JEE Main levelSingle correct optionDifficulty 2 of 3st135
Assume the axial conformer of a monosubstituted cyclohexane lies 7.0 kJ/mol above the equatorial conformer (the A-value). Using R=8.314JK−1mol−1 and 298 K, the percentage of molecules in the equatorial conformer at equilibrium is closest to
A94.4%
B72.2%
C99.9%
D5.6%
Answer: A
K=[eq]/[ax]=e7000/(8.314×298)=e2.825=16.87. Fraction equatorial = K/(1 + K) = 94.4%. The value 5.6% is the axial fraction.