Subject: Organic Chemistry · Chapter: General Organic Chemistry · Topic: General Organic Chemistry – General · Exam: CSIR-NET DEC 2013 · 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
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.