2‐chlorooxane conformers

Out of these two, which one is more stable? I'm unable to imagine the orientation of the lone pairs of O and ABMO of C and Cl bond.

Any tips to tackle these kind of problems?

  • $\begingroup$ Try writing the lone pairs of the two heteroatoms as if they were attached to the atoms by bonds, in a tetrahedral geometry. What structure minimizes LP-LP interaction? :) $\endgroup$ – The_Vinz Aug 17 '19 at 9:28
  • $\begingroup$ @The_Vinz Based on your idea, I would say Cl in axial position is favorable. I also want to look at it another way. Can we consider the pi type overlap between lone pair of O and sigma asterisk bond of C and Cl? $\endgroup$ – user_9 Aug 17 '19 at 9:32
  • 2
    $\begingroup$ Yep, the answer is that: chlorine in axial position minimizes the so-called 1-3 diaxial interaction between the lone pairs, and is thus more stable (from a substantially qualitative AM1 calculation, around 15 kJ/mol lower in energy). As to the molecular orbitals, I confess that personally I couldn't extimate that interaction "on paper" $\endgroup$ – The_Vinz Aug 17 '19 at 9:43
  • 4
    $\begingroup$ Search for "anomeric effect", you will probably find a number of websites explaining this in some detail. $\endgroup$ – orthocresol Aug 17 '19 at 14:00

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