Question

The compound that contains the most acidic hydrogen is

• A. H₂C=CH₂ 
• B. HC=CH
• C. H₂C=C=CH₂ 
• D. H₃C-CH₃

Hint:

In general, the more s-character in a carbon-hydrogen bond, the more acidic the hydrogen will be. Alkenes with sp-hybridized carbons are typically more acidic than those with sp2 or sp3 carbons.

Answer 1

The Correct Option is B

Step 1: Understanding the structure of compounds. 
The most acidic hydrogen is found in the compound with the weakest bond to the hydrogen atom. In this case, the hydrogen in the alkene (HC=CH) is more acidic than in the others due to the sp-hybridization of the carbon, which pulls electron density away from the hydrogen, making it more easily ionizable. 
 

Step 2: Analyzing the options. 
(A) H₂C=CH₂: Incorrect — This compound has an alkene but with less acidic hydrogen. 
(B) HC=CH: Correct — The hydrogen here is attached to a sp-hybridized carbon, making it the most acidic. 
(C) H₂C=C=CH₂: Incorrect — While this compound contains conjugation, the hydrogen here is not the most acidic. 
(D) H₃C-CH₃: Incorrect — This is an alkane, and the hydrogens are less acidic compared to alkenes. 
 

Step 3: Conclusion. 
The correct answer is (B) HC=CH as it has the most acidic hydrogen due to the sp-hybridized carbon.