CCEA A Level Chemistry
CCEA A Level Chemistry 2.2 Nomenclature and Isomerism in Organic Compounds Exam Questions
Free CCEA A Level Chemistry revision for 2.2 Nomenclature and Isomerism in Organic Compounds: what you need to know, common mistakes and exam-style questions with answers. Covers homologous series, functional groups, IUPAC naming up to six carbons, structural and skeletal formulae, structural isomers and E/Z isomerism.
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About CCEA A Level Chemistry 2.2 Nomenclature and Isomerism in Organic Compounds
Section 2.2 of Unit AS 2 introduces the language of organic chemistry. You need the terms homologous series, functional group, structural isomerism and geometric isomerism, IUPAC names for compounds with up to six carbons in the main chain, and how to draw structural, displayed and skeletal formulae. You must draw and name structural isomers of acyclic aliphatic compounds and explain E/Z isomerism, which arises from restricted rotation about the C=C bond. This section is used throughout the rest of the course, from alkanes and alkenes in AS 2 to optical isomerism in A2 1, so precise naming habits pay off everywhere.
What you need to know
- Homologous series A family of compounds with the same functional group and general formula, where each member differs by CH2 and shows a gradual change in physical properties.
- IUPAC naming Find the longest carbon chain (up to six carbons), number from the end giving the functional group or branch the lowest number, and list substituents alphabetically with numbers, for example 2-methylbutane and 3-chloropentane.
- Formulae Structural formulae show each carbon with its atoms, such as CH3CH2OH; displayed formulae show every bond; skeletal formulae show carbon chains as zigzag lines with functional groups drawn in.
- Structural isomers Same molecular formula, different structural formula. They may differ in chain (branching), position of a functional group, or functional group.
- E/Z isomerism Needs a C=C bond, which cannot rotate, and two different groups on each carbon. Z isomers have the higher priority groups on the same side; E isomers have them on opposite sides. Cis and trans can be used when the same group is on each carbon.
Common mistakes in 2.2 Nomenclature and Isomerism in Organic Compounds
- Numbering from the wrong end of the chain. Give the functional group or substituents the lowest possible numbers.
- Drawing the same molecule twice and calling them isomers. Check whether rotating or flipping one drawing gives the other.
- Saying but-1-ene has E/Z isomers. One carbon of the C=C carries two hydrogens, so it cannot.
- Missing hydrogens or carbons in skeletal formulae. Each line end and vertex is a carbon with enough hydrogens to make four bonds.
- Forgetting commas and hyphens in names. Use commas between numbers and hyphens between numbers and words, for example 2,2-dimethylpropane.
Try three 2.2 Nomenclature and Isomerism in Organic Compounds exam-style questions
1. Name and draw the three structural isomers of C5H12. (3 marks)
Show the mark scheme answer
Pentane; 2-methylbutane; 2,2-dimethylpropane (correct structures).
2. Explain why but-2-ene has E/Z isomers. (2 marks)
Show the mark scheme answer
Restricted rotation about the C=C double bond; each carbon of the double bond has two different groups attached (H and CH3).
3. Give the IUPAC name of CH3CH(Cl)CH2CH3. (1 mark)
Show the mark scheme answer
2-chlorobutane.
2.2 Nomenclature and Isomerism in Organic Compounds FAQs
What does CCEA A Level Chemistry 2.2 Nomenclature and Isomerism cover?
It covers homologous series, functional groups, IUPAC naming to six carbons, structural, displayed and skeletal formulae, structural isomerism and E/Z isomerism.
Which unit is 2.2 examined in?
It is examined in Unit AS 2: Further Physical and Inorganic Chemistry and an Introduction to Organic Chemistry, a 1 hour 30 minute paper with a multiple-choice section and structured questions. Related practical skills can also be assessed in Unit AS 3.
How do I find all the structural isomers of a formula?
Work systematically: start with the straight chain, then move a methyl group along, then try two branches, and check each new drawing really is different by naming it.
