Skip to Content

Weirdly Polar

AllF
This is a neat little structure, and it’s truly a pain to synthesize (12 steps from myo-inositol). But it now seems to hold the record as the most polar aliphatic compound ever measured, and well it might. David O’Hagan of St. Andrews reported it at the ACS meeting in Denver – one side of that molecule is full of electronegative fluorines, and the other side has what’s left. In bulk, this would be a very unusual solvent to play around with in chromatography and the like, but I don’t think we’re going to see any four-liter jugs of around the lab any time soon.
Update: annoyingly for my speculations, the compound appears to be a solid. Maybe the smaller-ring analogs?

20 comments on “Weirdly Polar”

  1. nitrosonium says:

    boiling point??

  2. Anonymous says:

    “the all-cis isomer has twice the strain energy as any other isomer”
    No kidding.

  3. Anonymous says:

    So many questions and so little access:
    Article describes it as crystalline. Melting Point?
    Solubility in not-too-polar organic solvents (THF, octanol)?
    Conductivity either pure or in mixtures?
    Is it really a chair or do the axial fluorine dipole-dipole repulsions distort it significantly?

  4. Anonymous says:

    Pardon my ignorance, but what’s stopping three of the ‘up’ fluorines from spontaneously switching to the ‘down’ position?

  5. Ann O Mouse says:

    @4
    If you mean while maintaining the chair conformation, then because that would involve breaking and then reforming three C-F bonds and three C-H bonds(there are three C-H bonds in those positions now, just not drawn by convention), and that would not happen spontaneously. If you mean with just a change in conformation (shape change, no bonds broken), then that would no longer be a chair conformation and likely much higher in energy.
    And yes, you are most certainly pardoned. I’m sure there are a few chemists rolling their eyes now and talking about chemical illiteracy. My philosophy has always been “light a candle”. Hope this explanation is clear.

  6. Anonymous says:

    @5 Thanks. I’m aware that there are hydrogens not drawn, but can’t they rotate with the fluorine without actually breaking any bonds? It seems like this would require some energy, but I have no idea if thermal energy is enough.
    FWIW, my only chemistry education was from high school.

  7. Ann O Mouse says:

    @6 Because of the constraints of maintaining proper bond angles, in this case including the bonds within the rings and also keeping tetrahedral carbon, the rotation you describe would change the conformation from the usually lowest energy “chair” conformation drawn to a boat, twist boat, or something else. These are usually (not always) higher in energy. Since a molecule will generally adopt the lowest energy conformation(s), flipping to something other than a chair is not likely. An old-fashioned set of molecular models would help you visualize this. I’m not sure how they assigned the conformation (NMR probably) or if they did the kind of studies necessary to establish the barrier to adopting another conformation. Probably the high dipole moment suggests a lot about conformation. Solvent effects might be significant for an organic compound with such a high dipole moment. Anyway, hope this helps, and way to go for remembering High School Chemistry.

  8. JC says:

    The fluorine version of Lindane.

  9. gippgig says:

    The cyclopropane, cyclobutane, & cyclopentane versions should be equally polar. Have any of them been made?

  10. Anonymous says:

    It’s always nice to have new solvent options for those impossible to separate mixtures! What a fun molecule!

  11. ADR says:

    Paper doesn’t seem to be out yet. Looking forward to that for sure. It’s described as crystalline, so why the talk about it being a new solvent?

  12. tangent says:

    Yeah, looks like a termite killer all right.
    Of course, that’s why I flinched at sucralose too, and people apparently eat the stuff.
    (Has anyone made ‘fluorosucralose’?)

  13. Sofia says:

    @4,6
    aside from the eloquent explanation given by @5,7 – consider that if it did manage to acquire enough energy to undergo a ring flip, that it would end up in virtually the same conformation since the equatorial positions would become axial and the axial become equatorial.
    I think @3 ‘s thought about F-F axial repulsion is more interesting though. Neutral, organofluorine is pretty small – but is still larger than hydrogen – though I would expect the high charge density to violently repulse one another. I’m not experienced with impartially fluorinated molecules, but I too am curious about what the distortion looks like and how much that contributes to the observed polarity.

  14. Anonymous says:

    Sticky lubricant???

  15. Anonymous says:

    @9 “The cyclopropane, cyclobutane, & cyclopentane versions should be equally polar. Have any of them been made?”
    I imagine the bond strain would be too much for those

  16. drug_hunter says:

    Was anyone at his talk – does he experimentally know whether it is in the chair or twist-boat conformation? Wouldn’t be hard to run a calculation, but maybe it would give the wrong answer, and that might make Derek go berzerk again.

  17. Biorganic Chemist says:

    I’d love to know the activation barrier to a chair flip (C+EN indicates a chair conformation). This is going to be a very interesting molecule for the understanding of stereoelectronic effects. I wonder how large the difference in 1JCH is for the axial versus equatorial C-H bonds. Looking forward to reading this work!

  18. cookingwithsolvents says:

    the trifluoro all-cis version (w/ 3 F’s) might 1)still be liquid and 2)be almost as polar….and 3)might be easier to make (hydrogenate 1,3,5 F3 C6H3, right?)

  19. Zemyla says:

    Why wouldn’t it be solid? A compound that massively polar probably exhibits huge amounts of self-attraction, leading to exceptionally high melting and boiling points.

Comments are closed.