Chapter 4, Problem 36P

Interpretation Introduction

Interpretation:Potential-energy diagram for chair−chair interconversion of methylcyclohexane should be sketched.

Concept introduction:In chair form all the $\text{C—C—C}$ bond anglesare $109.5°$ . Since this is ideal tetrahedral angle so there is no angular strain in chair form. The staggered $\text{C—H}$ bond further allows for no amount of torsional strain. There are two kinds of hydrogens in cyclohexane namely axial and equatorial indicated as follows:

  

In boat type conformation, flagpole interaction is found as illustrated below.

  

Usually, the stable conformations have bulkier groups such as isopropyl, $\mathrm{tert}-butyl$ placed equatorially while small atoms such as hydroxyl hydrogen present axial. This is stable as the bulkier group tends to have repulsive interaction with axial hydrogen via $1,3\text{-diaxial}$ interactions.