Question

1)The all-cis isomer of 1,2,3,4,5,6-hexafluorocyclohexane (for example, all six fluorines on the same face of the molecule) is one of the most polar non-ionic compounds known. explain why this is the case using chair structure to illustrate.

2) based on the above answer, what would happen to the polarity of the molecule if all the fluorines were on alternating faces (example, 1,3,5 on top face and 2,4,6 on the bottom face)?

Answer 1

1. All cis isomer of 1,2,3,4,5,6-hexafluorocyclohexane is polar molecule having dipole moment ~ 7.93 D. All the polar C-F bonds are in same direction due to which the resultant dipole vector is in the upward direct making the molecule highly polar.

2. However, the other isomer of the above molecule where all the F atoms occupy axial position is considered to be non polar since the corresponding resultant vectors are opposite to each other.