See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

Concept: Fractional distillation separates compounds based on differences in boiling points. Structural isomers have different boiling points and are separated as distinct fractions, whereas enantiomers (non-superimposable mirror images) have identical boiling points and cannot be separated by fractional distillation. Step 1: Identify the starting material. The zigzag structure shown is n-hexane: CH3CH2CH2CH2CH2CH3. Step 2: Identify all unique mono-chlorination positions in n-hexane. Due to the symmetry of n-hexane, there are three unique carbon positions: - C1 (equivalent to C6): gives 1-chlorohexane - C2 (equivalent to C5): gives 2-chlorohexane - C3 (equivalent to C4): gives 3-chlorohexane Step 3: Check for chirality (stereoisomers): - 1-chlorohexane: no chiral center, one compound. - 2-chlorohexane: C2 is a chiral center (attached to CH3, C2H5 chain remainder, Cl, H) -> exists as R and S enantiomers. - 3-chlorohexane: C3 is a chiral center (attached to CH2CH3 on each side differently... actually C3 has: CH2CH2CH3, CH2CH3, Cl, H) -> exists as R and S enantiomers. Step 4: Determine fractions upon fractional distillation. Enantiomers have identical boiling points and co-distill as one fraction. Structural isomers have different boiling points and separate. - Fraction 1: 1-chlorohexane (bp ~135°C) - Fraction 2: 2-chlorohexane (R+S mixture, bp ~122°C) - Fraction 3: 3-chlorohexane (R+S mixture, bp ~123°C) Step 5: Count fractions. There are 3 distinct structural isomers, each with a different boiling point, giving 3 fractions. Enantiomeric pairs within each structural isomer distill together. Why other options fail: - (a) 2: Undercounts; there are three structurally distinct chlorohexanes. - (c) 4 and (d) 5: Overcounts; enantiomers cannot be separated by fractional distillation, so R and S forms of 2-chlorohexane and 3-chlorohexane each give only one fraction respectively. Therefore, the correct answer is B.