Q. Acidic Hydrogen is Present in:
Answer: A. Ethyne
Explanation: Acidic hydrogen means cation of Hydrogen or H+. The acidic hydrogen is directly proportional to the s-character of hybridisation.
Ethyne is an alkyne with sp hybridisation,
Ethane is an alkane with sp³ hybridisation,
Ethene is an alkene with sp² hybridisation,
And Benzene is a cyclic alkene with sp² hybridisation.
If we look at the hybridisation of Ethyne, Ethene, Benzene, and Ethane,
We will get the following s character percentage.
s character (%)
CH ≡ CH
As the highest s-character percentage can be seen in Ethyne, its electronegativity would be highest as the carbon is close to the nucleus. This results in the release of Hydrogen ions, and hence, its hydrogen atom will be most acidic.