Which of the following shows configurationally isomerism ?

Options

A. Diethyldimethylammonium iodide
B. Methylethylpropylamine
C. Methylallylphenylbenzyl ammonium bromide
D. None of the above

Explanation

To determine which of the given compounds shows configurational isomerism, we need to analyze each compound for the presence of either geometrical isomerism or optical isomerism.

### Step-by-Step Solution:

1. **Understanding Configurational Isomerism**:
- Configurational isomerism refers to isomers that cannot be interconverted by simple rotation around a bond. This includes geometrical isomerism (cis/trans) and optical isomerism (enantiomers).

2. **Analyzing Compound A: Dimethyl Ammonium Iodide**:
- Structure: The compound has the formula (CH3)2N^+I^−.
- The nitrogen atom is bonded to two methyl groups (CH3) and one iodide ion (I^−).
- Since the nitrogen is not attached to four different groups (it has two identical methyl groups), it cannot exhibit optical isomerism.
- **Conclusion**: Compound A does not show configurational isomerism.

3. **Analyzing Compound B: Methyl Ethyl Propyl Amine**:
- Structure: The compound can be represented as CH3-CH2-CH(NH2)-CH3.
- The nitrogen atom is bonded to three different alkyl groups (methyl, ethyl, and propyl) and a lone pair.
- However, due to the ability of the nitrogen to flip (inversion), it does not create distinct stereoisomers.
- **Conclusion**: Compound B does not show configurational isomerism.

4. **Analyzing Compound C: Methyl Allyl Phenyl Benzyl Ammonium Bromide**:
- Structure: This compound has a nitrogen atom bonded to four different groups: methyl (CH3), allyl (C3H5), phenyl (C6H5), and benzyl (C7H7).
- Since all four groups attached to the nitrogen are different, this compound can exhibit optical isomerism.
- **Conclusion**: Compound C shows configurational isomerism.

5. **Final Answer**:
- The compound that shows configurational isomerism is **C: Methyl Allyl Phenyl Benzyl Ammonium Bromide**.