Organic Formulae, Nomenclature and Isomerism
Displayed, structural and skeletal formulae, homologous series, IUPAC naming, structural isomerism, E/Z isomerism and optical isomerism.
How to study A-level Chemistry
Represent the species and process correctly, conserve atoms, charge and energy, calculate with units, then test the result against observations and chemical evidence.
Core concepts
Concept 1
Organic names encode the longest appropriate parent, functional-group priority, substituents and locants.
Exam cue: Identify the highest-priority functional group before choosing the parent and suffix.
Concept 2
Structural isomers share a molecular formula but differ in connectivity.
Exam cue: Apply the stated priority rules to each carbon of a C=C bond before assigning E or Z.
Concept 3
Stereoisomers share connectivity but differ in spatial arrangement because of restricted rotation or chirality.
Exam cue: Locate a tetrahedral carbon with four different substituents when identifying a simple chiral centre.
Risk pitfalls and guardrails
Choosing the longest carbon chain while ignoring the principal functional group.
Guardrail: Do not substitute a memorised equation, mechanism or trend until you have identified the species, conditions and chemical model required.
Calling conformations structural isomers.
Guardrail: Do not substitute a memorised equation, mechanism or trend until you have identified the species, conditions and chemical model required.
Assigning E/Z from visual left and right rather than substituent priority.
Guardrail: Do not substitute a memorised equation, mechanism or trend until you have identified the species, conditions and chemical model required.
Memory anchors
Homologous Series
A homologous series shares a functional group and general formula with gradual property trends.
Structural Isomer
Structural isomers have the same molecular formula but different atom connectivity.
E/Z Isomerism
E/Z isomerism requires restricted C=C rotation and two different groups on each carbon.
Chiral Centre
A simple chiral centre is a tetrahedral carbon bonded to four different groups.
Enantiomers
Enantiomers are non-superimposable mirror-image stereoisomers.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
What is the IUPAC name of CH₃CH₂CH₂CH₃?
What is the IUPAC name of CH₃CH(CH₃)CH₂CH₃?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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