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.