Is a methyl group at C – 3 that is “down” assial or equatorial? Equatorial Axial Part: 1 / 3 Part 2 of 3 Is a methyl group that is ” up ” at C – 4 more stable or less stable than a methyl group that is ” up ” at C – 2 ? Less stable Same stabity More stable
Answer
Axial vs Equatorial Position of Methyl Groups on Cyclohexane
📌 Part 1 of 3: Is a methyl group at C-3 that is “down” axial or equatorial?
In a standard chair conformation of cyclohexane, the axial and equatorial positions alternate up and down around the ring. At carbon C-3:
- If the methyl group is “down”, it corresponds to an axial position.
Axial positions on odd-numbered carbons (C1, C3, C5) alternate down-up-down in the standard chair conformation.
📌 Part 2 of 3: Is a methyl group that is “up” at C-4 more stable than a methyl group that is “up” at C-2?
The stability of a methyl group on cyclohexane depends on whether it occupies the axial or equatorial position:
- At C-2, an “up” methyl group is axial.
- At C-4, an “up” methyl group is equatorial.
Equatorial positions provide more space and minimize steric hindrance, especially 1,3-diaxial interactions. Thus, a methyl group in the equatorial position is more stable.
Therefore, a methyl group that is “up” at C-4 is more stable than a methyl group that is “up” at C-2.
✅ Summary
- “Down” methyl at C-3 → Axial
- “Up” methyl at C-4 (equatorial) is more stable than “up” methyl at C-2 (axial)