Question

What is the order of the stability of the isomer? Explain.

Answer 1

A chair conformation is an arrangement of cyclohexane in space as to minimize (i) ring, (ii) torsional, and (iii) transannular strain.

Substituents of carbons in the chair confirmation can exist in an axial or equatorial orientation. The latter is more stable (and energetically favorable) than the former.

In the preceding representation, the left chair's substituents are in the axial position and the right chair's substituents are in the equatorial position.

Hence, with the preceding knowledge that in most cases equatorial positions minimize strain and hence are lower energy (and consequently higher in stability), we can say,

`"D"<"C"<"B"<"A"`

To explain the disparity between `"C"` and `"B"`, we need to understand larger substituents have larger steric interactions with other substituents in the axial position. Hence, the ether group will be less stable than the alcohol group in the axial position.