| Full text | |
| Author(s): |
He, Mengfan
;
Piscelli, Bruno A.
;
Cormanich, Rodrigo A.
;
O'Hagan, David
Total Authors: 4
|
| Document type: | Journal article |
| Source: | Journal of Organic Chemistry; v. 89, n. 6, p. 10-pg., 2024-03-05. |
| Abstract | |
The conformational equilibria of selectively halogenated cyclohexanes are explored both experimentally (VT-NMR) for 1,1,4,-trifluorocyclohexane 7 and by computational analysis (M06-2X/aug-cc-pVTZ level), with the latter approach extending to a wider range of more highly fluorinated cyclohexanes. Perhaps unexpectedly, 7 ax is preferred over the 7(eq) conformation by Delta G = 1.06 kcal mol(-1), contradicting the accepted norm for substituents on cyclohexanes. The axial preference is stronger again in 1,1,3,3,4,5,5,-heptafluorocyclohexane 9 (Delta G = 2.73 kcal mol(-1)) as the CF(2 )groups further polarize the isolated CH2 hydrogens. Theoretical decomposition of electrostatic and hyperconjugative effects by natural bond orbital analysis indicated that nonclassical hydrogen bonding (NCHB) between the C-4 fluorine and the diaxial hydrogens at C-2 and C-6 in cyclohexane 7 and 9 largely accounts for the observed bias. The study extended to changing fluorine (F) for chlorine (Cl) and bromine (Br) at the pseudoanomeric position in the cyclohexanes. Although these halogens do not become involved in NCHBs, they polarize the geminal -CHX- hydrogen at the pseudoanomeric position to a greater extent than fluorine, and consequent electrostatic interactions influence conformer stabilities. [GRAPHICS] (AU) | |
| FAPESP's process: | 23/14064-2 - Modeling the Interaction of Janus-Face Cyclohexanes with dsDNA and ssDNA |
| Grantee: | Bruno de Almeida Piscelli |
| Support Opportunities: | Scholarships abroad - Research Internship - Doctorate (Direct) |
| FAPESP's process: | 18/03910-1 - Physicochemical studies of fluorinated organic compounds: experimental and theoretical approaches |
| Grantee: | Rodrigo Antonio Cormanich |
| Support Opportunities: | Research Grants - Young Investigators Grants |