Carboxylic Acid

• What are carboxylic acids?

  • compounds that all contain the functional group 'COOH-'
  • form homologous series
• What is the 'COOH-' group?


  • consists of carbon atoms that formed a double bond with a lone oxygen atom.
  • A single bond with an oxygen atom in an OH- group

  
• Ending of a carboxylic acids ;

  'oic acids'
• First 4 carboxylic acids

  • methanoic acids
  • ethanoic acids
  • propanoic acids
  • butanoic acids
• Representing carboxylic acids

  • must show the COOH- functional group
• Identifying carboxylic acids

  • look out for the -COOH groups
  • 'anoic' acid ending
• Properties of carboxylic acids

  1. Reacts like other acids.

  Carboxylic acids + carbonates --> carbon dioxide + salt and water

  2. Dissolve in water / water-soluble and release H+ ions

  3. Weak acids = only partially ionise in water
• Carboxylic acids V Strong acids


  • Carboxylic acids have a higher pH (less acidic) than aqueous solutions of strong acids (sulphuric acid)
  • in the same CONCENTRATION
• Esters

  • Have a functional group -COO-
• How are esters formed?

  formed when alcohol + carboxylic acids --> ester + (water)
• Conditions needed for an ester to form

  • Presence of a strong acid catalyst
• Describe the formation of an ester

  • Carboxylic acids react with alcohols in the presence of an acid catalyst to produce pleasant-smelling compounds called esters.
• Ester


  • pleasant-smelling, fruity organic compounds
• Ethyl ethanoate

  ethanol + ethanoic acid --> ethyl ethanoate + water

  • in the presence of an acid catalyst
• Limewater

  • calcium hydroxide solution Ca(Oh)2
  • Forms calcium carbonate, CaCO3 when reacts with water + carbon dioxide
• Carboxylic acid + X carbonate

  • forms a salt, -anoate
  • carbon dioxide
  • water
• Esters

  • function group -COO-
  • homologous
• How are Esters formed?

  • alcohol + carboxylic acid
• Conditions needed for Esters to form

  • presence of strong, concentrated acid catalyst
• Reaction with alcohol and carboxylic acid

  • alcohol + carboxylic acid --> ester + water
  • in the presence of a strong, concentrated acid catalyst
• Example of Ethanol producing an Ester

  • Ethanol + ethanoic acid --> ethyl ethanoate + water
• How to classify oxidising agent?

  X[O]
• General formula of a Carboxylic Acid

  • C(n-1)H(2n+1)COOH

  Where n = -1
• Properties of carboxylic acids

  • Boiling point increases with increased carbon chain length.
  • Viscosity increases with increased carbon chain length.
  • Solubility in water decreases with increased carbon chain length.
• Why are carboxylic acids weaker than stronger acids such as Hydrochloric acid?

  • Carboxylic acids partially ionise in water / aqueous solution and does not fully dissociate it hydrogen ions.
• What property makes Esters appropriate solvents?

  • pleasant/sweet-smelling, fruity smells
  • used in perfumes
• Why are carboxylic acids also classified as a weak acids?

  • sometimes a reversible reaction
  • does not fully dissociate its hydrogen ions
• Uses of esters


  • Flavourings
  • Perfumes
  • Solvents
  • Plastic
• How to test between a carboxylic acid and an alcohol in a solution?

  Add an acid-base indicator

  • if carboxylic acid present, indicator will turn yellow-orange

  Add a hydrogen carbonate

  • if carboxylic acid present, will produce efferservence, indication of carbon dioxide