Stereoisomerism via chiral centers in alkanes

Steps:

• Draw structural formulas for each compound to identify functional groups and carbon atoms.
• Check for geometric isomerism in alkenes (cis-trans due to double bond) or optical isomerism in alkanes (chiral carbon with four different substituents).
• Evaluate if any carbon has restricted rotation or asymmetry.
• Select the compound with a valid stereoisomer type.

Why C is correct:

• 1,2-Dichloropropane (CH₃-CHCl-CH₂Cl) has a chiral center at C2 with four different groups (CH₃, Cl, H, CH₂Cl), allowing optical isomers.

Why the others are wrong:

• A. 1,3-Dichloropropene (ClCH=CH-CH₂Cl) has a double bond but substituents do not enable cis-trans isomerism due to identical hydrogens on one carbon.
• B. 2,3-Dichloropropene (CH₂=CCl-CH₂Cl) is a terminal alkene with two hydrogens on C1, preventing geometric isomerism; no chiral center.
• D. 1,3-Dichloropropane (ClCH₂-CH₂-CH₂Cl) is a symmetric alkane with no chiral centers or double bonds.

Final answer: C