Alcohol
A concise revision guide to the alcohol functional group, the hydroxyl group, the -ol suffix, naming diols and triols, and the priority of the -OH group in organic nomenclature.
GCSE Recap: The Alcohols You Already Know
Three quick questions on the alcohols you met at GCSE.
What Is an Alcohol?
An alcohol is an organic compound containing the hydroxyl functional group, written as -OH.
The oxygen atom in the -OH group is bonded to a carbon atom in the organic molecule. This functional group determines the characteristic chemistry of alcohols.
In naming, the -OH group is usually shown using the suffix -ol.
Key idea: The alcohol functional group is the hydroxyl group, -OH. Do not confuse this with the hydroxide ion, OH–.
The hydroxyl group is the identifying functional group of alcohols and is written as -OH in organic formulae.
Quick Check: Spot the Alcohol
Only one of these four compounds has a hydroxyl group bonded to a carbon atom of the chain.
Naming Alcohols Using the -ol Suffix
Alcohols are named using the suffix -ol.
If the position of the -OH group needs to be shown, the position number is placed between the name stem and the -ol suffix.
For example, propan-1-ol has a three-carbon chain and the -OH group is attached to carbon 1.
| Homologous series | Functional group | Prefix | Suffix | Example |
|---|---|---|---|---|
| Alcohols | -OH | hydroxy- | -ol | propan-1-ol |
The number 1 shows that the -OH group is bonded to the first carbon atom in the propyl chain.
Quick Check: Name That Alcohol
Choose the correct name for each new alcohol.
Alcohols with Two or More -OH Groups
If a molecule contains two or more -OH groups, prefixes such as di- and tri- are used.
In these cases, the final e in the alkane stem is retained before the suffix. For example, ethane becomes ethane-1,2-diol, not ethan-1,2-diol.
Two -OH groups
Use -diol, with numbers showing the positions of both -OH groups.
Three -OH groups
Use -triol, with numbers showing the positions of all three -OH groups.
Ethane-1,2-diol contains two -OH groups, so the diol suffix is used and the e in ethane is retained.
Propane-1,2,3-triol contains three -OH groups, so each position is included before the triol suffix.
Quick Check: Diols and Triols
Type the missing numbers in the names of these diols and triols.
Priority of the -OH Group
The -OH group has higher priority than both halogenoalkanes and alkenes when naming organic molecules.
This means the carbon chain is numbered so that the -OH group is on the lowest possible carbon, often carbon 1.
If a molecule also contains a C=C double bond or halogen substituents, these are still included in the name, but the -OH group controls the main suffix and the numbering direction.
Exam focus: When several groups are present, first identify the highest-priority group that will control the suffix and numbering.
The -ol suffix and carbon 1 position are used because the -OH group has higher naming priority than the C=C bond and chloro substituents.
Quick Check: Explain the Numbering
Write a short explanation of why the -OH group controls the numbering of this bromoalcohol.
When Alcohol Is Named as Hydroxy-
If a compound contains an -OH group and another functional group with higher priority, the higher-priority group takes the suffix form.
In that situation, the -OH group is named using the prefix hydroxy-.
This is why it is important to recognise whether -OH is acting as the main functional group or as a substituent in the name.
| Naming situation | How -OH appears in the name | Example naming logic |
|---|---|---|
| -OH is the main functional group | Use the suffix -ol | propan-1-ol |
| A higher-priority group controls the suffix | Use the prefix hydroxy- | The higher-priority group takes the suffix form |
Remember: The usual alcohol naming pattern is -ol, but hydroxy- is used when the -OH group is not the highest-priority group.
Quick Check: When -OH Becomes Hydroxy-
Name a compound in which the -OH group is not the highest-priority group.
Master Introduction to Organic Chemistry and Alkanes for AQA A Level Chemistry
Continue from these free revision notes into the full 3.3.1 and 3.3.2 Introduction to Organic Chemistry and Alkanes course. The six guided video lessons are ready now; the AQA MCQ bank, teacher-marked short-answer questions, supplementary lessons and KASP spec-point report are being written, and the course opens for enrolment as soon as they are complete.
Guided video teaching
Learn the chemistry and exam technique through structured video lessons with worked examples and walkthroughs.
Instant MCQ feedback
Auto-marked MCQ quizzes provide immediate diagnostic feedback for every answer choice.
Teacher-marked SAQs
Submit written exam responses and receive chemistry specialist feedback with improvement guidance.
Progress tracking
Identify strengths and weaknesses across the full 3.3.1 and 3.3.2 specification with targeted reporting.
See how the course works
Click play to start the course preview animation.
Some ionic radii are shown.
| Ion | Ionic radius / nm |
|---|---|
| Na+ | 0.102 |
| K+ | 0.138 |
| F− | 0.133 |
| Cl− | 0.180 |
Which compound has the strongest ionic bonding?
Explain why the metallic bonding in magnesium is much stronger than that in sodium.
Copyright notice: This OLS revision content, including the explanations, layout, diagrams, tables and embedded learning structure, is authored for Online Learning System by Dr. Mohammed Al-Fatah. It may not be copied, reproduced, redistributed or adapted without written permission.
Keep this note — free
Save your progress across every AQA topic. A free account remembers which topics you have covered, saves your question scores, and syncs across your phone and laptop.
- Track every topic you have finished
- Keep your practice-question scores
- No payment, no card, free forever
Already registered? Log in