Alcohols

• What is the general formula for alcohols?

  C$n$H$2n+$$1$OH
• When is the prefix hydroxy used in organic compounds?

  When another functional group is present
• Why is the C-O-H angle in alcohols 105 degrees?

  Lone pairs repel more than bonding electrons
• Does hydrogen bonding occur between alcohol molecules?

  Yes
• Why are short-chain alcohols soluble in water?

  Hydrogen bonding predominates over non-polar bonding
• How is ethanol made industrially?

  By reacting ethene with steam
• What are the advantages and disadvantages of fermentation for ethanol production?

  Advantages:

  • Considered 'green'
  • Renewable resource

  
  

  Disadvantages:

  • Slow at low temperatures
  • Enzymes die at high temperatures
• What are the conditions for fermentation?

  • Temperature: 37C
  • Slightly acidic
  • Anaerobic conditions
• What can primary alcohols be oxidized to?

  Aldehydes, then carboxylic acids
• What can secondary alcohols be oxidized to?


  Ketones
• What are the conditions to oxidize a primary alcohol to an aldehyde?

  Dilute acid and less potassium dichromate
• What color change indicates the oxidation of a primary alcohol to an aldehyde?

  Orange to green
• What are the conditions to oxidize an aldehyde to a ketone?

  Concentrated sulfuric acid and excess potassium dichromate
• Where is the oxygen located in an aldehyde molecule?

  At the end of the molecule
• How can we test between aldehydes and ketones?

  • Tollens Silver Mirror Test:
  • Ag+ ions reduced to metallic silver
  • Aldehyde oxidized, no reaction with ketone
  • Fehling's Test:
  • Blue copper (II) ions oxidize aldehydes
  • Forms a brick-red precipitate
• How do we produce ethanol industrially?

  React ethene with steam with a phosphoric acid catalyst
• What happens in fermentation?

  • Plants anaerobically respire
  • Produces ethanol and carbon dioxide
• Why is air kept out of fermentation vessels?

  Prevent oxidation of alcohol to ethanoic acid
• What happens once we obtain alcohol from anaerobic respiration?

  Obtain alcohol from solution by fractional distillation
• What is eliminated in elimination reactions with alcohol?

  A water molecule
• Give the three equations in the use of alcohol produced by fermentation to prove it is carbon neutral.

  • 6H2O + 6CO2 -> C6H12O6 + 6O2 (photosynthesis)
  • C6H12O6 -> 2C2H5OH + 2CO2 (anaerobic respiration)
  • 2C2H5OH + 6O2 -> 4CO2 + 6H2O (combustion)
  • 6 molecules of CO2 absorbed, 6 molecules of CO2 released
• Why is fermentation of alcohol not really a carbon neutral process?


  Transportation of materials
• Define biofuel


  A fuel derived from living matter
• What are the conditions for the dehydration of alcohols?

  • Excess hot concentrated sulfuric acid
  • Heated aluminium oxide
• What are the conditions for converting a primary alcohol to aldehyde?

  Dilute acid and less acidified potassium dichromate
• What are the conditions for converting an alcohol to carboxylic acid?

  • Concentrated sulfuric acid
  • Excess potassium dichromate
  • Reflux
• What are secondary alcohols oxidised to? Byproduct?

  Ketones

  Water
• How do we represent oxygen in the oxidation of alcohols to carboxylic acids?

  2[O]
• Why are short chain alcohols able to interact with water?

  OH group interacts with H group
• Why do longer chain hydrocarbons not interact with water?


  Hydrocarbon chain predominates