In the previous videos on Organic Chemistry, i have discussed about the 3 General Steps involved in Electrophilic Aromatic Substitution Reaction Mechanism and the Halogenation of Benzene. Do check them out if you have missed that. Today, we will look at how Nitration of Benzene proceeds via Electrophilic Substitution Mechanism.

3 Steps in Nitration of Benzene via Electrophilic Substitution Reaction Mechanism:

1: Production of the electrophile (the nitronium ion, NO₂⁺ ion) using conc. H₂SO₄ and conc. HNO₃

Conc. HNO₃ acts as a base in the presence of the stronger acid, conc. H₂SO_4.

The nitronium ion, NO₂⁺ formed is a stronger electrophile.

Equation is HNO₃ (base) + 2H₂SO₄ (acid) → NO₂⁺ (electrophile) + 2HSO₄^– + H₃O⁺

2: Formation of the carbocation intermediate from the attack of the NO₂⁺ on the benzene ring

This is the slow rate-determining step since it involves the formation of an unstable carbocation intermediate from a stable aromatic compound.

3: Expulsion of H⁺ ion from the carbocation intermediate to form the aromatic nitrobenzene and the delocalised pi (π) system is preserved i.e. benzene ring is re-formed

This is the fast step since it involves the formation of stable aromatic nitrobenzene from an unstable carbocation intermediate.

Click on the following link for Video on Nitration of Benzene via Electrophilic Aromatic Substitution Reaction Mechanism.

H2 Chemistry Video on Nitration of Benzene via Electrophilic Aromatic Substitution Reaction Mechanism

Length of video: 4.25 minutes

For those taking the Singapore’s JC GCE A-Level H2 Chemistry Examination, it is important for you to be able to state the Reagents and Conditions involved in Nitration of Benzene, which are:

• Reagent: Mixture of conc. HNO₃ and conc. H₂SO₄ (Nitration Mixture)
• Conditions: Heat under reflux at 55 degree Celsius

If the temperature rises above 55 degree Celsius, further reaction is possible e.g. 1-3-dinitrobenzene will also be formed.

This is something we always emphasised in our weekly recommended JC A-Level H2 Chemistry Tuition Class.

I hope you find the content easy for your understanding and if you have any questions, leave me a comment below. Feel free to share this blog post with your friends and learn the key H2 Chemistry Concepts together.

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PS: Under related articles below, there are several blog post discussions and questions related to other Organic Chemistry concepts. You can also do a keyword search using the search box at the top right hand corner.