Which of the following species will be optically active ?

Options

A.
B.
C.
D.

Explanation

To determine which of the given species are optically active, we need to understand the concept of optical activity. A compound is optically active if it can rotate the plane of polarized light, which typically occurs when the compound is chiral. Chirality means that the molecule has a non-superimposable mirror image, often due to the presence of a chiral center (usually a carbon atom bonded to four different substituents).

Let's analyze the options step by step:

### Step 1: Identify the nature of each option
1. **Geometrical Isomers (Cis and Trans)**:
- Geometrical isomers can be cis or trans forms. These isomers often have a plane of symmetry, which means they are superimposable on their mirror images. Therefore, they are not chiral and are optically inactive.

2. **Nitrogen with Four Different Substituents**:
- If a nitrogen atom is bonded to four different groups, it creates a chiral center. Chiral nitrogen can lead to optical activity, as it does not have a plane of symmetry. Thus, this species is optically active.

3. **Two Rings with Different Planes**:
- If the two rings are oriented in such a way that they are not superimposable on their mirror images (for example, due to a 90-degree twist), this can create chirality. Therefore, this compound is also optically active.

4. **Triple Bond with Geometrical Isomers**:
- Similar to the first option, if the compound exhibits geometrical isomerism (cis and trans) due to a triple bond, it likely has a plane of symmetry and is superimposable on its mirror image. Hence, it is optically inactive.

### Conclusion:
Based on the analysis:
- **Option 1**: Optically inactive (wrong option).
- **Option 2**: Optically active (correct option).
- **Option 3**: Optically active (correct option).
- **Option 4**: Optically inactive (wrong option).

Thus, the correct options that are optically active are **B and C**.

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