Predict substitution positions from an existing director
Combine ring numbering with the specified directing-effect list to predict likely positions for a new substituent.
A Level; Cambridge International Chemistry 9701, 2028–2030 syllabus, Topic 30. Follow the listed reagents, catalysts, temperatures and reaction scope for benzene and methylbenzene. Directing effects are limited to –NH₂, –OH, –R, –NO₂, –COOH and –COR. Written practice is self-checked
Before you begin
- Use the Topic 29 model of benzene as a planar aromatic ring with a delocalised π system, and recognise electrophiles, nucleophiles and organic functional groups.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which set of positions corresponds to ortho/para direction from carbon 1?
What you will learn
- Map ortho, meta and para positions consistently
- Use the six listed directing groups to predict positions
- Explain a prediction while preserving the stated scope
Apply the rule in a repeatable order
First number the ring from the existing substituent at position 1. Next classify that substituent: –NH₂, –OH and –R direct ortho/para; –NO₂, –COOH and –COR direct meta. Then translate the category to positions 2/6/4 or 3/5.
When a question includes more than one substituent, the syllabus-level directing rule may present competing influences. If no relative influence is specified, state the candidate positions and identify which group you used rather than inventing a unique product ratio.
Position labels do not replace chemical reasoning
A correct answer should state both the group and its directing effect. For example, –NO₂ at carbon 1 directs meta, so positions 3 and 5 are favoured.
The outcome is limited to –NH₂, –OH, –R, –NO₂, –COOH and –COR. For any other substituent, use information supplied in the question instead of importing an unsupported rule.
Pause and explain
How should you handle a directing group not included in the stated list?
Worked example
A ring has –COOH at carbon 1. Identify the positions that its directing effect favours for a new electrophile.
Show the worked solution
- Classify –COOH as a meta director.
- Positions 3 and 5 are meta to carbon 1.
- State the prediction relative to that group.
Answer The carboxyl group favours substitution at positions 3 and 5.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
A ring has –NO₂ at position 1. Give the positions favoured for further electrophilic substitution and name the directing category.
Give me a hint
Read –NO₂ from the listed meta-directing set.
Compare my reasoning
- –NO₂ directs meta.
- Meta positions are 3 and 5.
- State the category and positions.
The nitro group is meta directing and favours positions 3 and 5.
Look for these in your work
- Group classified
- Positions numbered
- Category stated
A ring has –OH at position 1. A student says positions 3 and 5 are the principal directing positions. Correct the prediction.
Give me a hint
Use the listed direction for phenol.
Compare my reasoning
- –OH is ortho/para directing.
- Ortho positions are 2 and 6; para is 4.
- Replace 3/5 with the correct set.
The hydroxyl group favours positions 2, 4 and 6, not the meta positions 3 and 5.
Look for these in your work
- Group effect recalled
- Position mapping correct
- Prediction corrected
A ring has –R at position 1 and –NO₂ at position 4. The question asks specifically for the positions favoured relative to –NO₂. State them and explain how you avoid overstating the result.
Give me a hint
Use the requested reference group; note that there are two substituents.
Compare my reasoning
- –NO₂ is meta directing.
- Relative to position 4, meta positions are 2 and 6.
- The other substituent can also influence the outcome, so avoid claiming a unique ratio without more information.
Relative to –NO₂ at position 4, positions 2 and 6 are meta and are the positions its effect favours. Because –R also directs, a unique quantitative product prediction needs further context.
Look for these in your work
- Requested director used
- Ring positions mapped
- Competing influence qualified
Common mistakes
- Forgetting to say which group the prediction is relative to
- Using the wrong numbering when several substituents are drawn
- Reporting an exact product ratio from a qualitative directing rule
- Applying a memorised rule to a group outside the listed set
What can you explain now?
Which set of positions corresponds to ortho/para direction from carbon 1?
Compare with the explanation
2, 4 and 6
Ortho positions are 2 and 6; para is 4.
After trying it yourself, choose your next review. This is your self-assessment.
Your review choice appears on Today. Sign in to sync it across devices.
Make it stick
What order of checks helps you make a reliable directing-position prediction?
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.