A racemic mixtrue is optically inactive due to :

Options

A. The presence of plane of symmetry
B. External compensation
C. Internal compensation
D. None of these

Explanation

To solve the question regarding why a racemic mixture is optically inactive, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding Racemic Mixture**:
A racemic mixture consists of equal amounts of two enantiomers (optical isomers) of a chiral molecule. Enantiomers are molecules that are non-superimposable mirror images of each other.

2. **Optical Activity of Enantiomers**:
Each enantiomer has the ability to rotate plane-polarized light. One enantiomer will rotate the light in a clockwise direction (dextrorotatory), while the other will rotate it in an anticlockwise direction (levorotatory).

3. **Cancellation of Optical Activity**:
In a racemic mixture, since both enantiomers are present in equal amounts, the rotation caused by one enantiomer is exactly canceled out by the rotation caused by the other enantiomer. This results in no net rotation of plane-polarized light.

4. **Conclusion on Optical Inactivity**:
Because the effects of the two enantiomers cancel each other out, the racemic mixture does not exhibit any optical activity. Therefore, it is considered optically inactive.

5. **Identifying the Correct Answer**:
The reason for the optical inactivity of a racemic mixture is due to "external compensation," where the rotations from the two enantiomers compensate for each other. Thus, the correct answer to the question is "external compensation."

### Final Answer:
A racemic mixture is optically inactive due to **external compensation**.

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