Question

Number of chiral atoms in Glucose and Fructose are:
(A).4 in each
(B).3 in each
(C).4 in glucose and 3 in fructose
(D).3 in glucose and 4 in fructose

Answer 1

Hint: Glucose and fructose are isomers, i.e. they have the same chemical formula but differ in connectivity.

Complete answer:
First of all, a chiral carbon is a carbon which has four different atoms or groups of atoms attached to it. The chiral atom in a molecule makes it optically active. Glucose and fructose are structural isomers. Their molecular formula is ${C_6}{H_{12}}{O_6}$. They both have different parent functional groups. The functional group in glucose is an aldehyde, while in fructose is a ketone.
The open chain structure of glucose is:

And the open chain structure of fructose is:

A chiral carbon is always an $s{p^3}$ carbon. If we number the carbon atoms from the top in each structure, the carbon numbered 2,3,4 and 5 are chiral in glucose as they have 4 different atoms or molecules attached to them. Similarly, carbon numbered 1,3,4,5 are chiral in fructose.

Hence, the number of chiral atoms in glucose and fructose are 4 each.

Additional information:
Generally, glucose and fructose don’t exist in this open chain form. For the sake of convenience, we imagine their open chained structures. But in reality, they exist in chain forms. Glucose is a six membered ring while fructose is a five membered ring.

Note:
A student might also consider $s{p^2}$ carbon to be chiral if it has all different atoms or molecules attached to it, but only $s{p^3}$ carbons can be classified as chiral or achiral.