Apply meta directing effects
Predict meta substitution from –NO₂, –COOH and –COR groups using the stated A Level scope.
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 positions are meta to a substituent at carbon 1?
What you will learn
- Identify meta positions relative to a substituent
- Predict meta direction from –NO₂, –COOH and –COR
- Use the list without extending it to unstudied substituents
The listed electron-withdrawing groups direct meta
The syllabus identifies –NO₂, –COOH and –COR as groups that direct an incoming electrophile to the meta positions of an aromatic ring.
With a group at position 1, the meta positions are 3 and 5. For a ring with several substituents, first identify the directing group named or intended by the question and state the predicted position relative to it.
Use a qualitative reason
These groups withdraw electron density from the ring through the attached electron-withdrawing functionality. The syllabus-level rule is that they direct substitution toward meta positions.
Do not treat all groups containing oxygen as the same director: –OH directly attached to a ring is ortho/para directing, while –COOH and –COR are meta directing in the specified list.
Pause and explain
Which listed group directs electrophilic substitution mainly meta?
Worked example
Where does a new electrophile enter relative to –NO₂ at ring carbon 1?
Show the worked solution
- Meta positions from carbon 1 are 3 and 5.
- –NO₂ is listed as a meta director.
- Predict substitution mainly at positions 3 and 5.
Answer The nitro group directs electrophilic substitution mainly to positions 3 and 5.
Try a topic test
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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 benzoic-acid ring has –COOH at position 1. Where does this group direct a new electrophile?
Give me a hint
Use –COOH's listed directing category.
Compare my reasoning
- –COOH is a meta director.
- Meta positions from 1 are 3 and 5.
- Predict those positions qualitatively.
Mainly positions 3 and 5 relative to the carboxyl group.
Look for these in your work
- Director identified
- Positions numbered
- Prediction stated
Classify –COR at position 1 and predict the main ring positions for a second substitution.
Give me a hint
Do not mistake the carbonyl substituent for an –OH group.
Compare my reasoning
- –COR is in the listed meta-directing set.
- Meta positions are 3 and 5.
- State the prediction relative to position 1.
–COR directs mainly to positions 3 and 5.
Look for these in your work
- Group read correctly
- Positions identified
- Reference position stated
A learner says a ring-bound –OH group must be meta directing because it contains oxygen. Explain the error.
Give me a hint
Compare the complete group attached to the ring, not the element alone.
Compare my reasoning
- A ring-bound –OH is phenol and is ortho/para directing.
- –COOH and –COR are different oxygen-containing groups and are meta directors.
- Directing effects depend on connectivity and electron effect.
The attached group is –OH, not –COOH or –COR. Phenol directs ortho/para; group connectivity, not merely the presence of oxygen, determines the listed effect.
Look for these in your work
- Actual group identified
- Contrasting groups distinguished
- Connectivity principle explained
Common mistakes
- Calling –NO₂ an ortho/para director
- Confusing –COOH with –OH
- Failing to state positions relative to the existing group
- Applying meta direction to –COR without recognising it is attached through carbonyl carbon
What can you explain now?
Which positions are meta to a substituent at carbon 1?
Compare with the explanation
3 and 5
The meta positions are two ring steps from carbon 1.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Which positions do –NO₂, –COOH and –COR direct toward, and how does that differ from –OH?
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.