Nitration of Benzene w/ H2SO4 & HNO3 at 55°C

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In summary, the nitration of benzene using concentrated H2SO4 and HNO3 at 55 degrees celsius involves concentrated H2SO4 acting as a catalyst for the reaction. This concentrated acid serves two purposes - as an acid it catalyzes the reaction, and it also removes water from the HNO3/benzene pair, shifting the reaction equilibrium to the right. The acid does get more diluted during the process, but it is not entirely consumed. In the mechanism, sulfuric acid is regenerated, but in practice, the reaction will stop if there is not a large excess of acid. While the strict definition of a catalyst may not always apply in chemistry, it is still a useful term to describe the role of
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cyt91
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In the nitration of benzene using conc. H2SO4 and HNO3 at 55 degrees celsius, is concentrated H2SO4 a catalyst for the reaction?
 
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  • #2
This is a border case for me.

Write reaction equation.

You start with concentrated acid, does it stay concentrated?
 
  • #4
This is a little bit more complicated.

Concentrated sulfuric acid serves two purposes. First, as an acid it catalyzes the reaction. However, it also removes water from the HNO3/benzene pair, shifting reaction equilibrium to the right. In the process it gets more and more diluted and at some moment it is no longer able to catalyze the process. By definition catalyst is not consumed, obviously in this case it is not entirely true.
 
  • #5
But in the mechanism...isn't sulphuric acid regenerated? So sulphuric acid is not consumed.
 
  • #6
In the mechanism - yes. But if you run the reaction acid gets diluted, so if it wasn't in a large excess reaction will stop. There is no error in calling it a catalyst when applying simple and rigid definition of catalyst. Unfortunately, chemistry hates simple and rigid definitions, and you can be sure almost always you will find a system that doesn't fit.
 

1. What is the purpose of nitration of benzene with H2SO4 and HNO3 at 55°C?

The purpose of this reaction is to introduce a nitro group (-NO2) onto the benzene ring, creating nitrobenzene. This is an important step in the synthesis of various organic compounds, such as explosives, dyes, and pharmaceuticals.

2. How does the reaction of nitration of benzene occur?

The reaction occurs through an electrophilic aromatic substitution mechanism, where the nitronium ion (NO2+) is formed as the electrophile from the reaction of sulfuric acid and nitric acid. This electrophile then attacks the benzene ring, leading to the substitution of a hydrogen atom with a nitro group.

3. What is the role of H2SO4 in the nitration of benzene?

H2SO4 serves as a catalyst in this reaction, promoting the formation of the nitronium ion and enhancing the electrophilicity of the nitronium ion. It also helps to remove the water produced during the reaction, driving the equilibrium towards the formation of the desired product, nitrobenzene.

4. Why is the reaction temperature set at 55°C?

The reaction is typically carried out at 55°C because it is the optimal temperature for the formation of the nitronium ion. At lower temperatures, the reaction may be too slow, while at higher temperatures, there is a risk of side reactions occurring.

5. What precautions should be taken when performing the nitration of benzene?

Some precautions to take include wearing appropriate protective gear, as the reactants and products can be harmful if they come into contact with skin or eyes. It is also important to carefully control the temperature and avoid any sources of ignition, as the reaction is exothermic and can lead to a fire or explosion.

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