Chapter 4, Problem 4.16YT

Interpretation Introduction

Interpretation:

The given model of half chair conformation is to be examined from different points of view, and the different types of strains are to be noted. The site of strain and the types of strain are to be indicated. Why the half-chair conformation is so high in energy is to be justified.

Concept introduction:

Cyclohexane has no ring strain because it adopts a chair conformation in which all angles are about $\text{111°}$ (close to the ideal tetrahedral angle of $109.5\text{°}$). In the half chair, the actual bond angle increases to $\text{120°}$, resulting in angle strain, and torsional strain is due to eclipsed conformation.

The half-chair conformation in a chair flip is higher in energy than the chair conformation itself due to added ring strain.