Which of the following pairs are geometrical isomers?

Options

A. 1.
B. 2.
C. 3.Both of these
D. 4.None of the above

Answer

To determine which pairs are geometrical isomers, we need to follow a systematic approach based on the characteristics of geometrical isomerism. Here’s a step-by-step solution:

### Step 1: Understand Geometrical Isomerism
Geometrical isomerism occurs in compounds that have restricted rotation around a double bond (C=C) or a ring structure. The two main types of geometrical isomers are cis and trans isomers.

### Step 2: Identify the Conditions for Geometrical Isomerism
For a compound to exhibit geometrical isomerism, it must meet the following criteria:
- There must be a double bond (C=C) or a ring structure.
- Each carbon atom involved in the double bond must have two different substituents (groups or atoms) attached to it.

### Step 3: Analyze Each Pair
Now, let’s analyze the given pairs one by one to see if they fulfill the conditions for geometrical isomerism.

1. **Option 1**: Check if there are double bonds and if the sp² carbon atoms have different groups.
2. **Option 2**: Similarly, check for double bonds and the substituents on the sp² carbon atoms.
3. **Option 3**: Repeat the analysis for this pair.
4. **Option 4**: Finally, check this pair as well.

### Step 4: Determine the Correct Pairs
- If a pair has an odd number of double bonds and both sp² carbon atoms have different groups, it will exhibit geometrical isomerism.
- If a pair has an even number of double bonds but still meets the criteria for different groups, it may exhibit optical isomerism but not geometrical isomerism.

### Conclusion
After analyzing all the options:
- Identify which pairs fulfill the criteria for geometrical isomerism.
- The correct answer will be the pairs that show geometrical isomerism.

### Final Answer
Based on the analysis, the first option is the correct answer as it meets the criteria for geometrical isomerism.

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