Which of the following nitoalkane will not show tautomerism ?

Options

A. `CH_3CH_2CH_2CH_2NO_2`
B. `CH_3-CH-underset(CH_3)underset(|)(CH_2)-CH_2NO_2`
C. `CH_3-underset(NO_2)underset(|)(CH)-CH_2-CH_3`
D.

Answer

To determine which nitroalkane will not show tautomerism, we need to understand the concept of tautomerism and the role of alpha-hydrogens in this process.

### Step-by-Step Solution:

1. **Understanding Tautomerism**:
- Tautomerism is a type of isomerism where compounds can readily interconvert between two or more structural forms. This typically involves the migration of a hydrogen atom and a shift in the position of a double bond.
- A key requirement for a compound to exhibit tautomerism is the presence of at least one alpha-hydrogen. The alpha-hydrogen is the hydrogen atom attached to the carbon adjacent to the functional group (in this case, the nitro group -NO2).

2. **Identifying Alpha-Hydrogens**:
- For each nitroalkane option provided, we need to identify the alpha-carbon (the carbon next to the -NO2 group) and check if it has any hydrogen atoms attached to it (alpha-hydrogens).

3. **Analyzing Each Option**:
- **Option 1**:
- Structure: CH3-CH2-CH2-CH2-NO2
- The alpha-carbon (the one adjacent to -NO2) has two hydrogen atoms. Therefore, it can show tautomerism.

- **Option 2**:
- Structure: CH3-CH-CH2-CH2-NO2
- The alpha-carbon has two hydrogen atoms. Thus, it can also show tautomerism.

- **Option 3**:
- Structure: CH3-CH2-CH-CH3-NO2
- The alpha-carbon here has two hydrogen atoms. Hence, it can show tautomerism as well.

- **Option 4**:
- Structure: (CH3)3C-NO2
- The alpha-carbon (the one adjacent to -NO2) has no hydrogen atoms (it is bonded to three methyl groups). Therefore, it cannot show tautomerism.

4. **Conclusion**:
- Based on the analysis, the nitroalkane that does not have any alpha-hydrogens and thus will not show tautomerism is **Option 4**.

### Final Answer:
**Option 4** will not show tautomerism.

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