Which among the following compounds will shows tautomerism

Options

A. 2,2- dimethylpropanal
B. 2,2- demethyl -1- nitropropane
C. Acetyl actone
D. Benzophenone

Answer

To determine which of the given compounds shows tautomerism, we need to identify the presence of alpha-hydrogens adjacent to a functional group that can undergo tautomeric shifts. Tautomerism typically involves the migration of a hydrogen atom and a shift of a double bond.

### Step-by-Step Solution:

1. **Understanding Tautomerism:**
- Tautomerism is a type of isomerism where a compound can exist in two forms that are interconvertible, typically involving the shift of a hydrogen atom and a change in the position of a double bond.
- For a compound to exhibit tautomerism, it must have an alpha-hydrogen (a hydrogen atom attached to the carbon adjacent to the functional group).

2. **Analyzing the Options:**
- We will examine each compound provided in the options to see if they have alpha-hydrogens.

3. **Option 1: 2,2-Dimethylpropanol**
- Structure: The compound has a tertiary alcohol with no alpha-hydrogens available because the carbon attached to the hydroxyl group (OH) is surrounded by methyl groups.
- Conclusion: **Does not show tautomerism.**

4. **Option 2: 2,2-Dimethyl-1-nitropropane**
- Structure: Similar to the first option, the carbon with the nitro group does not have any alpha-hydrogens available due to the surrounding methyl groups.
- Conclusion: **Does not show tautomerism.**

5. **Option 3: Acetylacetone**
- Structure: Acetylacetone has a keto group (C=O) and two adjacent methyl groups. The carbon adjacent to the keto group has hydrogens (alpha-hydrogens).
- Mechanism: The hydrogen from the alpha-carbon can migrate to the oxygen, forming an enol form.
- Conclusion: **Shows tautomerism.**

6. **Option 4: Benzophenone**
- Structure: Benzophenone has a ketone functional group, but the adjacent carbons (from the phenyl rings) do not have any alpha-hydrogens available.
- Conclusion: **Does not show tautomerism.**

7. **Final Conclusion:**
- Among the options provided, only **Acetylacetone** shows tautomerism due to the presence of alpha-hydrogens adjacent to the functional group.

### Final Answer:
**Acetylacetone shows tautomerism.**