All-cis 1,2,3,4,5,6-hexafluorocyclohexane is a facially polarised cyclohexane
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The highest-energy stereoisomer of 1,2,3,4,5,6-hexafluorocyclohexane, in which all of the fluorines are ‘up’, is prepared in a 12-step protocol. The molecule adopts a classic chair conformation with alternate C–F bonds aligned triaxially, clustering three highly electronegative fluorine atoms in close proximity. This generates a cyclohexane with a high molecular dipole (μ = 6.2 D), unusual in an otherwise aliphatic compound. X-ray analysis indicates that the intramolecular Fax···Fax distances (∼2.77 Å) are longer than the vicinal Fax···Feq distances (∼2.73 Å) suggesting a tension stabilizing the chair conformation. In the solid state the molecules pack in an orientation consistent with electrostatic ordering. Our synthesis of this highest-energy isomer demonstrates the properties that accompany the placement of axial fluorines on a cyclohexane and the unusual property of a facially polarized ring in organic chemistry. Derivatives have potential as new motifs for the design of functional organic molecules or for applications in supramolecular chemistry design.
Keddie , N S , Slawin , A M Z , Lebl , T , Philp , D & O'Hagan , D 2015 , ' All-cis 1,2,3,4,5,6-hexafluorocyclohexane is a facially polarised cyclohexane ' Nature Chemistry , vol 7 , no. 6 , pp. 483-488 . DOI: 10.1038/nchem.2232
© 2015 the Author(s). This work is made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at http://dx.doi.org/10.1038/nchem.2232
This work was generously supported by the Engineering and Physical Sciences Research Council (EPSRC) and the European Research Council (ERC).
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