The seeming lack of CF⋯HO intramolecular hydrogen bonds in linear aliphatic fluoroalcohols in solution

Abstract

No CF⋯HO intramolecular hydrogen bonds (IHBs) in 2-fluoroethanol, 3-fluoropropanol and 4-fluorobutanol can be detected experimentally in solution by NMR and infrared spectroscopies. According to ab initio (MP2/aug-cc-pVDZ) and DFT calculations (B3LYP), a CF⋯HO IHB has no influence on the conformational behavior of 2-fluoroethanol, while it stabilises the global minima of 3-fluoropropanol and 4-fluorobutanol for the isolated molecules. Entropy and bulk solvation effects, even in nonpolar media, such as CCl₄, cyclohexane and dichloromethane, are indicated to diminish the population of these global minima, apparently below the detection limit.