom

Carboxylic Acids Examples Table

Esters

• Esters are functional group isomers of carboxylic acids and contain the functional group, carboxylate, -COOR
• The general formula of an ester is usually represented as RCOOR where R can be the same or different on either side of the carboxylate group
• The nomenclature of esters follows the pattern alkyl + alkanoate
• The alkyl group in the name is the R group attached to the oxygen

Esters Examples Table

• Carboxylic acids and esters contain few similarities in their chemical and physical properties
• H-bonds are present between carboxylic acid molecules and not between esters, so this affects the melting point, boiling  point and solubility:
  • Smaller chain carboxylic acids are soluble in water and have higher boiling points than expected (e.g. ethanoic acid is 117 ^oC)
  • Esters are insoluble in water and have lower boiling points than their isomeric carboxylic acids ( e.g. methyl methanoate is 31 ^oC)