Which of the following molecules cannot show geometric isomerism ?

Options

A. `CH_(3)CH=NOH`
B. `(CH_(3))_(2)C=NOH`
C. HO-N=N-OH
D.

Answer

To determine which of the given molecules cannot show geometric isomerism, we need to analyze each molecule based on the criteria for geometric isomerism. Geometric isomerism, also known as cis-trans isomerism, typically occurs in compounds with a double bond where different atoms or groups are attached to the carbon atoms involved in the double bond.

### Step-by-Step Solution:

1. **Identify the Molecules**: We have four molecules to analyze. Let's denote them as A, B, C, and D.

2. **Check for Double Bonds**: Geometric isomerism can only occur in molecules with at least one double bond (C=C or C=N, etc.).

3. **Analyze Molecule A**:
- Structure: C=N, OH, H, CH3
- Here, we have a double bond between carbon and nitrogen. The groups attached to the carbon are OH, H, and CH3, which are different.
- **Conclusion**: Molecule A can show geometric isomerism.

4. **Analyze Molecule B**:
- Structure: C=N, OH, CH3, CH3
- This molecule also has a double bond between carbon and nitrogen, but both groups attached to the carbon are methyl groups (CH3).
- **Conclusion**: Molecule B cannot show geometric isomerism because it has identical groups attached.

5. **Analyze Molecule C**:
- Structure: N=N, OH, OH
- This molecule has a double bond between two nitrogen atoms, but both groups attached to one of the nitrogen atoms are hydroxyl groups (OH).
- **Conclusion**: Molecule C cannot show geometric isomerism due to identical groups.

6. **Analyze Molecule D**:
- Structure: A three-membered carbon ring with Cl, Cl.
- This molecule does not have a double bond, which is essential for geometric isomerism.
- **Conclusion**: Molecule D cannot show geometric isomerism because it lacks a double bond.

### Final Answer:
Molecules B, C, and D cannot show geometric isomerism.