Paper 1 Q1 — Chair conformation & 1,3-diaxial strain

Conformational analysis — large groups prefer equatorial to avoid 1,3-diaxial interactions

What the examiners said

“Candidates showed awareness of minimising 1,3-diaxial interactions but some did not clearly [identify the preferred conformation]…”

Try the question (reconstruction)

In the more stable chair conformation of methylcyclohexane, the methyl group is:

Examiner report: “Candidates knew about 1,3-diaxial interactions but didn't clearly pick the equatorial conformation.”

Explore — axial vs equatorial

Flip the chair. When the methyl is axial, the 1,3-diaxial clashes (highlighted) raise the energy; equatorial avoids them.

The bigger the substituent, the stronger its preference for equatorial — 1,3-diaxial strain is the reason.

Original reconstruction inspired by the misconceptions described in the Singapore-Cambridge GCE A-Level H3 Chemistry 9813 November 2023 Examiner Report. Not the actual examination question. For classroom exploration.

Made by lookang, using Claude Fable 5. More resources: iwant2study.org