See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

Concept: Geometrical (cis-trans) isomerism in cycloalkanes arises when two or more ring carbons each bear two different substituents, preventing free rotation about the ring C-C bonds. Step 1: Identify the compound. The structure shown is 1,2-dimethylcyclohexane. Carbons 1 and 2 of the cyclohexane ring each carry one methyl group and one hydrogen, making them stereocenters with respect to the ring plane. Step 2: Determine how many geometrical isomers exist for 1,2-dimethylcyclohexane. Because both methyl-bearing carbons (C1 and C2) have two different substituents (CH3 and H), cis-trans isomerism is possible. The two geometrical isomers are: - cis-1,2-dimethylcyclohexane: both CH3 groups on the same face of the ring. - trans-1,2-dimethylcyclohexane: the two CH3 groups on opposite faces of the ring. Step 3: Count. That gives exactly 2 geometrical isomers. Step 4: Evaluate other options. - (a) 0 is wrong because geometrical isomerism clearly exists here. - (c) 3 and (d) 4 are wrong; there are only two possible geometric relationships (same side vs. opposite side) for a 1,2-disubstituted cyclohexane with identical substituents. Therefore, the correct answer is B.