An optically active compound having molecular formula C6H12O6 is found in two isomeric forms (A) and (B) in

nature. When (A) and (B) are dissolved in water they show the following equilibrium.
(A) Equilibrium mixture (B)
D = 1110 52.20 19.20
(i) What are such isomers called?
(ii) Can they be called enantiomers? Justify your answer.
(iii) Draw the cyclic structure of isomer (A)

To answer these questions, let's break it down step by step:

(i) What are such isomers called?

The isomers that are found in two forms in nature and show an equilibrium when dissolved in water are called anomers. Anomers are a type of stereoisomer that differ in the configuration of a specific stereocenter. In this case, the compound with the molecular formula C6H12O6 exists as two anomers, (A) and (B).

(ii) Can they be called enantiomers? Justify your answer.

Enantiomers are a specific type of stereoisomers that are non-superimposable mirror images of each other. In order for two compounds to be enantiomers, they must have the same molecular formula, the same functional groups, and differ only in their three-dimensional arrangement.

In this case, since the two isomers (A) and (B) are not described as mirror images of each other, they cannot be called enantiomers.

(iii) Draw the cyclic structure of isomer (A)

To draw the cyclic structure of isomer (A), we need to understand its molecular formula and the concept of cyclic structures for carbohydrates.

The molecular formula C6H12O6 indicates that the compound has 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms.

For isomers of this formula (C6H12O6), we can consider the possibility of a cyclic hexose (a six-carbon sugar). In this case, isomer (A) is likely to be a cyclic hexose.

To draw the cyclic structure of isomer (A), we can use Haworth projection, which is a way to represent cyclic sugars.

Since the question does not provide any specific information about the structure of isomer (A), it is not possible to draw the exact structure without additional details. However, I can provide a general overview of how a cyclic structure can be formed using the molecular formula C6H12O6:

1. Start with a straight-chain structure of a hexose, which would have 6 carbons in a row.

2. Identify a carbon atom within the chain that can potentially form a cyclic structure. This carbon is commonly referred to as the anomeric carbon.

3. Bring the anomeric carbon closer to another carbon atom in the chain, making a bond between them. This creates a ring structure.

4. Adjust the position of the OH groups on the carbons to allow for the formation of a stable cyclic structure. Pay attention to ensure the correct number of hydrogen atoms and oxygen atoms.

Note that the specific arrangement of atoms and the configuration of the OH groups will depend on the actual structure of isomer (A), which is not provided in the question.

Optical isomers are one kind of stereoisomerism. They are called enantiomers.