Draw the more stable chair conformation of trans-1-tert-butyl-3-methylcyclohexane. By how much is it favored?

Question

TestHub · Accepted Answer

Draw the two possible chair conformations and calculate the strain energy in each :

structure

Conformer I (t-Bu equatorial, $C H_{3}$ axial) : strain = 2 × 3.8 = 7.6 kJ/mol (two 1,3-diaxial $C H_{3} \leftrightarrow H$ interactions).

Conformer II (t-Bu axial, $C H_{3}$ equatorial) : strain = 2 × 11.4 = 22.8 kJ/mol (two 1,3-diaxial t-Bu↔H interactions).

Conformer I, with the large tert-butyl group equatorial, is the more stable conformation; it is favored by 22.8 - 7.6 = 15.2 kJ/mol.

Chemistry - STEREO ISOMERISM Question with Solution | TestHub