Q6 · CSIR-NET Chemistry, December 2017
Paper: CSIR-NET December 2017 · Subject: Organic Chemistry · Chapter: General Organic Chemistry · Topic: Conformational Analysis · Marks: 2 · Difficulty: Medium
Under review — part of this question (a structure or an option) is not clear in the source scan. 4AB is checking it against the original book; the answer shown may change.
Among the structures given below, the one that corresponds to the most stable conformation of compound $A$ is 
(a)
(b)
(c)
(d)
Answer
Under review — not yet confirmed.
Answer: A
Explanation
In the 1,3-dioxane the 2-methyl group must be equatorial (an axial 2-substituent clashes with the ring oxygens' lone pairs less than with C–H, but the anomeric position strongly prefers equatorial); the 5-hydroxyl then sits axial, where it hydrogen-bonds to the ring oxygens — structure (a).
Study loop for General Organic Chemistry