The geometries and interaction energies of complexes of pyridine with C6F5X, C6H5X (X=I, Br, Cl, F and H) and RFI (RF=CF3, C2F5 and C3F7) have been studied by ab initio molecular orbital calculations. The CCSD(T) interaction energies (Eint) for the C6F5X–pyridine (X=I, Br, Cl, F and H) complexes at the basis set limit were estimated to be −5.59, −4.06, −2.78, −0.19 and −4.37 kcal mol−1, respectively, whereas the Eint values for the C6H5X–pyridine (X=I, Br, Cl and H) complexes were estimated to be −3.27, −2.17, −1.23 and −1.78 kcal mol−1, respectively. Electrostatic interactions are the cause of the halogen dependence of the interaction energies and the enhancement of the attraction by the fluorine atoms in C6F5X. The values of Eint estimated for the RFI–pyridine (RF=CF3, C2F5 and C3F7) complexes (−5.14, −5.38 and −5.44 kcal mol−1, respectively) are close to that for the C6F5I–pyridine complex. Electrostatic interactions are the major source of the attraction in the strong halogen bond although induction and dispersion interactions also contribute to the attraction. Short‐range (charge‐transfer) interactions do not contribute significantly to the attraction. The magnitude of the directionality of the halogen bond correlates with the magnitude of the attraction. Electrostatic interactions are mainly responsible for the directionality of the halogen bond. The directionality of halogen bonds involving iodine and bromine is high, whereas that of chlorine is low and that of fluorine is negligible. The directionality of the halogen bonds in the C6F5I– and C2F5I–pyridine complexes is higher than that in the hydrogen bonds in the water dimer and water–formaldehyde complex. The calculations suggest that the CI and CBr halogen bonds play an important role in controlling the structures of molecular assemblies, that the CCl bonds play a less important role and that CF bonds have a negligible impact.

The (19)F NMR shieldings for 53 kinds of perfluoro compounds were calculated by the B3LYP-GIAO method using the 6-31G(d), 6-31+G(d), 6-31G(d,p), 6-31++G(d,p), 6-311G(d,p), 6-311++G(d,p), 6-311G(2d,2p), 6-311++G(2d,2p), 6-311++G(2df,2p), 6-311++G(3d,2p), and 6-311++G(3df,2p) basis sets. The diffuse functions markedly reduce the difference between the calculated and experimental chemical shifts. The calculations using the 6-31++G(d,p) basis set give the chemical shifts within 10 ppm deviations from experimental values except for the fluorine nuclei attached to an oxygen atom, a four- and a six-coordinated sulfur atom, and FC(CF(3))(2) attached to a sulfur atom.

A persistent perfluoroalkyl radical (PPFR), perfluoro-3-ethyl-2,4-dimethyl-3-pentyl, is shown to be a good source of •CF(3) radicals and a useful radical capable of initiating the polymerization of vinylidene fluoride (VDF). NMR characterizations of the resulting PVDF homopolymers showed that polymerization of VDF was exclusively initiated by •CF(3) radicals. The addition of •CF(3) radical onto VDF was regioselective leading to CF(3) -CH(2) -CF(2) -PVDF and the CF(3) end-group acted as an efficient label to assess the molecular weights by (19) F NMR spectroscopy. Various [PPFR](0) /[VDF](0) initial molar ratios lead to CF(3) -PVDF-CF(3) of different molecular weights. When that ratio decreased, both the molecular weights and the thermostability of these PVDFs increased, showing less defects of chaining and higher crystallinity.

Aus der Fluorierung von (I) geht das gegenüber Dimerisierung, O2, C12, Brz, I2 beständige, perfluorierte Alkylradikal (II) hervor, das jedoch mit F2 bei Zimmertemp.

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Batch radical homopolymerization of vinylidene fluoride (VDF) and its copolymerizations with seven fluorinated comonomers such as H 2 CCR A CF 3 (where R A stands for H, F, CO 2 R (R = H or tBu) or F 2 CCFR B (R B : H, CF 3 , OCF 3 ) initiated by • CF 3 radical generated from a perfluoro-3-ethyl-2,4-dimethyl-3-pentyl persistent radical (PPFR) are presented. That highly perfluorinated branched radical itself was unable to directly initiate the copolymerization in contrast to the generated trifluoromethyl radical that was successful. The microstructures of the resulting PVDFs, poly(VDF-co-H 2 CCR A CF 3 ) or poly(VDF-co-F 2 CCFR B ) (co)polymers were assessed by 19 F and 1 H NMR spectroscopy. 19 F NMR spectra displayed a quintet centered at −61 ppm assigned to a CF 3 end-group which enabled one to determine both the molecular weights of the resulting (co)polymers and the amounts (numbers and molar percentages) of these above comonomers. In all cases, the regioselective radical addition of • CF 3 onto the methylene site of VDF was noted as well as for 3,3,3trifluoropropene. In addition, the 19 F NMR spectra showed the absence of signals attributed to PPFR or its derivatives. According to [PPFR] o /([VDF] o + [comonomers] o ) initial molar ratios, this novel initiating system could produce high molecular weight-fluoropolymers (up to 200 000 g•mol −1 ). The lower that ratio, the higher their molecular weights as well as the higher their thermal stability (a 10% weight loss under air was noted at 425 °C). Although the kinetics of radical copolymerization were not studied, the presence of branched persistent radical did not disturb the reactivities of the comonomers and it was not involved in the primary recombination of radicals in the termination step of the polymerization while the macromolecular recombination was favored. For an initial PPFR concentration lower than 1 mol %, a feed ratio of ca. 20 mol % of 2-trifluoromethacrylic acid, MAF (or tert-butyl 2-trifluoromethacrylate, MAF−TBE) led to alternated poly(VDF-alt-MAF or MAF−TBE) copolymers. High yields (90%) of copolymers based on VDF and 2,3,3,3-tetrafluoroprop-1-ene, hexafluoropropylene (HFP), or perfluoromethyl vinyl ether (PMVE) comonomers were achieved while those from MAF, MAF−TBE, trifluoroethylene, and 3,3,3-trifluoropropene were fair to satisfactory. As expected, for a reasonable amount of HFP and PMVE inserted in the copolymers (>18 mol %), elastomers endowed with low T g values (−35 and −42 °C, respectively) were produced. In addition, the higher the content of VDF, the lower the T g , though the presence of tBu from MAF−TBE slightly increased the T g values. Copolymers containing MAF or MAF−TBE exhibited poor thermostability (that arises from the decarboxylation and isobutylene elimination from MAF or MAF−TBE, respectively) in contrast to the other VDF-containing copolymers that showed decomposition from 250 °C under air.

This work has demonstrated that a previously unexplored approach to separation of enantiomers via formation of diastereomeric derivatives with three stereogenic centers has obvious practical potential and deserves further systematic study. The design reported here is based on the unusual application of a configurationally unstable stereogenic nitrogen, which plays a key role in setting up the stereochemical match between the three stereogenic centers in the corresponding products.