Benzene Reactions

Benzene is more susceptible to electrophilic substitution reactions than addition reactions because it loses its aromaticity during the addition reaction. Because benzene includes delocalized electrons that span over carbon atoms in the ring, it is very appealing to electrophiles and also quite stable to electrophilic replacements. In general, the electrophilic substitution reaction of benzene consists of three steps: 

1. The electrophile’s generation.

2. Formation of intermediate carbocations.

3. A proton is removed from a carbocation intermediate.

The most common benzene reactions are:-

Benzene Nitration : 

Nitrobenzene is formed when benzene interacts with concentrated nitric acid at 323-333k in the presence of intense sulphuric acid. This is referred to as benzene nitration.

The mechanism for nitration of benzene:

Step 1: Nitric acid takes a proton from sulphuric acid before dissociating to generate the nitronium ion.

Step 2: In the procedure, the nitronium ion works as an electrophile, reacting with benzene to generate the arenium ion.

Step 3: The arenium ion then loses its proton to Lewis base, resulting in the formation of nitrobenzene.

Sulfonation of Benzene: 

Sulfonation of benzene is the process of producing benzenesulfonic acid by heating benzene with fuming sulphuric acid (H2SO4 +SO3). In nature, the reaction is reversible.

The mechanism of benzene sulfonation:

Because of its increased electronegativity, the oxygen in sulfuric acid attracts an electron, resulting in the formation of an electrophile. This attacks the benzene ring and produces benzenesulfonic acid.

Halogenation of Benzene:

In the presence of Lewis acid, benzene interacts with halogens such as FeCl3, FeBr3 to create aryl halides. This process is known as benzene halogenation.

The mechanism for halogenation of benzene:

 Step 1: Because FeBr3 is a Lewis acid, it aids in the formation of electrophile bromine ions by interacting with the attacking reagent.

Step 2: In the process, the bromine ion works as an electrophile, reacting with benzene to generate arenium ion, which then transforms to bromobenzene.

CONCLUSION:

From the following article we can conclude that Benzene is more susceptible to electrophilic substitution reactions than addition reactions because it loses its aromaticity during the addition reaction.