3.5 Alcohols Flashcards
(31 cards)
What is the functional group of alcohols
-OH
What is the general formula of an alcohol
CnH2n+1OH
What are the 2 methods used to produce ethanol
- Hydration of ethene
- Fermentation
What is hydration of alcohols
Producing alcohols from alkenes.
What are the conditions required for the hydration of alcohols
- Concentrated acid catalyst (e.g. sulfuric or phosphoric acid)
- Aqueous conditions (presence of water)
- Temperature of 300 degrees celcius
- High pressure (around 70atm)
What is an advantage of the hydration method for producing ethanol
Produces a very high yield as ethanol is the only product, making it the favoured method as an industrial process.
What is fermentation
Production of ethanol from glucose.
What are 2 advantages of fermentation for the production of ethanol
- This method is cheaper than hydration as it is carried out at much lower temperatures
- The ethanol produced can be used as a biofuel as it is said to be carbon neutral
What does carbon neutral mean
The carbon given out when it is burned is equal to the carbon taken in by the crops during the growing process.
What 3 equations show that the production of ethanol as a biofuel is a carbon neutral process and what are these reactions
Fermentation:
- C6H12O6 => 2C2H5OH + 2CO2
Combustion:
- 2C2H5OH + 6O2 => 4CO2 + 6H2O
Photosynthesis:
- 6CO2 + 6H2O => C6H12O6 + 6O2
What are the conditions for fermentation
- Temperature kept between 15 to 35 degrees celcius
- Absence of oxygen
- Yeast used as catalyst
What is a disadvantage of fermentation for the production of ethanol
It can only produce a 15% yield of ethanol as once the concentration gets higher, the enzymes in yeast are killed off.
What is a primary alcohol
The carbon attached to the alcohol functional group is bonded to one other R group.
What is a secondary alcohol
The carbon attached to the alcohol functional group is bonded to two other R group.
What is a tertiary alcohol
The carbon attached to the alcohol functional group is bonded to three other R group.
What are the 2 possible products when oxidising a primary alcohol
- Aldehydes
- Carboxylic acids
What is the oxidising agent used for the oxidation of alcohols
Acidified potassium dichromate (K2Cr2O7/H+).
What are the products of oxidising a secondary alcohol
Ketones
What colour change is observed when an alcohol is oxidised
The acidified potassium dichromate causes the solution to turn from orange to green.
Can tertiary alcohols be oxidised
No.
How are alkenes formed from alcohols
Dehydration of alcohols where water is removed from the molecule.
What are the conditions needed for the dehydration of alcohols
- Excess of hot concentrated sulfuric acid (catalyst)
- Aluminium oxide catalyst
How does the reaction mechanism show that the acid acts as a catalyst
The H+ acidic ions are reformed.
What is the functional group of an aldehyde
-CHO
