Alcohols Revision Notes

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  • Created on: 08-04-16 12:07
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Alcohols
Nomenclature of Alcohols
C
nH n+1OH
e.g. Ethanol
longest carbon chain is 2 C atoms so ethane.
There's 1 ­OH suffix ­ol
Could be attached to 2 C atoms but they are equivalent so both labelled C atom 1 so no
need to put a No. So alcohol is ethanol
e.g. 2methylpropan2ol
Longest C chain = 2 so propane
1 ­OH so suffix = ol
Also methyl group on 2nd C so 2methyl prefix
Called 2methylpropan2ol
e.g. ethane ­ 1, 2 diol
Longest C chain = 2 so ethane
2 ­OH so suffix = diol
1 ­OH on each carbon so 1,2 before ­diol
Primary, secondary, tertiary
Depends on which C the hydroxyl group (OH) is bonded to.
Primary given notation of 1° and ­OH attached to C with 1 alkyl group.
Secondary given notation 2° and ­OH attached to C with 2 alkyl groups.
Tertiary given notation 3° where ­OH group attached to carbon with 3 alkyl groups
attached.

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Ethanol Production
Hydrating Alkenes
Using steam in presence of acid catalyst:
General equation CnH2n + H2O CnH2n+1OH
Used industrially to produce ethanol. Ethen can be hydrated by steam at 300°C and pressure of
60atm. It needs solid phosphoric acid catalyst.
Equation for industrial hydration of ethane ­ CH2=CH
2(g) +
H2O(g)
CH
3CH 2OH(g)
Reversible and yield low (only 5%)
Mechanism
Fermentation of Glucose
Will be more useful in future when crude oil supplies start running out, petrochemicals like
ethane will be expensive.…read more

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Yeast produces enzymes which converts glucose to ethanol and carbon dioxide.
When solution reaches 15% ethanol, yeast dies. Fractional distillation used to inc. conc of
ethanol. Fermentation uses cheap equipment and renewable resources but the step
needed to purify the ethanol using this method takes extra time and money.
Biofuels
Made from biological material that recently died.…read more

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When ethanol burned, carbon dioxide and water produced
These 3 equations show that overall the same No. moles of Carbon dioxide is used as given out.
However fossil fuels will need to be burned to power machinery to make fertilisers for crops and
machinery to harvest them. Refining and transporting them will also use energy so not completely
carbon neutral.
Oxidising Alcohols
Could Burn them or use oxidising agent ­
Acidified potassium dichromate (VI) ion, K
2Cr
2O 7 which mildly oxidises 1°and 2° alcohols.…read more

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Have 2 alkyl groups attached to carbonyl carbon atom.
Suffix for ketones is ­one. For ketones with 5 or more C, you need to say which C the functional
group is on.
Carboxylic Acids
Have a COOH group at end of carbon chain.
General formula = C
nH2n+1COOH.
Suffix is ­oic. Also add word acid to end of name.
Oxidation of Primary Alcohols
1st oxidised to aldehyde which can then be oxidised to carboxylic acid.…read more

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It is tricky to control amount of heat and aldehyde is usually oxidised to form vinegar smelling
ethanoic acid.
To get just the aldehyde you need to get out of oxidising solution as soon as its formed. Do this by
gently heating excess alcohol with controlled amount of oxidising agent in distillation apparatus.
The aldehyde is distilled off immediately.
Oxidising Primary Alcohols to Carboxylic Acids
Alcohol must be vigorously oxidised.
Alcohol mixed with excess oxidising agent and
heated under reflux.…read more

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