All-cis 1,2,3,4,5,6-hexafluorocyclohexane is a facially polarized cyclohexane

• Published in: Nature chemistry 2015-06, Vol.7 (6), p.483-488
• Main Authors: Keddie, Neil S., Slawin, Alexandra M. Z., Lebl, Tomas, Philp, Douglas, O'Hagan, David
• Format: Article
• Language: English
• Subjects: 119/118; 140/131; 639/638/403/935; Analytical Chemistry; Biochemistry; Chemistry; Chemistry/Food Science; Inorganic Chemistry; Organic Chemistry; Physical Chemistry
• ISSN: 1755-4330; 1755-4349
• DOI: 10.1038/nchem.2232

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 F ax ···F ax distances (∼2.77 Å) are longer than the vicinal F ax ···F eq­ 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. The highest-energy stereoisomer of 1,2,3,4,5,6-hexafluorocyclohexane, with all the fluorines ‘up’, has been prepared in a 12-step protocol. The molecule adopts a chair conformation with three triaxial C–F bonds on one face generating a polarized ring. In the solid state the molecules pack in an orientation consistent with electrostatic ordering.