NEETChemistryGeneral Organic Chemistry
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): 1,2-Dimethylcyclobutane exhibits geometrical isomerism whereas 1,1-dimethylcyclobutane does not. Reason (R): For geometrical isomerism in cycloalkanes, at least two ring carbons must be sp ^3 hybridized and each must be bonded to two different atoms or groups. In the light of the above statements,
Options
- ABoth Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
- BBoth Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A).
- CAssertion (A) is true but Reason (R) is false.
- DAssertion (A) is false but Reason (R) is true.
Correct answer
A. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
Step-by-step solution
Assertion (A) is true: 1,2-Dimethylcyclobutane has two adjacent sp ^3 hybridized carbons (C-1 and C-2), each bonded to a hydrogen atom and a methyl group. Because these two carbons each have two different groups, the molecule can exist as cis and trans isomers. In contrast, 1,1-dimethylcyclobutane has two identical methyl groups on the same carbon (C-1), so it cannot show geometrical isomerism. Reason (R) is true: The necessary condition for geometrical isomerism in cycloalkanes is that at least two sp ^3 hybridize