Fluorine increase stability

Theoretical studies have indicated that m-bcnzync is monocyclic with a C(l)-C(3) distance of 2.0 A whereas in tetrafluoro-w-benzyne the increased eclipsing strain between fluorine atoms stabilizes the bicyclo[3.1.0]hexatriene form with a C(l)-C(3) distance of 1.75 A.56 Computational studies coupled with gas-phase experimental studies show that appropriate substituents can be used to tune the reactivity of 1,3-arynes. Thus the presence of NH+ at C(5) makes (13) mildly carbocationic whereas the addition of OH at C(4) in (14) gives a highly reactive (bi)radical.57... 

Poly-a,P,P trifluorostyrene has slightly lower stability than polystyrene (Table 12). The relatively large amount of monomer formed suggests that chain scission is followed by depolymerization. Poly-2,3,4,5,6 penta-fluoropolystyrene is much more stable than polystyrene (Table 12). Wall et al. [269] attributed this increased stability to the loss of resonance interaction between the phenyl group and the chain because of the presence of the fluorine atoms. Perfluorostyrene polymerized by 7-irradiation has, however, been found recently to have a stability close to that of polystyrene a rate of weight loss of 0.4% per min was found at 335°C and complete decomposition of the polymer is observed at 432°C [270],... 

In the case of meta-trifluoromethyl benzoic acid, the great increase in the relative acidity is due not to any resonance stabilization, but to the strong inductive effects of the highly electronegative fluorines. This stabilizes the free negative charge of the ir-cloud. 

Presumably this reflects an increasing stabilization of the saturated product of the reaction, with greater fluorine content, due to ionic-covalent resonance. 

Oxidative metabolism of phenyl rings is a common problem, and fluorine substitution, usually at the 4-position, has become a wide-spread practice to increase stability in various substance classes. A plot of Hammett c coefficients against... 

We calculated the relative energies of the alkyne and vinylidene isomers at HF/II, HF/III, MP2/III, and MP3/III. The results are shown in Table 18. The additional f-type polarization function in basis set III has little effect on the relative energies of the isomers. Relative energies of the alkyne and vinylidene isomers are similar at the MP2 and MP3 level, so the predicted stability order should be quite reliable. The calculations predict that substitution of hydrogen by the more electronegative substituent fluorine increases the relative stability of the vinylidene isomer, which is in agreement with experimental evidence. In... 

Besides FEC and TFPC, more advanced stmctures of fluorinated cyclic carbonates have also been synthesized and evaluated in Li-ion batteries. Two examples of such molecules are given in Fig. 2. These molecules have traditionally been used in specialized applications such as coolants and supercapacitors, and their use in Li-ion batteries is relatively new [5, 6, 74, 78]. Regardless, these molecules have shown increased stability toward oxidation, better thermal stability, and low flammability. 

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