Question

All the following molecules contain more than one ring except:

• A. Cholesterol
• B. Sucrose
• C. Glucose
• D. Progesterone

Hint:

All steroid molecules (like cholesterol, progesterone, testosterone, and estrogen) contain the characteristic four-ring steroid nucleus.
Disaccharides like sucrose always contain two rings.
Monosaccharides like glucose contain only a single ring.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Organic and biomolecules are classified structurally based on the presence, number, and arrangement of rings within their chemical frameworks.
Monocyclic compounds contain a single ring, while polycyclic or oligocyclic compounds contain multiple rings.

Step 2: Detailed Explanation:
Let us analyze the chemical structures of the listed molecules:
- (A) Cholesterol: A steroid molecule containing a core cyclopentanoperhydrophenanthrene structure.
This structure consists of four fused rings (three six-membered rings and one five-membered ring). Thus, (A) contains more than one ring.
- (B) Sucrose: A disaccharide composed of one glucose unit and one fructose unit.
Its structure contains two rings (a six-membered pyranose ring from glucose and a five-membered furanose ring from fructose) connected by an \( \alpha \)-1,2-glycosidic bond. Thus, (B) contains more than one ring.
- (C) Glucose: A monosaccharide (hexose sugar).
In its stable aqueous form, it exists as a cyclic hemiacetal containing a single six-membered pyranose ring.
Thus, glucose is a monocyclic molecule and does not contain more than one ring, making it the correct exception.
- (D) Progesterone: A steroid hormone that share the same steroid core as cholesterol.
It contains four fused rings. Thus, (D) contains more than one ring.
Therefore, Glucose is the only molecule containing a single ring.

Step 3: Final Answer:
Glucose contains only a single pyranose ring, making it the correct exception.