Page 1 of 1

Distinguish axial and equatorial

Posted: Mon Sep 19, 2011 4:04 pm
by Chem_Mod
If only the carbons of cyclohexane are given, how does one distinguish between an axial and an equatorial C-H bond? Why is it that, as the size of an alkyl substituent increases, preference for conformations with the group equatorial increases?

Re: Distinguish axial and equatorial

Posted: Mon Sep 19, 2011 4:04 pm
by Chem_Mod
The reader has the freedom to place the axial and an equitorail C-H bonds, but remember to alternate them from carbon to carbon. Usually the largest substituents will be placed in an equatorial position which represents the lowest energy sturcture, but the cyclohexane can undergo a chair flip and may exist in small quantities with a higher energy conformation. The larger the substitutient the greater the unfavorable diaxial interactions. A bulky group therefore has a preference for the equatorial position.