Q.62. - Organic Chemistry

Question

Question: Draw the three constitutional isomers having molecular formula ${\mathit{C}}_{\mathbf{7}}{\mathit{H}}_{\mathbf{14}}$ that contain a five-membered ring and two methyl groups as substituents. For each constitutional isomer that can have cis and trans isomers, draw the two stereoisomers.

Step-by-Step Solution

Answer

Answer

Constitutional isomers 

Cis and Trans isomers

Step 1: Molecular formula

The molecular formula of a compound describes the number of atoms of each kind of element present. 

One or more compounds with different structures can have the same molecular formula.

Step 2: Constitutional isomerism

Compounds with the same molecular formula may differ in terms of connectivities and bonding between their atoms.

Such varied connectivities for the same molecular formula give rise to constitutional isomers for the given molecular formula.

Step 3: Draw the constitutional isomers for the given molecular formula

Draw a five-membered ring and two methyl groups in each of the three isomeric structures. To make three isomeric structures, the relative positions of the two methyl groups on all three five-membered rings must be different. 

Hence, the three isomeric structures are:

Constitutional isomers 

Out of the three constitutional isomers, the second and third structures, i.e., 1,2-dimethylcyclopentane and 1,3-dimethylcyclopentane, can have cis and trans isomers. Hence, the two cis and trans isomers are:

Cis and trans isomers