Chapter 33 – The Alcohols
Section A – Structure of the alcohols
Functional group = one or more of the hydrogen atoms of an alkane are replaced with an
_______(_____________) group
Methanol
Methanol is a _______ substance that can cause
death if consumed.
It is added to ethanol to make it undrinkable so is
called a _______________ agent
Ethanol is found in alcoholic drinks and is usually
made via a fermentation reaction using yeast
Ethanol
C6H12O6
2C2H5OH + CO2
Ethanol is a good solvent and is also used in paints,
perfumes and aftershaves.
It can also be used as a fuel and in
________________.
Butanol
Propanol
Types of alcohol
Primary alcohol
Example:
Secondary alcohol
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Chapter 33 – The Alcohols
Section B – Physical Properties
Boiling points
Alcohols have _____________ melting and boiling points than their corresponding alkanes.
This is due to :
Alcohol have a higher ________________________than their corresponding alkanes which leads to
more ________________ forces between molecules.
Alcohols ALSO have strong intermolecular _______________forces between molecules due to the
presence of the OH group, which itself is highly polar.
NB. The relative effect of the hydrogen bonding is stronger in the lower members of the
alcohols, compared to the higher members of the alcohols which have a longer non polar
alkyl chain.
Solubility in water
The lower members of the alcohols are very _____________ in water. The presence of the
OH group allows them to hydrogen bond with water efficiently.
The higher members of the alcohols are ____________ soluble in water. This is because in
these alcohols the non polar alkyl chain gets longer and its effect becomes more significant.
Section C – Chemical Reactions
1.
Combustion reactions
Alcohols react with oxygen to make carbon dioxide and _________. (exothermic reactions)
Example
C3H7OH + O2
CO2 + H20
Try to balance this equation!
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Chapter 33 – The Alcohols
2.
Elimination reactions
Alcohols undergo elimination reactions (where there is the loss of a small molecule) which in this
case is ______________, so these reactions can also be called dehydration reactions.
Example:
C2H5OH
C2H4 + H20
Note the change in the geometry of the carbon atoms!!
3. Oxidation of alcohols
Primary alcohols
Primary alcohols can be converted their corresponding aldehydes by the reaction with acidified
sodium dichromate. They can then be further oxidised to the corresponding carboxylic acid using the
same reagents, but under different conditions (________________________________________)!
Example
Ethanol
Ethanal
Ethanoic acid
Note the change in the geometry of the carbon atom attached to the OH group!
Other examples:
Propanol
Butanol
*** Note that the above reactions can be reversed in a reduction reaction by using a __________
catalyst and ______________ gas
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Chapter 33 – The Alcohols
3. Oxidation reactions of alochols continued
Secondary alcohols
Secondary alcohols can be converted their corresponding ketones by the reaction with acidified
sodium dichromate.
They CANNOT then be further oxidised to a carboxylic acid!!!
Example
Propan – 2- ol
Propanone
Other examples:
Butan- 2- ol
*** Note that the above reactions can be reversed in a reduction reaction by using a __________
catalyst and ______________ gas
4. Reaction with sodium
Alcohols are very weak acids and will donate their H+ ions, only when mixed with a very reactive
metals such as sodium.
Ethanol
+
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Sodium
Sodium ethanoate + Hydrogen gas
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Chapter 33 – The Alcohols
5. Esterification reactions
When an alcohol reacts with a carboxylic acid under acidic conditions, an ester and water are made.
These are types of ___________________ reactions, and can also be called a
_______________________ reaction.
Ethanol +
Ethanoic acid
Ethyl ethanoate
+
water
** Note that the geometry of the carbonyl carbon does NOT change in this reaction.
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Chapter 33 – The Alcohols
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Organic Chemistry - The Alcohols
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Structure of alcohols
Alcohols: structure and names up to C-4 (primary and secondary
alcohols only). Geometry of carbon atoms.
Understand the difference between a primary alcohol and a
secondary alcohol
Physical properties of the alcohols
[physical state and explanation of boiling points of the members of
the family compared to corresponding alkanes, and each other}
Solubility (qualitative only) in water and explanation and in non-polar
solvents
Comparison of the structure of alcohols with the structure of water.
Solubility of (a) methanol and (b) butan-1 -ol in (i) cyclohexane and (ii)
water.
Uses of alcohols
Ethanol uses- as a solvent and as motor fuels.
Fermentation as a source of ethanol; (equation required)
Use of fermentation in the brewing and distilling industries.
Methanol as a denaturing agent.
Reactions of alcohols
Oxidation of alcohols using Na2Cr2O7 to (i) aldehydes and (ii)
acids(equations required).
Oxidation of aldehydes using Na2Cr2O7 to acids (equations required).
Reduction of carbonyl compounds using H2/Ni catalyst. (equations
required).
Combustion reactions of alcohols (equations required)
Reactions of alcohols with sodium. (equations required)
Esterification reactions with alcohols (equations required)
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