Fluorine substituted ions

For p-, m- and a-fluorine-substituted ions of Iwnzyl type, 4-fluorine-substituted benzenium, 1,2,3,5,6-pentamethylbenzenium and 1-naphthalenium ions a similar dependence has been established... 

The spin-spin coupling constants of fluorine-substituted ions are presented... 

The INDO method has been used to analyse various contributions for fluorine-substituted ions to the values Ji3(, i9p. 

Silene 2, 1-fluorosilene 602 and 1,1-difluorosilene 603 have been examined by FT ion cyclotron resonance spectroscopy in order to estimate the jr-bond strength. Bracketing studies with various bases (B) and fluoride acceptors (A) gave values for the proton and fluoride affinity of the silenes284. The TT-bond energy was calculated by thermochemical cycles and found to increase with fluorine substitution. The data are given in Table 16. 

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 19F-NMR of bovine plasma amine oxidase [102] and A. coli amine oxidase [103] derivatized with fluorine-substituted hydrazines allowed estimation of the distance between the hydrazine and the active site Cu ion. The rather large distance that has been calculated precludes that the Cu ions are in the immediate... 

Formation of Ti02-xFx Compounds in Fluorine-Implanted Ti02. Fluorine substituted for oxygen sites in the oxide by ion implantation. 307... 

The effect of substituting fluorine for hydrogen in the methylene halides is to increase the rate of carbanion formation and presumably to stabilize the carbanion and decrease the pK. The effect of fluorine substitution on the acidity of other carbon acids is not so clear. In some cases fluorine substitution leads to a smaller increase in rate than expected from the inductive effect and in other cases results in a decrease in the rate of carbanion formation and an increase in pK values. The results shown in Table 6 were obtained for the rate coefficient (k) for methoxide ion catalysed carbanion formation per hydrogen atom by following the appearance of the MeOH absorbance in the IR spectrum when the esters were allowed to exchange in MeOD [167]. The acidity of the nitro-paraffins in Table 7 is mostly increased by chlorine substitution (p/T... 

Corina and coworkers65 gave the El mass spectra of two fluorinated ethyl methane-thiosulfonates (95 and 96), which showed distinct molecular ions and preferential S—S bond cleavage, in analogy with unsubstituted 93a. However, the extent of fluorine substitution affected the site of charge retention, so that base peaks at m/z 78, [CH2FCHS]+, and m/z 79, [MeS02]+, were found for 95 and 96, respectively. 

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