Alcohols & Carboxylic Acids

9.26C Recall the formulae of molecules of the alcohols, methanol, ethanol, propanol (propan-1-ol only) and butanol (butan-1-ol only), and draw the structures of these molecules, showing all covalent bonds
  • Alcohols contain the functional group –OH
  • The first 3 members of the series are methanol, ethanol and propanol.

Methanol, ethanol and propanol
  • They are used as fuels and solvents, and ethanol is the main alcohol in alcoholic drinks.
9.27C Recall that the functional group in alcohols is –OH

*see 9.26C

9.28C Core Practical: Investigate the temperature rise produced in a known mass of water by the combustion of the alcohols ethanol, propanol, butanol, and pentanol
9.29C Recall the formulae of molecules of the carboxylic acids, methanoic, ethanoic, propanoic and butanoic acids, and draw the structures of these molecules, showing all covalent bonds

  • Ethanoic acid is a member of the carboxylic acids, they have the functional group –COOH.
  • First four members are: methanoic acid, ethanoic acid, propanoic acid and butanoic acid
  • Dissolve in water to produce acidic solutions
  • React with carbonates to produce carbon dioxide
  • React with ethanol in the presence of an acid catalyst to produce esters
  • They do not ionise completely, so do not release many H+ ions, so it is a weak acid. (HT only)
  • This means they have a higher pH (weak acid) than solutions of strong acids of the same concentration.
  • React with alcohols to produce esters…

  • They have the functional group –COO-.
  • Only ester to know is ethyl ethanoate : ethanol + ethanoic acid -> ethyl ethanoate + water
9.30C Recall that the functional group in carboxylic acids is –COOH

*see 9.29C

9.31C Recall that ethanol can be oxidized to produce ethanoic acid and extend this to other alcohols (reagents not required)
  • Ethanol can be oxidised to form ethanoic acid.
  • It can be oxidised by chemical oxidising agents or microbial action.
  • Vinegar is an aqueous solution which contains ethanoic acid.
9.32C Recall members of a given homologous series have similar reactions because their molecules contain the same functional group and use this to predict the products of other members of these series
 9.33C Describe the production of ethanol by fermentation of carbohydrates in aqueous solution, using yeast to provide enzymes
  • Ethanol can be produced by fermentation with yeast, using renewable sources.

SUGAR -> CARBON DIOXIDE + ETHANOL

9.34C Explain how to obtain a concentrated solution of ethanol by fractional distillation of the fermentation mixture
  • Ethanol concentration is about 15% from fermentation, ethanol is separated from the reaction mixture using fractional distillation
    • 1 water and ethanol solution are heated
    • 2 ethanol evaporates first, cools, then condenses
    • 3 water left evaporates, cools, the condenses