Now we’ve introduced to you the general principles of electrophilic aromatic substitution we need to delve into the details a little more and show you some real reactions of benzene. In each case, a powerful cationic electrophile is needed to persuade the unreactive benzene to act as a nucleophile. We’ll start with nitration, the introduction of a nitro (NO₂) group. Nitration requires very powerful reagents, the most typical being a mixture of concentrated nitric and sulfuric acids.

Sulfuric acid is the stronger acid and it produces the powerful electrophile NO₂⁺ by protonating the nitric acid so that a molecule of water can leave.

The nitronium ion (NO₂⁺) is linear—it’s isoelectronic with CO₂, with an sp-hybridized nitro gen atom at the centre. It’s this nitrogen that is attacked by benzene, breaking one of the N=O bonds to avoid a five-valent nitrogen.

●Nitration converts aromatic compounds (ArH) into nitrobenzenes (ArNO₂) using NO₂– from HNO₃ + H₂SO₄.

مواضيع ذات صلة

Benzene and its reactions with electrophiles

enols and phenols

Reactions of silyl enol ethers with halogen and sulfur electrophiles

Reactions of enol ethers Hydrolysis of enol ethers

Enol and enolate reactions at oxygen: preparation of enol ethers

Silyl enol ethers

Nitrosation of enols

The Robinson annelation

Intramolecular aldol reactions

How to control aldol reactions of aldehydes

How to control aldol reactions of esters

Specifi c enol equivalents from 1,3-dicarbonyl compounds