Download OCR Chemistry A Structural isomerism Specification references 4.1

OCR Chemistry A
11.4 Isomerism
Teacher and Technician notes
Structural isomerism
Specification references

4.1.1 e)

M 4.2
Aims
This exercise will give the students practise at naming organic molecules. It should in particular
help students who have difficulty visualising molecules. Using a modelling kit, students will be
able to model isomerism in three dimensions.
Learning outcomes
After completing the practical students should be able to:

understand what is meant by structural isomerism

use ideas about structural isomerism to identify and name isomers of alkanes, alcohols,
aldehydes, ketones, carboxylic acids, and esters.
Teacher notes

This exercise is a good way of engaging students with concepts that are hard to visualise.
Using molecular modelling kits enables a hands-on approach and can quickly show students
how molecules and isomers are formed.
Answers for method sheet
Molecular
formula
Structural formula
Shortened structural
formula
IUPAC, or systematic,
name
1
C2H6O
CH3CH2OH
Ethanol
2
CH4
CH4
Methane
© Oxford University Press 2015
www.oxfordsecondary.co.uk/acknowledgements
This resource sheet may have been changed from the original
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OCR Chemistry A
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11.4 Isomerism
Teacher and Technician notes
3
C2H6
CH3CH3
Ethane
4
C4H10
CH3CH2CH2CH3
Butane
5
C4H10
CH3CH(CH3)CH3
2-Methylpropane
6
C3H8O
CH3CH2CH2OH
Propan-1-ol
7
C3H8O
CH3CH2(OH)CH3
Propan-2-ol
8
C6H12
(CH2)6
Cyclohexane
Molecules 4 and 5 are structural isomers.
Molecules 6, 7, and 8 are structural isomers.
These molecules are structural isomers because they have the same molecular formulae,
but different structural formulae.
© Oxford University Press 2015
(1 mark)
(1 mark)
(1 mark)
(1 mark)
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This resource sheet may have been changed from the original
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OCR Chemistry A
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11.4 Isomerism
Teacher and Technician notes
Students are likely to give the first four of these isomers of C4H10O. The final two isomers
given here are ethers which are not covered in the course. These could be introduced to
more able students as an extension to the question.
(6 marks)
butan-1-ol
butan-2-ol
2-methylpropan-1-ol
2-methylpropan-2-ol
ethoxyethane
methoxypropane
© Oxford University Press 2015
www.oxfordsecondary.co.uk/acknowledgements
This resource sheet may have been changed from the original
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11.4 Isomerism
Teacher and Technician notes
OCR Chemistry A
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Award a maxiumum of 5 marks for each of part a and b
a Correctly drawn species (as in diagram below)
b Correctly named molecules (as in diagram below)
(5 marks)
(5 marks)
Answers for follow up sheet
1
Alkanes are a group of hydrocarbons which have the general formula CnH2+2.
a C5H12
b Award 1 mark for each correct structure.
c Award 1 mark for each correct name.
(1 mark)
Skeletal
formula
Name
2
Pentane
2-methylbutane
2,2-dimethylpropane
Award 1 mark for each correct structure, 1 mark for each correct name.
Displayed
formula
Name
3
a
Propanal
Propanone
Draw out the displayed formula and name both of the carboxylic acids which have the
molecular formula C4H8O2.
(4 marks)
Displayed formula of carboxylic acids with
the molecular formula C4H8O2
Displayed
formula
1 mark for each correct structure
Name
© Oxford University Press 2015
1 mark for each correct name
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11.4 Isomerism
Teacher and Technician notes
OCR Chemistry A
b
Award 1 mark for each correct structure
(4 marks)
Displayed formulae of esters with the molecular formula C4H8O2
1 mark for each correct structure
4
a
b
Award 1 mark for each correctly drawn structure for isomers with formula C3H7Cl.
Award 1 mark for each correctly named structure.
(4 marks)
(4 marks)
Support
This activity assumes that students have covered the main functional groups in organic chemistry
encountered across the whole course including alkanes, alkenes, alcohols, aldehydes, ketones,
carboxylic acids, and esters. Although alkenes are not covered in this activity, as they also
exhibit stereoisomerism, students could be encouraged to try to work out that cyclic alkanes and
aliphatic alkenes are structural isomers of each other. Further ideas to stretch students could
include finding all the isomers of cyclic alkanes, for example C4H8 and C5H10.
© Oxford University Press 2015
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This resource sheet may have been changed from the original
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OCR Chemistry A
11.4 Isomerism
Teacher and Technician notes
Technician notes
Safety

There are no safety hazards with this exercise.
Equipment and materials
The following will be required for each student, or each group of students.

Molymod kits or molecular modelling kits
© Oxford University Press 2015
www.oxfordsecondary.co.uk/acknowledgements
This resource sheet may have been changed from the original
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