2.7 - Alcohols and Carboxylic Acids

• What is the functional group of alcohols?

  Hydroxyl/ -OH group
• What is the general formula for alcohols?

  Cn H2n+1 OH
• What are the conditions for the industrial production of ethanol from ethene? (Hydration to go from alkene to alcohol)

  • Steam
  • Phosphoric acid (aq)
  • 300 degrees celsius
  • High pressure
• How can ethanol be produced from a renewable source?

  Ethanol can be produced from the fermentation of sugars
• How can alcohols be produced from alkenes?

  • Fermentation
  • Industrial hydration
• What conditions are needed for the fermentation of sugars to form ethanol?

  • Yeast
  • 30-40 degrees celsius
  • Anaerobic conditions
• Why is the production of ethanol from sugars said to be 'carbon neutral'?

  Ethanol when used as a fuel released carbon dioxide, which will be taken in by crops during photosynthesis. This balances out the carbon dioxide that is released when the ethanol is burned.
• Why might someone arue that the production of ethanol from fermentation of sugars is no carbon-neutral?

  Energy is required to power the harvesting, transportation, etc. of the crops and ethanol. This energy will come from the burning of fuel, releasing carbon dioxide.
• What is formed when alcohols undergo dehydration?

  Alkenes and a water molecule
• What are the conditions for dehydrating an alcohol?

  Either

  • heat with a strong acid catalyst (sulfuric acid)
  • pass vapour over an aluminium oxide catalyst
• How are alcohols classified?

  Alcohols are classified based on the number of carbon atoms bonded to the carbon atom that bears the hydroxyl group.
• Primary alcohols...

  one R group is bonded to the carbon with a hydroxyl group on it
• Secondary alcohols...

  two R groups are bonded to the carbon with a hydroxyl group on it
• Tertiary alcohols...

  three R groups are bonded to the carbon with a hydroxyl group on it
• What are primary alcohols oxidised to form?

  Aldehydes
• How are primary alcohols oxidised to aldehydes?

  Heat the primary alcohol with acidified potassium dichromate and distill - when completed the potassium dichromate will turn from orange to green
• How are primary alcohols oxidised to form carboxylic acids?

  Heat the primary alcohol under reflux with acidified potassium dichromate - when completed the potassium dichromate will turn from orange to green
• What are secondary alcohols oxidised to form?

  Ketones
• How are secondary alcohols oxidised to form ketones?

  If a secondary alcohol is heated under reflux with acidified potassium dichromate, it will form a ketone - when complete the acidified potassium dichromate will turn from orange to green
• What qualitative test can be carried out for the identification of primary and secondary alcohols?

  Add acidified potassium dichromate - if either alcohol is present it will turn from orange to green
• What test can be carried out to identify carboxylic acids?

  Add sodium hydrogencarbonate (NaHCO3) - fizzing will be observed as carbon dioxide is released. The carbon dioxide can be tested for with limewater
• What is produced when carboxylic acids react with bases?

  A salt and water
• What is produced when carboxylic acids react with carbonates?

  A salt, carbon dioxide, and water
• What is produced when carboxylic acids react with hydrogencarbonates?

  A salt, carbon dioxide and water
• How do alcohols react with carboxylic acids?

  Alcohol and carboxylic acids react to form esters, in a process called esterification.
• What are the reaction conditions for esterification?

  • Heat
  • Sulfuric acid catalyst
• When naming esters, what suffix is used?

  -anoate
• Explain how ethanol can be separated from water:

  Ethanol and water have different boiling points and so distillation is a suitable technique