Total number of isomers (including stereoisomers) obtain on monochlorination of methylcyclohexane is ____.
Answer: 12
Solution
Methylcyclohexane has several distinct positions for chlorination:
Total = 1 + 1 + 4 + 4 + 2 = 12 isomers
Position 1 
Position 2 
Position 3 
Position 4 
Position 5
- Methyl carbon (1 position): 1 isomer
- C-1 (ring carbon bearing methyl) (1 position): 1 isomer
- C-2 position (adjacent to methyl): 2 enantiomers (chiral center) × 2 (cis/trans to methyl) = 4 isomers
- C-3 position: 2 enantiomers × 2 (cis/trans) = 4 isomers
- C-4 position (para to methyl): 2 isomers (cis/trans, no chirality due to plane of symmetry)
Total = 1 + 1 + 4 + 4 + 2 = 12 isomers
JEE Main · 2022 · 26 Jul 2022 · Shift 2 · Integer answer