Alcohols Flashcards
What is the equation for a dehydration reaction
Alcohol —> Alkene + water
What is used as a catalyst in the alcohol dehydration reaction
Concentrated H2SO4 and concentrated H3PO4
Describe ethanol production via hydration of ethene
React an alkene with steam and an acid catalyst
What are the conditions for ethanol production via hydration of ethene
300 degrees Celsius, 60 atm, H3PO4 catalyst
Why isnt ethanol production by hydration of ethene preferable
- ethene is a finite resource
- drilling for crude oil is an expensive process and damages the environment
How else can ethanol be produced
Fermentation of glucose
Is the reaction of fermentation of glucose a exo or endothermic reaction
Exothermic reaction
Give 3 conditions for the fermentation of glucose
- yeast
- anaerobic
- 30 - 40 degrees Celsius
Why is ethanol production by fermentation of glucose preferable
Uses cheap equipment and renewable resources
Give the overall equation for fermentation of glucose
C6 H12 O6 —> 2 C2 H5 OH + 2 CO2
How is ethanol separated in the fermentation of glucose
Via fractional distillation
Define a biofuel
A fuel which is made from dead organic matter
Give an example of a biofuel
Ethanol when made from fermentation of glucose
Give 2 advantaged of biofuels
- they’re renewable energy sources
- they’re carbon neutral
Why are biofuels carbon neutral
CO2 released when burnt = CO2 absorbed during photosynthesis
Give 2 disadvantages of biofuels
- cars must be modified to use ethanol fuel
- land needed to grow crops
Why isn’t ethanol production by fermentation of glucose completely carbon neutral
Fuels burnt to transport crops, and power machines for fertilisers
Give the equation for photosynthesis
6CO2 + 6H2O —> C6 H12 O6 + 6O2
Give the equation for burning ethanol
2 C2 H5 OH + 5O2 —> 4CO2 + 6H2O
What oxidising agent is used to oxidise and alcohol
Acidified potassium dichromate
What is observed when an alcohol is oxidised
Orange Cr2 O7 - reduces to green Cr3+
How do you acidify potassium dichromate solution
Add dilute sulfuric acid
What do primary alcohols oxidise to
Distillation: oxidise to aldehydes
Reflux: oxidise to carboxylic acids
What do secondary alcohols oxidise to
Ketones under reflux
What conditions are needed to oxidise a primary alcohol to an aldehyde
Limited amount of dichromate. Warm gently with distillation
What conditions are needed to oxidise a primary alcohol to a carboxylic acid
Excess of dichromate, heat under reflux
What do tertiary alcohols oxidise to
They don’t oxidise
Why is fermentation done in the absence of air
Presence of air can cause extra reactions to occur, like the oxidation of ethanol to ethanoic acid
Give 3 disadvantages of producing ethanol by fermentation
- slow batch process of high production costs
- not pure ethanol produces=d, so has to be purified by fractional distillation
- depletes land used for growing crops
Give 3 advantages of producing ethanol by hydration of ethene
- faster reaction
- continuous process
- purer product
Give 3 disadvantages of producing ethanol by hydration of ethene
- High technology equipment needed
- Ethene is non renewable
- High energy costs for pumping to produce high pressures
