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AQA A Level Chemistry

3.3.5
Alcohols

Section 3.3.5 covers the production of ethanol by hydration of ethene and by fermentation, biofuels and the carbon-neutral argument, the classification of alcohols, oxidation with acidified potassium dichromate(VI) to aldehydes, carboxylic acids and ketones with the tests that distinguish them, and the acid-catalysed elimination of water to form alkenes with its mechanism. The techniques page supports required practical 5.

Exam Paper
Paper 2
7405/2
Specification Points
3.3.5.1 – 3.3.5.3
3 sections covered
Topic Parts
5 pages
Revision notes available
Exam Board
AQA
7405 (2015 onwards)

Revision Notes

Work through 3.3.5 Alcohols in a structured sequence.

The –OH group
Naming and
Classifying
1
Available

Alcohols: Naming, Classification and Properties

Alcohols: nomenclature, structural, displayed and skeletal formulae, primary, secondary and tertiary alcohols, hydrogen bonding, boiling temperatures and solubility.

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Two routes
Producing
Alcohols
2
Available

Producing Alcohols: Hydration, Fermentation and Biofuels

Producing ethanol: hydration of ethene, fermentation of glucose, conditions and comparison, biofuels and carbon neutrality.

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Orange to green
Oxidation of
Alcohols
3
Available

Oxidation of Alcohols

The oxidation of alcohols: acidified dichromate(VI), aldehydes, carboxylic acids and ketones, distillation versus reflux, [O] equations and tests for aldehydes and acids.

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Reaction map
Reactions of
Alcohols
4
Available

Substitution and Elimination Reactions of Alcohols

Reactions of alcohols: combustion, halogenation with PCl₅, KBr and sulfuric acid, and red phosphorus and iodine, and dehydration to alkenes.

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Practical skills
Preparing and
Purifying
5
Available

Preparing and Purifying Organic Liquids

Preparing and purifying organic liquids: reflux, distillation, separating funnel, drying agents, boiling temperature and percentage yield.

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Specification Coverage

3.3.5 Alcohols – AQA A Level Chemistry

The following AQA specification points outline the knowledge and skills students are expected to demonstrate. Wording follows the AQA A Level Chemistry (7405) specification.

3.3.5.1 Alcohol production

3.3.5.1i
know that alcohols are produced industrially by hydration of alkenes in the presence of an acid catalyst
3.3.5.1ii
know that ethanol is produced industrially by fermentation of glucose and know the conditions for this process
3.3.5.1iii
know that ethanol from fermentation is separated by fractional distillation and can be used as a biofuel
3.3.5.1iv
explain the meaning of the term biofuel
3.3.5.1v
justify the conditions used in the production of ethanol by fermentation of glucose
3.3.5.1vi-a
write equations to support the statement that ethanol produced by fermentation is a carbon neutral fuel
3.3.5.1vi-b
give reasons why the statement that ethanol produced by fermentation is a carbon neutral fuel is not valid
3.3.5.1vii
outline the mechanism for the formation of an alcohol by the reaction of an alkene with steam in the presence of an acid catalyst
3.3.5.1viii
discuss the environmental and ethical issues linked to decision making about biofuel use

3.3.5.2 Oxidation of alcohols

3.3.5.2i
know that alcohols are classified as primary, secondary and tertiary
3.3.5.2ii-a
know that primary alcohols can be oxidised to aldehydes
3.3.5.2ii-b
know that aldehydes from primary alcohols can be further oxidised to carboxylic acids
3.3.5.2iii
know that secondary alcohols can be oxidised to ketones
3.3.5.2iv
know that tertiary alcohols are not easily oxidised
3.3.5.2v
know that acidified potassium dichromate(VI) is a suitable oxidising agent for alcohols
3.3.5.2vi
write equations for oxidation reactions of alcohols using [O] as oxidant
3.3.5.2vii
explain how the method used to oxidise a primary alcohol determines whether an aldehyde or carboxylic acid is obtained
3.3.5.2viii-a
use Fehling’s solution to distinguish between aldehydes and ketones
3.3.5.2viii-b
use Tollens’ reagent to distinguish between aldehydes and ketones

3.3.5.3 Elimination

3.3.5.3i
know that alkenes can be formed from alcohols by acid-catalysed elimination reactions
3.3.5.3ii
know that alkenes produced this way can be used to produce addition polymers without monomers derived from crude oil
3.3.5.3iii
outline the mechanism for the elimination of water from alcohols