Formulas, functional groups and the naming of organic compounds
Cambridge A-Level Chemistry (9701) · Unit 29: An introduction to A Level organic chemistry · 8 flashcards
Formulas, functional groups and the naming of organic compounds is topic 29.1 in the Cambridge A-Level Chemistry (9701) syllabus , positioned in Unit 29 — An introduction to A Level organic chemistry , alongside Characteristic organic reactions. In one line: A functional group is a specific group of atoms within a molecule that is responsible for the characteristic chemical reactions of that molecule. Examples include hydroxyl (-OH) in alcohols and carboxyl (-COOH) in carboxylic acids.
Marked as A2 Level: examined at A Level in Paper 4 (A Level Structured Questions) and Paper 5 (Planning, Analysis and Evaluation). It is not tested on the AS-only papers (Papers 1, 2 and 3).
The deck below contains 8 flashcards — 1 definition and 7 key concepts — covering the precise wording mark schemes reward. Use the definition card to lock down command-word answers (define, state), then move on to the concept and calculation cards to handle explain, describe, calculate and compare questions.
Some cards in this deck are on other syllabus topics: 13.1 Formulas, functional groups and the naming of organic compounds. Each card is labelled with its topic.
Functional group in organic chemistry
A functional group is a specific group of atoms within a molecule that is responsible for the characteristic chemical reactions of that molecule. Examples include hydroxyl (-OH) in alcohols and carboxyl (-COOH) in carboxylic acids.
What the Cambridge 9701 syllabus says
2025-2027 syllabus, in our words · A2 LevelWhat the syllabus expects you to be able to do in this topic, in plain English. For the exact wording, see the official syllabus (PDF).
- Understand that each of these classes (arenes, halogenoarenes, phenols, acyl chlorides, secondary and tertiary amines, primary, secondary and tertiary amides, and amino acids) has a functional group that controls its physical and chemical properties.
- Interpret and use skeletal, displayed, structural and general formulas for each class listed in outcome 1 above; you are not expected to draw a displayed formula for a molecule that contains a benzene ring.
- Understand and apply systematic naming for simple aliphatic organic molecules of up to six carbon atoms (up to six on each side in esters and amides) that contain the functional groups of the classes in outcome 1 above, including cyclic compounds with one ring of up to six carbon atoms. Esters and nitriles must be unbranched, and you do not need to name secondary or tertiary amines.
- Understand and apply systematic naming for simple aromatic molecules containing one benzene ring that carries a single simple substituent or several, e.g. 3-nitrobenzoic acid and 2,4,6-tribromophenol.
Also in this deck: 13.1 Formulas, functional groups and the naming of organic compounds
- Define a hydrocarbon: a compound containing only carbon and hydrogen atoms.
- Understand that an alkane is a simple hydrocarbon without any functional group.
- Understand that each class of compound in the syllabus table (alkenes, halogenoalkanes, alcohols, aldehydes, ketones, carboxylic acids, esters, primary amines and nitriles) has a functional group that determines its physical and chemical properties.
- For every compound class named in outcome 3 above, interpret and use its skeletal, displayed, structural and general formulas.
- Understand and use systematic names for simple aliphatic molecules of up to six carbon atoms that contain the functional groups listed in outcome 3 above (up to six carbons on each side of an ester; esters and nitriles must be unbranched).
- Deduce a compound's molecular formula, empirical formula or both from its skeletal, displayed or structural formula.
Cambridge syllabus keywords to use in your answers
These are the official Cambridge 9701 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.
Topic 29.1 · Formulas, functional groups and the naming of organic compounds
What is a functional group in organic chemistry?
A functional group is a specific group of atoms within a molecule that is responsible for the characteristic chemical reactions of that molecule. Examples include hydroxyl (-OH) in alcohols and carboxyl (-COOH) in carboxylic acids.
Topic 13.1 · Formulas, functional groups and the naming of organic compounds
Draw the structural formula for butan-2-ol.
CH3-CH(OH)-CH2-CH3. The '2' indicates that the hydroxyl group (-OH) is attached to the second carbon atom in the butane chain.
Topic 13.1 · Formulas, functional groups and the naming of organic compounds
Draw the displayed formula for pentanal.
Pentanal is CH₃CH₂CH₂CH₂CHO. In the displayed formula every bond is drawn: a chain of five carbon atoms, where the CH₃ carbon at one end has three H atoms, the next three carbons have two H atoms each, and the aldehyde carbon at the other end has one H atom and a C=O double bond to oxygen.
Topic 13.1 · Formulas, functional groups and the naming of organic compounds
What is the skeletal formula of 3-methylhexane?
A zig-zag line with six points representing the carbon chain, and a methyl group (one line) branching off the third carbon.
Topic 13.1 · Formulas, functional groups and the naming of organic compounds
Give the systematic name for the compound with the structural formula CH3CH2COOCH3.
Methyl propanoate. It is an ester derived from propanoic acid and methanol.
Topic 13.1 · Formulas, functional groups and the naming of organic compounds
Name the compound with the formula CH3CH2CH2CN, using systematic nomenclature.
Butanenitrile. The 'nitrile' suffix indicates the presence of the -CN functional group, and 'butane' indicates a four-carbon chain.
Topic 13.1 · Formulas, functional groups and the naming of organic compounds
Draw the skeletal formula of 2,4-dimethylpentane.
A zig-zag line representing the five-carbon pentane chain, with single lines branching off the second and fourth carbons, representing the two methyl groups.
Topic 29.1 · Formulas, functional groups and the naming of organic compounds
What is the systematic name for the aromatic compound C₆H₅NO₂, a benzene ring with one nitro group?
Nitrobenzene. No position number is needed, because all six ring carbons are equivalent when there is only one substituent. Numbers (or ortho/meta/para) are used only when there are two or more substituents, e.g. 1,3-dinitrobenzene.
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Formulas, functional groups and the naming of organic compounds sits alongside these A-Level Chemistry decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.
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