Question

If there is no rotation of plane-polarized light by a compound in a specific solvent, thought to be chiral, it may mean that:
A. The compound may be a racemic mixture
B. The compound is certainly a chiral
C. The compound is certainly meso
D. There is no compound in the solvent

Answer 1

We can have different types of compounds based on the spatial arrangement of atoms or groups namely chiral compounds and achiral compounds.We know that a chiral centre imparts unique characteristics to a molecule that can be used to deduce its nature.

Step by step answer: In organic chemistry, we have seen how important a structure is for properties and reactions of a molecule. Here, we will look at the stereochemistry of a compound. In stereochemistry, we look at the spatial arrangement of atoms or groups.
A carbon atom to which four different atoms or groups are attached is known to us as a chiral centre and usually gives rise to the property of chirality in a molecule but not always. At times, we can have a molecule that is achiral even if it has a chiral centre(s) present in it; such compounds are called meso compounds. We can further understand these by taking into account the superimposability to the mirror images. In case of chiral compounds, we can see that the mirror image is not superimposable and here we get a pair of enantiomers but in case of achiral compounds, we will find that the mirror images are identical. If we take a mixture containing two enantiomers of a compound in equal amounts, we call it to be a racemic mixture.
We know that chirality is also associated with optical activity of a compound or in other words we can say that it has been established that chiral compounds rotate the plane polarized light. This rotation is of great significance as we can use this to identify, classify or even quantify a given unknown compound.
Now, let’s have a look at the given situation in which a compound is thought to be chiral that indicates that it has a chiral centre but yet it is not optically active which means that it is achiral. So, based on our discussion and given situation, we can infer that the given compound is achiral but contains chiral centres and thus can be classified to be a meso compound.

Hence, the correct option is C.

Note: We have to keep in mind that presence of a chiral centre does not necessarily mean that the compound would also be chiral and optically active. There may be the presence of a chiral centre but may not lead to the optical isomerism.