Tautomerism is not exhibited by :

Options

A.
B.
C.
D.

Answer

To determine which compound does not exhibit tautomerism, we need to understand what tautomerism is and the structural requirements for it to occur.

### Step-by-Step Solution:

1. **Define Tautomerism**: Tautomerism is a type of isomerism where isomers (tautomers) can readily interconvert by the movement of a proton and a double bond. This typically involves keto-enol tautomerism, where a ketone can convert to its corresponding enol form.

2. **Identify the Compounds**: We need to analyze the given options (though not explicitly listed in the question, we assume there are several organic compounds) to see which one lacks the structural features necessary for tautomerism.

3. **Analyze Compound B**: According to the video transcript, option B is the compound that does not exhibit tautomerism. The reasoning provided indicates that in this compound, the presence of two double bonds in a cyclic structure prevents the necessary proton transfer and double bond shift required for tautomerism.

4. **Structural Constraints**: In cyclic compounds, especially six-membered rings, if there are already two double bonds, the stability and electronic configuration do not allow for the formation of a stable enol form. Thus, tautomerization cannot occur.

5. **Conclusion**: Based on the analysis, the answer is option B, as it does not allow for the structural rearrangement necessary for tautomerism.

### Final Answer:
Tautomerism is not exhibited by option B.