Question

TheO-H hydrogen in acetic acid is more acidic than anyhydrogens. Explain this result using resonance structures.

Short answer

OH hydrogen is resonance stabilized.

Step-by-step solution

Acidic hydrogen

The hydrogen which can be more easily released from a molecule is more acidic than the one which is difficult to remove.

Resonating structure of acetic acid

Three resonating structures are possible for acetic acid:

Resonating structures

Reason for more acidic nature of OH hydrogen in acetic acid

From resonating structure, it can be seen that CH hydrogen is not stabilized by resonance. The carbocation generated will be unstable, and hence this hydrogen is hard to remove.

The hydrogen in OH is resonance stabilized. Therefore, it will generate a stable carbocation, and this hydrogen can be easily removed from the molecule. This hydrogen is, therefore, more acidic than acetic acid.