C6 - Alcohols - OCR Gateway

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  • Created on: 01-05-13 20:33
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Alcohols
Alcohols are organic molecules which form a homologous series
with the general formula CnH2n+1OH.
Homologous means that they have similar properties and structure,
differing only in the number of CH2 units in the chain.
Methanol, CH3OH, has n=1. Butanol, C4H9OH, has n=4.
Ethanol, C2H5OH, has n=2. Pentanol, C5H11OH, has n=5.
Propanol, C3H7OH, has n=3. Hexanol, C6H13OH, has n=6.
One of the most common Alcohol is Ethanol, (C2H5OH)
Its displayed formula is
The 3 main uses of Ethanol are:
1. Petrol Replacements
2. As a solvent- industrial methylated spirits
3. Alcoholic drinks
Ethanol is made by a process called Fermentation, which uses plants
Glucose ethanol + carbon dioxide
Balanced Symbol Equation
C66H12O6 2C2H5OH + 2CO2
Fermentation requires:
Sugars from plants
Water
Enzymes from yeast
Temperature between 25C and 50C
Absence of Oxygen
The Process
Fermentation is a process which used to take place naturally, when yeast was blown on to ripe plants.
As well as the yeast, the process required a glucose solution and an optimum temperature was
required for the process to be successful.
In the process, the reaction is catalysed by the enzymes in the yeast, and this will only happen if there
is NO air.
The ethanol produced by Fermentation is dilute; (a thin solution which is less concentrated) therefore
it undergoes another process known as fractional distillation. The product obtained from this process
is almost pure ethanol.
The conditions required:
If the temperature is too cold, then the enzymes are inactive
If the temperature is too hot, then the enzymes become denatured
If air is present in then a completely different reaction takes place producing ethanoic acid

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Ethanol is made from a renewable source, biomass, however there is another source:
ETHENE
In this case, Ethanol is made from Ethene which is a product from crude oil or natural gas. Due to this
reason, ethanol made from Ethene is non-renewable.
However in the case of fermentation, Ethanol is made from biomass which is a renewable source,
therefore the Ethanol made from plants is a renewable fuel.
Ethanol is made by reacting Ethene with water, this is a hydration reaction.…read more

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