​Which of the following structures is formed with a closed chain of carbon atoms? ​

Correct option is A

The correct answer is (a) Ring structure

Explanation: A ring structure is formed when a closed chain of carbon atoms bonds together in a circular or cyclic arrangement. These structures are common in organic chemistry and are found in many types of molecules. Here’s a breakdown of what this means:

1. Cycloalkanes (Alkanes with a Ring Structure)-A cycloalkane is a type of hydrocarbon that contains a ring of carbon atoms connected by single bonds. The simplest example is cyclohexane, which consists of six carbon atoms arranged in a ring, each bonded to hydrogen atoms to satisfy the valency of carbon. Cyclohexane and other cycloalkanes can have different ring sizes, such as cyclopropane (three carbon atoms in a ring) or cyclobutane (four carbon atoms in a ring).

2. Aromatic Compounds (Ring Structures with Delocalized Electrons)-In aromatic compounds, like benzene, six carbon atoms form a planar ring with alternating single and double bonds between them, creating a stable structure due to delocalized electrons that form a resonance structure. This ring is highly stable due to aromaticity.

3. Heterocyclic Compounds-Heterocyclic compounds are cyclic compounds where the ring structure includes atoms other than carbon, such as nitrogen, oxygen, or sulfur. For example, pyridine is a six-membered ring with one nitrogen atom replacing one carbon atom in the ring.