Question

Choose the term that correctly describes the relationship between these two sugar molecules:

(A) structural isomers

(B) cis-trans isomers

(C) enantiomers

(D) isotopes

Short answer

(A) The option “structural isomers” is true.

(B) The option “cis-trans isomers” is false.

(C) The option “enantiomers” is false.

(D) The option “isotopes”isfalse.

Step-by-step solution

Isomers

There are few molecules that can share similar molecular formulas, but they differ from one another in structural formulas. Such molecules are known as structural isomers.

Explanation of option ‘(A)’

The molecular formula for both molecules is the same that is C₃H₆O₃. However, the arrangement of the atoms and bonds is different in both molecules. A carbonyl group is present at the second carbon of the first molecule, whereas a carbonyl group is present at the first carbon of the second molecule.

Thus, both molecules have the same molecular formula but different structures.

Therefore, the given option is true.

Explanation of option ‘(B)’

The atoms in cis-trans isomers have various spatial configurations in three-dimensional space. In these isomers, trans isomers have functional groups on opposing sides of the carbon chain, whereas cis isomers have functional groups on the same side.

Here, both the molecules do not have cis-trans isomers.

Therefore, the given option is false.

Explanation of option ‘(C)’

Molecules that occur in two forms are mirror images of each other but cannot be superimposed on each other due to asymmetric carbon are referred to as enantiomers.

Here, both the molecules are not mirror images of each other.

Therefore, the given option is false.

Explanation of option ‘(D)’

Few elements have the same atomic number but can vary in atomic masses. This can occur when the proton number equalizes with the neutron number of the atom. Such elements are termed as isotopes.

Here, both are sugar molecules and not elements.

Therefore, the given option is false.