Sulfur tetrafluoride physical properties

Physical Properties. Sulfur tetrafluoride has the stmcture of a distorted trigonal bipyramid, the sulfur having hybrid sp d orbitals and an unshared electron pair (93). The FSF bond angles have been found to be 101° and 187°, and the bond distances 0.1646 and 0.1545 nm (94). 

Basic physical properties of sulfur tetrafluoride are given in Table l.2-3... 

Sulfur tetrafluoride was among the first reagents to be used for the direct substitution of hydroxy groups by fluorine. Good yields are only achieved with relatively acidic alcohols, such as nitro alcohols, polyhalo alcohols and hydroxy carbonyl compounds. The fluorination of simple aliphatic alcohols with sulfur tetrafluoride results in side reactions, such as formation of ethers, hence fluorination using other methods (vide infra) is preferred. Moreover, sulfur tetrafluoride cannot be handled without special pressure apparatus and requires precautions to be taken due to its physical and toxicological properties, hence it is, nowadays, frequently replaced by other reagents, but it is still in use for relatively inert substrates (see Vol.ElOa, p 321 ff, also Houben-Weyl. Vol. 5/3. pp 84-86). 

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