Alcohols

• How are ethers related to alcohols?

  They are functional group isomers.
• Why are alcohols more reactive than their corresponding alkanes?

  The oxygen is more electronegative so produces a polar bond.
• Why do alcohols have a higher boiling point than their corresponding alkanes?

  They can form hydrogen bonds with each other.
• Why are alcohols soluble?

  They form hydrogen bonds with water. This makes the first 3 alcohols soluble in water. After that, the long alkyl chain interferes with the hydrogen bonds.
• How are alcohols produced industrially?

  • The hydration of alkenes in the presence of an acid catalyst.
  • Fermentation of glucose
• Uses of ethanol:

  • A solvent
  • A chemical feedstock- used to make other chemicals
  • Alcoholic drinks
• What is the reagent in a hydration reaction of an alkene?

  Steam
• What are the conditions for a hydration reaction of an alkene?

  • $300^{\circ}c$
  • 60 atm
  • Concentrated phosphoric acid catalyst
• How ethanol is produced by fermentation:

  • Carbohydrates from crops broken into glucose.
  • Glucose converted to ethanol in anaerobic respiration.
  • Ethanol removed from mixture by fractional distillation.
• What are the reagents in the fermentation process?

  Glucose and yeast
• What are the conditions for fermentation?

  • Anaerobic
  • Aqueous
  • $30-40^{\circ}c$
• Equation for fermentation:

  $C_6H_{12}O_6\ \rightarrow\ 2CO_2+$$2CH_3CH_2OH$
• Why must fermentation be carried out in the absence of air?

  To prevent oxidation
• Why is a compromise temperature of 35 used for fermentation?

  To provide sufficient rate of reaction without denaturing the enzyme.
• When does fermentation stop?

  When the reaction mixture contains about 15% ethanol (fractional distillation can be used to separate the ethanol).
• What is the raw material used for the hydration of ethene?

  Crude oil (finite resource)
• What is the quality of the product from hydration of ethene?

  Pure
• What is the quality of the product from fermentation?

  Impure
• Which process in the production of alcohol has a fast rate of reaction?

  Hydration. (Fermentation is a slow process).
• Which process in the production of alcohol has high energy requirements?

  Hydration reactions. (Fermentation requires low energy)
• What type of process is the hydration of ethene?

  Continuous
• What type of process is fermentation?

  Batch
• What is the atom economy for the hydration of ethene?

  100%
• Which process for the production of alcohol is expensive?

  Hydration reactions (high set up cost but low labour cost).
• What is a biofuel?

  A fuel derived or produced from renewable biological sources. Biofuels are carbon-neutral.
• What is a carbon-neutral activity?

  One that has no net carbon emissions to the atmosphere.
• What are the disadvantages of using crops to produce fuel?

  • Land used to grow crops for fuel can not be used to grow food.
  • Fertilisers are added to soil to increase biofuel crop production.
  • Deforestation to create land for biofuel crops to grow.
• What is the main oxidising agent for alcohols?

  Acidified potassium dichromate (VI)
• What is used to acidify potassium dichromate?

  Sulphuric acid
• What colour change is observed when acidified potassium dichromate acts as an oxidising agent?

  Orange solution to green solution.
• Half equation for acidified potassium dichromate acting as an oxidising agent:

  $Cr_2O_7^{2-}+$$14H^+$$+$$6e^-\ \rightarrow\ 2Cr^{3+}+$$7H_2O$
• What are the possible oxidation products of a primary alcohol?

  • Aldehydes
  • Carboxylic acid
• What is the possible oxidation product for a secondary alcohol?

  Ketone
• What can be used to distinguish between secondary and tertiary alcohols?

  Acidified potassium dichromate
• How is acidified potassium dichromate used to distinguish between a secondary or tertiary alcohol?

  Tertiary alcohols are not oxidised so there will be no colour change (orange to green).
• A primary alcohol is oxidised initially to an aldehyde and then a carboxylic acid.
• When will an aldehyde be formed from a primary alcohol?

  If a primary alcohol is reacted with an equimolar amount of an oxidising agent.
• When is reflux used?

  When heating organic reaction mixtures for long periods.
• How does the condenser prevent organic vapours from escaping during reflux?

  Condensing them back to liquids.
• Why is the end of the condenser never sealed during reflux?

  The build up of gas pressure could cause the apparatus to explode.