Download C6 Alcohols

Alcohols – Revision Pack (C6)
The formula of ethanol:
The molecular formula for ethanol is C 2 H 5 OH – ethanol is made using the process of
fermentation:
Glucose  Ethanol + Carbon Dioxide
C 6 H 12 O 6  2C 2 H 5 OH + 2CO 2
Ethanol is made by the fermentation of a glucose solution:
-
The reaction is catalysed (sped up) by the enzymes in yeast
This ONLY happens in the absence of oxygen
The dilute liquid made then undergoes fractional distillation to produce
ethanol
There’s more than one alcohol?
The alcohols are a group of compounds which have the general formula C n H 2n+1 OH
Alcohol
Methanol
Molecular Formula
CH 3 OH
Ethanol
C 2 H 5 OH
Propanol
C 3 H 7 OH
Butanol
C 4 H 9 OH
Pentanol
C 5 H 11 OH
Displayed Formula
The table above shows the molecular and displayed formula of alcohols with one to
five hydrocarbons (there are MANY more) – REMEMBER these!
Only ethanol is made using fermentation, using very specific conditions:
1) If the temperature is too low, the enzymes in the yeast are inactive
2) If the temperature is too high, the enzymes in the yeast are denatured
3) If air somehow gets in, ethanol is not made – ethanoic acid is by a different
reaction
Alcohols – Revision Pack (C6)
Ethanol from Ethene:
Ethanol made using fermentation can also be used as a fuel. This is a renewable fuel
because the plants that make the sugar (glucose) for the process can be grown
VERY quickly.
Ethanol that is used in industry can also be made from ethene. Ethanol made in this
way is NON-renewable. This is because the ethene it is made from comes from fossil
fuels. These fossil fuels CANNOT be replaced and are a finite (limited) resource.
The reaction used to make ethanol from ethene is called hydration because water is
added to the ethene molecule:
Ethene + Water  Ethanol
C 2 H 4 + H 2 O  C 2 H 5 OH
A hot phosphoric acid catalyst is used in this reaction; ethene and steam are passed
over it.
Advantages and Disadvantages of Ethanol Production:
Processing
By Fermentation
35oC – LESS energy
needed
Batch (disadvantage)
By Hydration
Hot catalyst – MORE
energy needed
Continuous (advantage)
Sustainability
Sustainable (advantage)
Purification
Fractional Distillation
needed (disadvantage)
Low (disadvantage)
From a finite resource
(disadvantage)
Fairly pure on production
(advantage)
High (disadvantage)
Conditions
Percentage Yield / Atom
Economy
Alcohols – Revision Pack (C6)
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