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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3st160

A-values (kJ/mol): tert-butyl 20.0, methyl 7.3, chlorine 2.2. Assume additivity of A-values and ignore other interactions. Select the correct statements.

  1. AFor cis-1-chloro-3-methylcyclohexane the diequatorial chair is more stable than the diaxial chair by 9.5 kJ/mol
  2. BFor trans-1-tert-butyl-3-methylcyclohexane the more stable chair has tert-butyl equatorial and methyl axial, by 12.7 kJ/mol
  3. CFor cis-1-chloro-4-methylcyclohexane the more stable chair has methyl equatorial and chlorine axial, by 5.1 kJ/mol
  4. DFor trans-1-chloro-3-methylcyclohexane the more stable chair has chlorine equatorial and methyl axial

Answer: A, B, C

cis-1,3: diaxial costs 7.3 + 2.2 = 9.5, so A is true. trans-1,3 is (ax,eq): axial methyl costs 7.3 versus 20.0 for axial tert-butyl, difference 12.7, so B is true. cis-1,4 is (ax,eq): axial chlorine (2.2) is cheaper than axial methyl (7.3), difference 5.1, so C is true. In trans-1-chloro-3-methyl the cheaper axial group is chlorine, so the stable chair has methyl equatorial and chlorine axial; D is false.
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