Question

The electrophile involved in sulphonation of benzene is

• A. S$_2$Cl$_2$
• B. SO$_3$
• C. SO$_2$
• D. SCl$_4$

Hint:

Remember, SO$_3$ is the key electrophile in the sulphonation of benzene. It requires a catalyst, typically H$_2$SO$_4$, to facilitate the reaction.

Answer 1

The Correct Option is B

In the sulphonation of benzene, the electrophile involved is SO$_3$ (sulfur trioxide). This is part of an electrophilic aromatic substitution reaction, where SO$_3$ interacts with the electron-rich benzene ring. The reaction occurs in the presence of concentrated H$_2$SO$_4$ (sulfuric acid), which acts as a catalyst.
SO$_3$ is a highly reactive electrophile, and it readily attacks the benzene ring, replacing one of its hydrogen atoms. This leads to the formation of the sulfonated product, C$_6$H$_5$SO$_3$H, also known as benzenesulfonic acid.
On the other hand, S$_2$Cl$_2$ (disulfur dichloride), SO$_2$ (sulfur dioxide), and SCl$_4$ (sulfur tetrachloride) are not involved in the sulphonation reaction of benzene. These compounds either do not exhibit the same electrophilic reactivity or do not participate in the reaction in the same manner as SO$_3$.
Therefore, the correct electrophile in the sulphonation of benzene is SO$_3$.