2-Fluoro-2-propyl cation

Halogen as Heteroatom. In 1966 Olah, Cupas, and Comisarow511 reported the first a-fluoromethyl cation. Since then, a large variety of fluorine-substituted carbocations have been prepared. a-Fluorine has a particular ability to stabilize carbocations via back-donation of its unshared electron pairs into the vacant p orbital of the carbocationic carbon atom. 19F NMR spectroscopy is a particularly efficient tool for the structural investigations of these ions.512,513 The 2-fluoro-2-propyl cation 247 (NMR spectra, Figure 3.16) and 1-phenylfluoroethyl cation 248 are representative examples of the many reported similar ions.514... 

The A-esterases now classified as diisopropyl fluorophosphatases (diiso-propyl-fluorophosphate fluorohydrolase, DFPase, somanase, EC 3.1.8.2) were previously listed under EC 3.8.2.1. These enzymes, which hydrolyze P-F and P-CN bonds such as those of nerve gases, should be described as organophosphorus acid anhydrolases rather than phosphatases [56]. Diisopropyl-fluoro-phosphatases exist in different forms with contrasting substrate specificities. One form is able to hydrolyze paraoxon at a low rate, while others have no paraoxonase activity. The different forms differ in their molecular weights and in their requirements for bivalent cations for activity [56]. 

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