Nitrate benzene and methylbenzene
Use concentrated nitric and sulfuric acids at 25–60°C to replace an aromatic hydrogen with a nitro group.
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 temperature range is specified for nitrating benzene?
What you will learn
- Recall the nitrating mixture and temperature range
- Identify nitrobenzene as the benzene nitration product
- Describe nitration as aromatic substitution
Use the specified nitrating mixture
Nitration uses a mixture of concentrated HNO₃ and concentrated H₂SO₄ at a temperature between 25°C and 60°C. Under these conditions, benzene forms nitrobenzene; a ring hydrogen is replaced by –NO₂.
The acid mixture generates the electrophile NO₂⁺ (the nitronium ion). Temperature is part of the syllabus condition: do not omit it or replace it with heating to a much higher value.
Balance substitution and track the ring
The overall equation is C₆H₆ + HNO₃ → C₆H₅NO₂ + H₂O. The aromatic ring remains in the product; the incoming nitro group replaces one hydrogen.
Methylbenzene can also undergo ring nitration and gives positional nitromethylbenzene products. The methyl group directs substitution mainly to the 2- and 4-positions; use the stated product or conditions if the question narrows the isomer.
Pause and explain
Which electrophile attacks the aromatic ring in nitration?
Worked example
State the reagents, conditions and product for nitration of benzene.
Show the worked solution
- Mix concentrated nitric acid and concentrated sulfuric acid.
- Keep the temperature between 25°C and 60°C.
- Replace a ring H with –NO₂ to form nitrobenzene.
Answer Concentrated HNO₃ and concentrated H₂SO₄ at 25–60°C convert benzene to nitrobenzene and water.
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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.
Write the overall equation for benzene nitration and include the reaction conditions in words.
Give me a hint
Substitute one H with NO₂, then balance water.
Compare my reasoning
- Benzene is C₆H₆.
- The product is C₆H₅NO₂.
- The removed H combines with the OH from nitric acid to give water.
C₆H₆ + HNO₃ → C₆H₅NO₂ + H₂O; use concentrated HNO₃/H₂SO₄ at 25–60°C.
Look for these in your work
- Product formula correct
- Equation balanced
- Conditions complete
Why is nitration described as substitution rather than addition?
Give me a hint
Compare the ring hydrogen before and after reaction.
Compare my reasoning
- A ring hydrogen is replaced by –NO₂.
- The ring framework is retained.
- The aromatic π system is restored in the product.
It is substitution because –NO₂ replaces a ring H and the aromatic ring is restored, rather than adding across a ring bond.
Look for these in your work
- Group replacement stated
- Ring retained
- Aromaticity linked
A learner uses concentrated nitric acid at 120°C and predicts nitrobenzene. What syllabus condition must be corrected?
Give me a hint
Compare the stated temperature with the official range.
Compare my reasoning
- The nitrating mixture includes concentrated H₂SO₄ as well as HNO₃.
- The specified temperature is 25–60°C.
- The proposed 120°C is above this range.
Use concentrated HNO₃ and concentrated H₂SO₄ at 25–60°C; 120°C does not meet the stated condition.
Look for these in your work
- Both acids included
- Temperature range stated
- Mismatch identified
Common mistakes
- Using dilute nitric acid
- Omitting the temperature range
- Writing nitrobenzene as an addition product
- Confusing nitro, –NO₂, with nitrite, –ONO
What can you explain now?
Which temperature range is specified for nitrating benzene?
Compare with the explanation
25–60°C
The syllabus specifies a temperature between 25°C and 60°C.
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Make it stick
What reagents, temperature and product define nitration of an aromatic ring?
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.