Q17-69E - Organic Chemistry (Mcmurry)

Question

As a rule, axial alcohols oxidize somewhat faster than equatorial alcohols. Which would you expect to oxidize faster, cis-4-tert-butylcyclohexanol or trans-4-tert-butylcyclohexanol? Draw the more stable chair conformation of each molecule.

Step-by-Step Solution

Answer

A cis-4-tert-butylcyclohexanol oxidizes faster.

Step 1: Most Chair conformation

The most stable chair conformation is the conformation in which both substituents are present at the equatorial position rather than at the axial position. The bulky group should always be present at the equatorial position.

Step 2: The more stable chair conformation of each molecule

In cis-4-tert-Butylcyclohexanol, the hydroxyl group is axial, and it is expected to oxidize faster than the trans-4-tert-Butylcyclohexanol. Remember that the bulky tert-butyl group is always present at the equatorial position in the more stable isomer.

More stable chair conformation of each molecule