Nuclear Magnetic Resonance Study of Hydrogen Bonding in 1,1,1-Trifluoro-2-hydroxy-4-alkanones

Addition of fluoral at the α-carbon of 3-pentanone, cyclohexanone, 4-methyl-2-pentanone, and acetone gives 1,1,1-trifluoro-2-hydroxy-3-methyl-4-hexanone (1a and b, diastereomers), 2-(1-hydroxy-2,2,2-trifluoroethyl)cyclohexanone (2a and b, diastereomers), 1,1,1-trifluoro-2-hydroxy-6-methyl-4-heptanone (3), and 1,1,1-trifluoro-2-hydroxy-4-pentanone (4), respectively. Hydrogen-bonding studies, based on proton and fluorine n.m.r. measurements, show strong intramolecular [Formula: see text] bonding with relatively weak intermolecular interactions in 1a and 2a, and intermolecular [Formula: see text] bonding in 1b, 2b, 3, and 4.