Alcohols Flashcards
what are the two methods in which ethanol can be produced
- the fermentation of glucose
- the direct hydration of ethene
what are the conditions for the fermentation of glucose
- yeast catalyst (enzymes)
- 37°C
- absence of O₂
what are the advantages of the fermentation of glucose
- low energy input
- uses sugar cane which is renewable
- it is said to be carbon neutral
what are the disadvantages of the fermentation of glucose
- low yield
- impure product ( further distillation is required )
- slow rate of reaction
- environmental issues due to deforestation and loss of habitats
why is the fermentation of glucose technically ‘carbon neutral’
- the CO₂ released when it is burnt is balanced by the CO₂ taken in by the source plant during photosynthesis
equations:
photosynthesis - 6H₂O + 6CO₂ → C₆H₁₂O₆ + 6O₂
fermentation - C₆H₁₂O₆ → 2CH₃CH₂OH + 2CO₂
combustion - 2CH₃CH₂OH + 6O₂ → 4CO₂ + 6H₂O
what are the conditions for the direct hydration of ethene
- steam
- heat
- concentrated H₂SO₄ catalyst
what are the advantages of the direct hydration of ethene
- high yield of purity
- fast rate of reaction
- its a continuous process
what are the disadvantages of the direct hydration of ethene
- high energy input needed
- ethene is obtained from crude oil which is non-renewable
what reagent is used to oxidise an alcohol
- acidified potassium dichromate (IV)
- K₂Cr₂O₇/H⁺
what is observed when an alcohol is oxidised
- colour change from orange to green
what do primary alcohols turn into when oxidised
- aldehyde then carboxylic acid
what do secondary alcohols turn into when oxidised
- ketone
what condition is needed for the oxidation of an alcohol to an aldehyde or ketone
- distillation
what condition is needed for the oxidation of an alcohol to a carboxylic acid
- reflux
- excess acidified potassium dichromate
how to test between primary, secondary alcohols and tertiary alcohols
- add potassium dichromate
- colour change orange to green confirms it is a primary or secondary alcohol
