sulphonation of benzene occurs by which mechanism?

What is sulphonation of benzene?

Sulphonation of benzene is carried out in the presence of fuming sulphuric acid and sulfur trioxide.

Sulphonation of benzene is a technique in which benzene heated with the presence of fuming sulphuric acid or sulfur trioxide, the it give benzene sulphonic acid.

lets go to know how to reaction is carried out.

When benzene is react with fuming H2SO4 sulphuric and presence of sulfur trioxide then acid then as a result benzene sulphonic acid is formed.

Due to this reaction benzene sulphonic acid is formed.

Sulphonation of benzene occurs by which mechanism?

Sulphonation of benzene occurred by three steps mechanism. and they are,

  1. Genration of electrophile.
  2. Attack electrophile on benzene ring
  3. Removal of old electrophile

Genration of electrophile

Sulphuric acid + sulfur trioxide + H3O are add. As shown in reaction.

Attack electrophile on benzene ring

When electrophile (SO3) attack the benzene ring, and leading to the formation of benzenesulfonic acid. H2SO4, sulphuric acid + sulfur trioxide and H3O both are add. You know that, oxygen has highly electronegativity, oxygen is persent in sulphuric acid pull an electron towards itself. as a result, generation of electrophile (SO3).

where,

SO3 – sulfur trioxide

H2SO4 – sulphuric acid

Benzene is react with sulfur trioxide as a result sigma complex is formed. and finely benzene sulfonic acid is formed as a final product.

Sulphonation of benzene occurs by which mechanism

Attack electrophile on benzene ring

Removel of old electrophile

Here, one sulphuric acid is remove.

This are the final result

Blance equation is equall but it’s mechanism is different.

Conclusion

In sulphonation of benzene, When benzene react with sulfur trioxide then it give benzene sulfonic acid is formed as a final product.


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