Functional group present in sulphonic acids is :
- -SO2
- [figure]
- -SO3H
- -SO4H
Answer
(3) -SO3H
Solution
Sulphonic acid: R-SO3H, e.g. benzenesulphonic acid C6H5SO3H
∵ S carries two double-bonded O atoms and one –OH ⇒ functional group -SO3H, i.e. -S(=O)2-OH
(B) has only one double-bonded O ⇒ -SO2H (sulphinic acid group)
Answer: (3)