Alcohols

• Alcohols can be dehydrated to form alkenes
• alkenes can be hydrated to form alcohols
• alcohols undergo elimination reactions with a concentrated acid catalyst to produce alkenes
• alkenes can be heated with steam in the presence of an acid catalyst to produce alcohols
• Hydroxyls have two lone pairs of electrons
• Hydrating an alkene is the standard industrial method for producing alcohols
• Conditions for fermentation

  • yeast
  • 30-40 degrees
  • anaerobic conditions
• Hydration of an alkene produces a pure alcohol whereas fermentation is very impure
• Fermentation is more sustainable than hydrating alkenes as glucose is a renewable resource whereas alkenes come from crude oil
• biofuels are fuels made from biological material
• biofuels are considered carbon neutral as they release the same amount of carbon dioxide as the plant took in when it was growing
• disadvantages of biofuels

  • land cannot be used to grow crops
  • deforestation to make land
  • fertilisers can pollute water
• primary alcohols are oxidised to aldehydes, then to carboxylic acids
• secondary alcohols are oxidised to ketones
• tertiay alcohols are not oxidised
• aldehydes and ketones are carbonyl compunds as they contain the functional group C=O
• the notation [O] represents an oxidising agent
• primary alcohols are gently oxidised by distillation to form aldehydes
• primary alcohols are vigorously oxidised by reflux to form carboxylic acids
• to form carboxylic acids the primary alcohol has to by heated with excess oxidising agent
• heating under reflux means the temperature can be increased to boiling without losing volatile solvents, reactants or products
• secondary alcohols are oxidised by reflux in acidic conditions to form ketones
• Fehling’s solution and Benedict’s solution

  aldehyde = brick red

  ketone = stays blue
• Tollens‘ solutions

  aldehyde = silver mirror

  ketone = clear
• The oxidising agent used to oxidise alcohols is acidified potassium dichromate
• Acidified potassium dichromate changes from orange to green when an alcohol is oxidised