3.3.5 Alcohols
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Industrial production of alcohols - hydration (5)
Hydration of alkenes using steam (reversible) 300°C 60 atm Solid phosphoric acid catalyst Low reaction yield (5%) so unreacted ethene gas is recycled
Industrial production of alcohols - fermentation (5)
Fermentation of glucose 30-40°C Yeast in anaerobic conditions At 15% alcohol, yeast dies so distillation is used to increase concentration Purification step takes extra time and money
Hydration of alkenes - advantages (3)
Very fast Pure product Low labour costs
Hydration of alkenes - disadvantages (2)
Uses oil - finite resource Expensive equipment needed
Fermentation of glucose - advantages (2)
Renewable resource - sugars Cheap equipment
Fermentation of glucose - disadvantages (3)
Very slow Impure product so needs further processing High labour costs
What is biofuel?
A fuel made from recently dead biological material
What are the advantages of biofuels? (3)
Renewable energy sources More sustainable Considered to be carbon neutral
What are the disadvantages of using biofuels? (3)
Land used for fuel cannot be used to grow food Deforestation Fertilisers can pollute waterways
Why is the statement ‘ethanol is a carbon-neutral fuel’ not valid? (5)
When plants are burned the same amount of CO2 is released as they took in in the first place: Photosynthesis: 6CO2 + 6H2O > C6H12O6 + 6O2 Fermentation: C6H12O6 > 2C2H5OH + 2CO2 Combustion: 2C2H5OH + 6O2 > 4CO2 + 6H2O However, energy is used by machinery in the processing and transportation of biofuels, releasing more carbon dioxide so ethanol is not carbon neutral
How are aldehydes produced from alcohols? (3)
Primary alcohol oxidised to aldehyde Heated potassium dichromate and sulphuric acid Distillation apparatus
How are carboxylic acids produced from alcohols? (3)
Primary alcohol oxidised to carboxylic acid Potassium dichromate and sulphuric acid Reflux apparatus
How are ketones produced from alcohols? (3)
Secondary alcohol oxidised to ketone Acidified potassium dichromate Reflux
How are tertiary alcohols distinguished from other alcohols? (2)
They are not oxidised when reacted with potassium dichromate Solution remains orange
How are alkenes formed from alcohols? (2)
Elimination (dehydration) Heated with conc. sulphuric acid catalyst
Why is it beneficial to produce alkenes by dehydration?
It provides a source of monomers for addition polymerisation that are not derived from crude oil