C-F bond fluorine

The fact that only 12 compounds containing C-F bonds have been found in nature so far [87] leads to the questions of (a) whether this is a consequence of the difficulty of forming C-F bonds in the first place, and (b) whether subsequent enzymic transformations in plants and animals are inhibited by the presence of C-F bonds. Fluorine, as fluoride ion, although extremely abundant, is present in largely insoluble salts. Moreover, fluoride ion is extensively hydrated because of the strength of hydrogen bonding, and in... 

One of the most common monovalent isosteric replacements is the substitution of hydrogen with fluorine [7]. These atoms have similar van der Waals radii but different electronic effects, fluorine being the most electronegative element in the periodic table. Due to the high strength of the C—F bond, fluorine is often introduced to achieve metabolic stability. Moreover, due to its high electronegativity, fluorine can be introduced to reduce basicity of proximal amines or increase acidity of proximal adds and also to introduce a conformational bias in molecules. 

The solubilities of fluorinated surfactants are related to the unusual properties of the fluorine atom and the C—F bond. Fluorine is the most electronegative element and is very difficult to polarize. Fluorine can form a very stable bond with hydrogen or carbon (see Section 3.1). The rigidity of the C— F bond causes stiffening of the perfluoroalkane chain and limits interactions with other molecules. Because of their small size, fluorine atoms can shield the perfluorinated carbon atom without steric stresses. Perfluoromethyl or perfluoromethylene groups therefore form compounds with very weak intermolecular forces. As a consequence of weak interactions, perfluoroalkanes are insoluble in common organic solvents. Perfluo-roalkanes are more hydrophobic than hydrocarbons, evidenced by solubility data CF4 is seven times less soluble in water than CH4 [1,2]. Water is almost 7 times less soluble in perfluoroheptane than in heptane on a equal weight basis [3] and 25 times more on a molar basis. 

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