...for the flexible 1-chloro-1,1-difluoro-2-pentanol unveiled using multinuclear magnetic resonance.
a Department of Chemistry, Federal University of Lavras, 37200-000, Lavras, MG, Brazil
b Institute of Chemistry, University of Campinas, 13083-970, Campinas, SP, Brazil
Received 1 December 2017, Revised 4 January 2018, Accepted 5 January 2018, Available online 8 January 2018.
Abstract
The preferred conformations of a small polyfunctional molecule containing fluorine, chlorine and hydroxyl groups, the 1-chloro-1,1-difluoro-2-pentanol (CDP), were completely elucidated using 1H, 13C and 19F NMR in three different solvents. While the Cl-C-C-O dihedral angle was asserted using coupling constant data for the diastereotopic fluorines, the Et-C-C-O torsional angle was analyzed by means of 1H NMR spectra with selective irradiation of the diastereotopic hydrogens and fluorines. In addition, unusual couplings of the hydroxyl hydrogen with a diastereotopic hydrogen and fluorines provided information on the O-H orientation. The behavior of 1JC,F when the solvents varied agrees with a weak F⋅⋅⋅HO intramolecular hydrogen bond. These findings were corroborated, and the governing interactions rationalized with the aid of high level CCSD(T) theoretical calculations. Noteworthy, hyperconjugation involving the electron-acceptor σ*C-Cl orbital drives the conformational equilibrium rather than the fluorine gauche effect.
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