Question

How many structural isomers are possible for a molecule of $C_6{H}_{12}$ composition but having at least one carbocyclic ring?

• A. Seven
• B. Six
• C. Five
• D. Three

Answer 1

Answer: (A)

(a) - Cyclohexane

It is a ring structure of six carbon atoms as the name suggests. All the carbon has 2 hydrogens each. the structure is given below



Cyclohexane

(b)- 1-Methyl cyclopentane

It is a ring structure of five carbon atoms and one methyl group is attached to the carbon atom of the ring. The structure is given below:



(c)- 1-Ethyl cyclobutane

It is a ring structure of four carbon atoms and one ethyl group is attached to the carbon atom of the ring. The structure is given below:



(d)- $1-n$ -propyl cyclopropane

It is a ring structure of three carbon atoms and at one of the carbon, a straight three carbon chain is present. The structure is given below:



(e)- 1 -isopropyl cyclopropane

It is a ring structure of three carbon atoms and at one of the carbon a straight chain of three carbon is present and the carbon of the ring is attached to the second carbon of the chain. The structure is given below:



(f)- 1,2 -Dimethyl cyclobutane

It is a ring structure of four carbon atoms and 2 methyl groups are present at the adjacent carbon atom of the ring. The structure is given below:



(g)- 1,3 -Dimethyl cyclobutane

It is a ring structure of four carbon atoms and 2 methyl groups are present at the opposite carbon atom of the ring. The structure is given below:



So the correct answer is option 'A'