Q11 · CSIR NET Chemistry, December 2013
Paper: CSIR NET December 2013 · Subject: Organic Chemistry · Chapter: General Organic Chemistry · Topic: General Organic Chemistry – General · Marks: 2 · Difficulty: Medium
Consider the following statements about cis- and trans-decalins (A) cis-isomer is more stable than trans-isomer (B) trans-isomer is more stable than cis-isomer (C) trans-isomer undergoes ring-flip (D) cis-isomer undergoes ring-flip The correct statements among the above are
(a)B and D
(b)A and C
(c)A and D
(d)B and C
Answer
Answer (as printed): A
Explanation
• Trans decalin is more stable than cis decalin by about 2.7kcal/mol. • The rigid conformation of trans decalin prohibits ring flipping. Else, it would result in highly strained system with one ring attached to other by two axial bond. • Cis decalin exists as an equilibrium between two enantiomeric chair conformation and flip into one other.
Explanation as extracted from the printed page; notation may be imperfect.
Study loop for General Organic Chemistry