Alcohols and carboxylic acids Flashcards
What are alcohols?
A homologous series containing -OH as the functional group.
How can ethanol be made?
Through reacting with steam or fermentation.
What are the conditions for the industrial preparation of ethanol?
300C, 60-70 atm and a catalyst of phosphoric acid.
What is fermentation?
An enzyme-catalysed reaction that converts sugars to ethanol.
How can ethanol be separated from the products in fermentation?
It can be separated from the aqueous mixture using fractional distillation as it has a boiling temperature of 80C.
Give an example of a fermentation reaction
C6H12O6 (glucose) —> 2C2H5OH + 2CO2
What are biofuels?
Fuels that have been produced using a biological source.
How is bioethanol obtained?
By the fermentation of sugars in plants and biodiesel from the oils and fats present in the seeds of some plants.
What are some advantages of biofuels?
- Renewable- The plants needed can be grown each year and animal waste can also be used
- Greenhouse gas- Although they produce CO2 when burnt, the plants have taken in CO2 for photosynthesis, making the use of biofuels carbon neutral.
- Economic and political security- Countries without their own source of fossil fuels are affected by change in price and availability.
What are some disadvantages of biofuels?
- Land use- Forests are being destroyed to create land to grow the plants for biofuels.
- Use of resources- Large quantities of water and fertiliser needed to grow biofuels.
- Carbon neutrality?- This does not take into account the fuel needed to build factories and transport of raw materials.
How can alcohols be dehydrated?
By removing water and forming a double bond, creating alkenes.
What are some dehydrating agents used to dehydrate alcohols?
Heated aluminium oxide or concentrated sulphuric acid.
What is a primary alcohol?
The OH is joined to a carbon that is joined to one other carbon.
What is a secondary alcohol?
The OH is joined to a carbon that is joined to two other carbons.
What is a tertiary alcohol?
The OH is joined to a carbon that is joined to three other carbons.
Describe the oxidation of primary alcohols
Primary alcohols -> Aldehydes -> Carboxylic acids.
Describe the oxidation of secondary alcohols
Secondary alcohols -> Ketones.
What product of oxidation has the functional group COH?
Aldehyde.
What product of oxidation has the functional group COOH?
Carboxylic acids.
What product of oxidation has the functional group CO?
Ketones.
Why can tertiary alcohols not be oxidised?
As there is no hydrogen on the adjacent carbon that can be lost.
What oxidising agent is used in the oxidation of alcohols?
Acidified potassium dichromate (VI).
What test can be used for primary and secondary alcohols?
Add acidified potassium dichromate (VI), and a colour change from orange to green will be observed.
What are carboxylic acids?
A homologous series containing COOH as the functional group. They are weak acids so only partly disassociate in an aqueous solution to form H+ ions.
How does a carboxylic acid react with bases and alkalis?
Base + Acid —> Salt + Water.
How does a carboxylic acid react with carbonates and hydrocarbons?
Carbonates + Acid —> Salt + Water + Carbon dioxide.
How does a carboxylic acid react to form an ester?
Carboxylic acid + Alcohol —> Ester + Water.
How is the ester made in esterification separated from the products?
Using distillation.
What is the catalyst in esterification?
Concentrated sulphuric acid to allow the alcohol, carboxylic acid and sulphuric acid are all heated together.
How are esters recognised?
They have a characteristic sweet, fruity smell and low boiling point.
How can you identify a carboxylic acid?
Add sodium carbonate and CO2 bubbles are produced. This turns limewater cloudy when bubbled through it.
