Which of the following will not show geometrical isomerism?

Options

A. `Ph-N=N-Ph`
B. `2,4-` Dinitro phenyl hydrazone of acetone
C. Oxime of formaldehyde
D. Cyclohexan `1,2-` diol

Explanation

To determine which of the given compounds will not show geometrical isomerism, we will analyze each option one by one.

### Step-by-step Solution:

1. **Identify the first compound: pH=N-pH (Phenyl double bond to Phenyl)**
- This compound has a double bond between two phenyl groups.
- Since each phenyl group can be on the same side (cis) or opposite sides (trans) of the double bond, this compound can show geometrical isomerism.
- **Conclusion:** This compound shows geometrical isomerism.

2. **Identify the second compound: 2,4-dinitrophenylhydrazone of acetone**
- The structure of this compound includes a double bond between the carbon of the acetone and the nitrogen of the hydrazone.
- In this case, the two groups attached to the nitrogen are both nitro groups (2,4-dinitro), and the other side has a methyl group from acetone.
- Since there are two identical groups (nitro groups) across the double bond, this compound cannot show geometrical isomerism.
- **Conclusion:** This compound does not show geometrical isomerism.

3. **Identify the third compound: Oxime of formaldehyde**
- The oxime of formaldehyde has the structure R1C=N-OH, where R1 is a hydrogen atom.
- Here, both groups across the double bond (C=N) are the same (both are hydrogen atoms).
- Since there are two identical groups (hydrogens) across the double bond, this compound cannot show geometrical isomerism.
- **Conclusion:** This compound does not show geometrical isomerism.

4. **Identify the fourth compound: Cyclohexane 1,2-Diol**
- The structure of Cyclohexane 1,2-Diol has two hydroxyl (OH) groups attached to adjacent carbon atoms in a cyclic structure.
- This compound can exist in two forms: one where both OH groups are on the same side (cis) and one where they are on opposite sides (trans).
- Therefore, this compound can show geometrical isomerism.
- **Conclusion:** This compound shows geometrical isomerism.

### Final Answer:
The compounds that do not show geometrical isomerism are:
- **Option B: 2,4-dinitrophenylhydrazone of acetone**
- **Option C: Oxime of formaldehyde**