If there is no rotation of plane polarised light by a compound in a specific solvent, though to be chiral, it may mean that [2007]a)the compound is certainly mesob)there is no compound in the solventc)the compound may be a racemic mixtured)the compound is certainly a chiral.Correct answer is option 'A'. Can you explain this answer?

Question

Answer

Meso compound does not rotate plane polarised light. Compound which contains tetrahedral atoms with four different groups but the whole molecule is a chiral, is known as meso compound. It possesses a plane of symmetry and is optically inactive.

•One of the asymmetric carbon atoms turns the plane of polarised light to the right and other to the left and to the same extent so that the rotation due to upper half is compensated by the lower half, i.e., internally compensated, and finally there is no rotation of plane polarised light.

Answer

Meso Coz they have opposite rotation and will cancel each other so net there is no rotation!!!

Answer

Explanation:

Introduction:
In the context of this question, plane polarized light refers to light waves that oscillate in a single plane. When plane polarized light passes through a chiral compound, it undergoes a phenomenon called optical rotation. Optical rotation is the rotation of the plane of polarization of light as it passes through a chiral compound. The degree of rotation depends on the nature of the compound and the concentration of the solution.

Chirality:
Chirality refers to the property of a molecule that cannot be superimposed onto its mirror image. Chiral molecules possess a non-superimposable mirror image and exist in two enantiomeric forms - the left-handed (L) and right-handed (D) forms. Chiral compounds are optically active, meaning they have the ability to rotate the plane of polarized light.

Optically Inactive Compounds:
Some compounds that appear to be chiral may not exhibit optical activity. There are a few reasons for this:

1. The compound may be meso. A meso compound is a molecule that contains chiral centers but possesses an internal plane of symmetry. This plane of symmetry cancels out the optical activity, resulting in an optically inactive compound.

2. The compound may be a racemic mixture. A racemic mixture is a combination of equal amounts of the L and D enantiomers of a chiral compound. In a racemic mixture, the optical rotations of the two enantiomers cancel each other out, resulting in an optically inactive mixture.

Answer Explanation:
Based on the given information, if a compound in a specific solvent does not rotate plane polarized light, it may mean that the compound is meso. This is the correct answer because a meso compound possesses an internal plane of symmetry that cancels out the optical rotation, resulting in an optically inactive compound.

The other options can be ruled out:

- Option 'B' suggests that there is no compound in the solvent, which is unlikely given the information provided.
- Option 'C' suggests that the compound may be a racemic mixture. While this is a possibility, it is not the only possibility, and it cannot be concluded with certainty based on the given information.
- Option 'D' suggests that the compound is certainly chiral. However, the absence of optical rotation indicates that the compound is not chiral or that it is meso.

Conclusion:
In summary, if a compound in a specific solvent does not rotate plane polarized light, it may indicate that the compound is meso. This is because a meso compound possesses an internal plane of symmetry that cancels out the optical rotation.

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