Unit Overview
Introduction to organic chemistry
CIE A-Level ChemistryΒ· 5 min read π n/a
1. Unit at a glance
Organic chemistry is the study of carbon-based compounds, which form all living matter and most everyday synthetic materials. This unit establishes the common language all chemists use to describe organic molecules, so mastering the content here is critical for every organic topic that follows.
We progress from fundamental naming conventions, through classifying compounds and identifying isomers, to introducing the curly arrow notation used to explain how organic reactions occur, and finish by connecting bonding to the 3D shapes of organic molecules.
This unit includes the following core sub-topics:
Nomenclature
Learn IUPAC rules for naming straight-chain, branched and simple cyclic organic compounds.
β β β± 10 min
Functional groups and isomerism
Classify organic compounds by functional group and identify common types of structural and stereoisomerism.
β β β β± 15 min
Reaction mechanisms
Master curly arrow notation to describe bond breaking and formation in basic organic reaction mechanisms.
β β β β β± 12 min
Organic molecule shapes
Relate carbon hybridization to bond angles and 3D shapes of common organic functional groups.
β β β β± 8 min
2. Common Pitfalls
Wrong move:
Numbering the carbon chain incorrectly for compounds with multiple functional groups
Why:
Higher priority functional groups must get the lowest possible carbon number, which is often overlooked
Correct move:
Always identify the highest priority functional group first before numbering the parent carbon chain
Wrong move:
Drawing curly arrows starting from the wrong location
Why:
Curly arrows show movement of an electron pair, so they must start at the electron source
Correct move:
Start all curly arrows at a lone pair of electrons or an existing covalent bond
Wrong move:
Confusing structural and stereoisomerism
Why:
Students often misclassify isomers by ignoring differences in atomic connectivity
Correct move:
If connectivity of atoms differs, it is structural isomerism; only differing spatial arrangement is stereoisomerism
3. Quick Reference Cheatsheet
Concept / Rule | Key Summary |
|---|---|
IUPAC Naming Order | Identify parent chain β number to give highest priority group lowest number β name substituents alphabetically |
Functional Group Priority Order | Carboxylic acids > esters > aldehydes > ketones > alcohols > alkenes > alkanes |
Isomerism Types | Structural: chain, position, functional group; Stereoisomerism: cis-trans, optical |
Curly Arrow Rule | Shows movement of an electron pair; starts at electron source, ends at electron destination |
Bond Angles by Hybridization | = 109.5Β°, = 120Β°, = 180Β° |
Bond Fission Types | Homolytic: 1 electron to each atom β free radicals; Heterolytic: 2 electrons to one atom β ions |
What's Next
Begin your study of this unit with the first sub-topic on nomenclature to build your foundational naming skills. Once you complete all four sub-topics here, you will be ready to move on to the next unit covering hydrocarbons, where you will apply all the core concepts you learn in this unit.