AQA · A-Level · Chemistry
Course version: 7405 · Version from Sept 2016
Nitration is an important step in synthesis, including the manufacture of…
Full specification wording
Electrophilic substitution (A-level only): Nitration is an important step in synthesis, including the manufacture of explosives and formation of amines.
Nitration puts an -NO₂ group onto the ring using a mixture of concentrated nitric acid and concentrated sulfuric acid, warmed to about 50 °C. The sulfuric acid is the catalyst: it protonates the…
Checked against the AQA 7405 specification (opens in a new tab) on .
- Point 2 of 4
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Nitration puts an -NO₂ group onto the ring using a mixture of concentrated nitric acid and concentrated sulfuric acid, warmed to about 50 °C. The sulfuric acid is the catalyst: it protonates the nitric acid so that the nitronium ion NO₂⁺ can form, and it is regenerated at the end. Temperature control matters, because above about 50 °C a second nitro group is substituted and dinitrobenzene forms. The product is the gateway to two important families. Reducing the nitro group, with tin and concentrated hydrochloric acid and then excess sodium hydroxide, gives an aromatic amine such as phenylamine, the starting point of azo dyes. Repeated nitration of methylbenzene gives TNT, an explosive.
What earns the marks
- Concentrated nitric acid and concentrated sulfuric acid as the reagents.
- A temperature of about 50 °C, kept low to prevent further substitution.
- Reduction of the nitro group using tin and concentrated hydrochloric acid.
- Adding excess sodium hydroxide to release the free amine from its salt.
- Naming a use, such as dye manufacture from the amine or an explosive from repeated nitration.
Common mistakes and how to put them right
Using dilute nitric or sulfuric acid.
Writing sulfuric acid into the overall equation as a reactant that is consumed.
Stopping the reduction at the ammonium salt and omitting the sodium hydroxide stage.
Giving phenylamine as the direct product of nitration.
Exam tips
- State the temperature and say why: 'about 50 °C, to avoid further substitution' is worth more than '50 °C'.
- Use [H] in reduction equations and balance the hydrogens; nitrobenzene to phenylamine takes 6[H] and gives 2H₂O.
Try the lesson
The start of the Electrophilic substitution (A-level only): Nitration is an important step in synthesis, including the manufacture of explosives and formation of amines. lesson, made from checked teaching notes for this specification point.
Have a go first
The nitration of benzene is a crucial industrial reaction. Which of the following are two major applications of the products formed by the nitration of benzene rings?
Listen
Nitration puts an -NO₂ group onto the ring using a mixture of concentrated nitric acid and concentrated sulfuric acid, warmed to about 50 °C. The sulfuric acid is the catalyst: it protonates the nitric acid so that the nitronium ion NO₂⁺ can form, and it is regenerated at the end. Temperature control matters, because above about 50 °C a second nitro group is substituted and dinitrobenzene forms. The product is the gateway to two important families. Reducing the nitro group, with tin and concentrated hydrochloric acid and then excess sodium hydroxide, gives an aromatic amine such as phenylamine, the starting point of azo dyes. Repeated nitration of methylbenzene gives TNT, an explosive. A strong answer earns marks for these points. concentrated nitric acid and concentrated sulfuric acid as the reagents. a temperature of about 50 °C, kept low to prevent further substitution. reduction of the nitro group using tin and concentrated hydrochloric acid. adding excess sodium hydroxide to release the free amine from its salt. Exam tip: State the temperature and say why: 'about 50 °C, to avoid further substitution' is worth more than '50 °C'.
Key words
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nitration conditions
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nitronium ion
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temperature control
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reduction to amines
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See every definition
- nitration conditions
- A mixture of concentrated nitric acid and concentrated sulfuric acid, warmed to about 50 °C, with the sulfuric acid acting as the catalyst.
- nitronium ion
- The species NO₂⁺ that forms when the sulfuric acid protonates the nitric acid.
- temperature control
- Keeping the temperature at about 50 °C, because above this a second nitro group is substituted and dinitrobenzene forms.
- reduction to amines
- Reducing the nitro group with tin and concentrated hydrochloric acid and then excess sodium hydroxide gives an aromatic amine such as phenylamine.
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