Carboxylic acids

• Carboxylic acids


  Compounds which contain a -COOH group
• Carboxylic acids


  • Compounds where the -COOH group is attached either to a hydrogen atom or to an alkyl group
• Naming carboxylic acids


  The name counts the total number of carbon atoms in the longest chain - including the one in the -COOH group. If you have side groups attached to the chain, you always count from the carbon atom in the -COOH group as being number 1.
• Salts of carboxylic acids

  When carboxylic acids form salts, the hydrogen in the -COOH group is lost and replaced by a metal
• Salts of carboxylic acids

  • Sodium ethanoate
• Ionic bond in salts of carboxylic acids


  The bond between the sodium and the ethanoate is ionic. Don't draw a line between the two (implying a covalent bond).
• Naming salts of carboxylic acids

  Although the name is written with the sodium first, the formula is always written with the carboxylate group first
• Physical properties of carboxylic acids

  • Governed by their ability to form hydrogen bonds
• Hydrogen bonding in pure carboxylic acids

  Carboxylic acids can form dimers through hydrogen bonding, which increases the size of the molecule and the van der Waals dispersion forces
• Solubility of carboxylic acids in water

  Carboxylic acids with up to four carbon atoms are soluble in water due to hydrogen bonding with water molecules. Larger carboxylic acids are less soluble due to the hydrocarbon "tails" disrupting hydrogen bonding.
• Making carboxylic acids by oxidising primary alcohols or aldehydes


  Primary alcohol oxidised to aldehyde, then aldehyde oxidised further to carboxylic acid
• Nitriles


  Compounds which contain -CN attached to a hydrocarbon group
• Nitriles


  • Ethanenitrile, Propanenitrile, 2-Methylpropanenitrile
• Formation of nitriles


  Reaction between halogenoalkanes and cyanide ions, or reaction between aldehydes/ketones and hydrogen cyanide
• Converting nitriles to carboxylic acids

  Acid hydrolysis: Heat nitrile with dilute acid to form carboxylic acid

  Alkaline hydrolysis: Heat nitrile with alkali to form carboxylate salt, then add acid to liberate carboxylic acid