alcohols and carboxylic acids

• alcohols contain the functional group -OH, the first four members of this series are methanol (CH3OH), ethanol (CH3CH2OH), propanol (CH3CH2CH2OH), butanol (CH3CH2CH2CH2OH)
• CORE PRACTICAL pt.1

  1. use a stand, boss and clamp to secure a steel or copper can over a spirit burner. Adjust the height of the can so that the lid of the burner can be removed and replaced safely
  2. measure and record the mass of a spirit burner with its lid
  3. use a measuring cylinder to add 100 cm3 of cold water to the can
  4. measure and record its temperature
• CORE PRACTICAL pt.2

  1. place the spirit burner underneath the can. Remove the lid and light the wick
  2. stir the water carefully with the thermometer. When the temperature has increased by about 20C, replace the lid to put the flame out
  3. measure and record the mass of the spirit burner with its lid, and the maximum temperature of the water
  4. repeat steps 2 to 6 with different alcohols, starting with fresh water each time.
• CORE PRACTICAL

  you should find that the temperature is raised more as the chain length of the alcohols increases, because the combustion of longer chain alcohols releases more energy
• carboxylic acids contain the functional group -COOH, the first four members of this group are methanoic acid (CHOOH), ethanoic acid (CH3COOH), propanoic acid (CH3CH2COOH) , butanoic acid (CH3CH2CH2COOH)
• any alcohol can be oxidised to produce a carboxylic acid e.g. ethanol can be oxidised to produce ethanoic acid,
• members of a given homologous series have similar reactions because their molecules contain the same functional group, this helps us predict the products of other members of the series
• ethanol can be produced by fermentation with yeast, using renewable sources

  • it is produced from carbohydrates (can be sugars from fruit or starch)
  • the mixture must be kept warm and under anaerobic conditions (warm- so reaction is fast enough but yeast doesn’t denature anaerobic- only carbon dioxide and water would be produced if not)

  glucose -> ethanol + carbon dioxide
• concentrated solution of ethanol by fractional distillation of fermentation mixture

  • water and ethanol solution are heated
  • ethanol evaporates first (has a lower boiling point than water), cools, then condenses
  • water left evaporates, cools, then condenses