E. A. Avetisyan

Stable fluoroaliphatic radicals containing functional groups: Synthesis and reactivity

Abstract β -Fluorosulphatoperfluoroalkyl radicals ( 3, 7 and 8 ) are obtained by the reaction of fluoroolefins (HFP trimer and dimer, and perfluoro4 4-dimethylpent-2-ene, respectively) with (FSO 3 ) 2 . The pure β -fluorosulphatotetrafluoroethylperfluorodiisopropylmethyl radical ( 3 ) has been isolated and converted to the perfluoroacetyldiisopropylmethyl radical ( 4 ) under the action of CsF. The reaction of radicals 3,7 and 8 with SbF 5 leads to the replacement of the FSO 3 group by a fluorine atom. The ability of the FSO 3 group in β -fluorosulphatoperfluoroalkyl radicals to play the role of a leaving group is explained by the stabilizing effect of the unshared electron on the adjacent carbocation centre.

Synthesis of the perfluoroacetyldiisopropylmethyl radical

A stable trifluoroacetylperfluorodiisopropylmethyl radical has been prepared by interaction of the (α-fluorosulfonyloxytetrafluoroethyl)perfluorodiisopropylmethyl radical with anhydrous CsF. This reaction is the first example of a chemical transformation of a C-centered radical which is not resonance-stabilized with retention of the radical center.

ESR study of the free radicals formed in the photolysis of α-ketofluorosulfates

ESR spectroscopy was used to establish that the UV irradiation of α-ketofluorosulfates containing an OSO2F group at a tertiary carbon atom gives radicals formed upon cleavage of the C-OSO2F bond. If the OSO2F group is attached to a primary or secondary carbon atom, we observe ordinary photodecomposition with cleavage of the acyl—carbon bond. The ESR spectra of the new radicals were studied. Replacement of fluorine by the OSO2F group in the trifluoromethyl radical leads to compression of the radical site. Branched α-oxoperfluoroalkyl radicals are not heteroallylic and the unpaired electron is localized largely on the carbon atom. The [(CF3)2CF]2ĊC(O)CF3 radical is stable in the air.

Structure and reactivity of perfluorinated branched α-ketoradicals

Abstract Fluoroaliphatic hydroxyketoradicals prepared by photochemical reduction of the corresponding α-diketones and (i-C3F7)2C⋅C(O)CF3 react with hydrogen abstraction (according to ESR data). The hydroxyketoradicals are shown to dimerize reversibly, and the dimerization rate decreases in the presence of polyfluorinated alcohols due to the formation of radical–alcohol complexes.

Synthesis and studies of nucleophilic reactions of vicinal bis (fluorosulfonyloxy)perfluoroisononanes

The addition of peroxydisulfuryl difluoride (FSO3)2 to isomeric perfluoroisononenes (perfluoropropylene trimers) was studied. Isomers containing the trisubstituted C=C bond from adducts which were converted to the corresponding ketofluorosulfates under the action of weak nucleophiles (DMF and AcONa/AcOH) and underwent haloform-type decomposition under the action of CsF to form perfluoroalenyl fluorosulfates and products of their subsequent conversions.

The ESR study of reactivity of perfluoroacetyldiisopropylmethyl radical

The kinetics of hydrogen abstraction from hydrocarbons by the air-stable perfluoroacetyldiisopropylmethyl radical was studied by ESR, and a reaction mechanism was proposed. The degree of delocalization of the unpaired electron in the model C(5)F3−C(1)·[C(2)(O(4))C(3)F3]C(6)F3 radical was calculated by the MNDO/PM3 method in the UHF approximation. For the conformation in which the CO group lies in the plane passing through the C(1), C(2), and C(5) atoms, the electron density on the O atom is 0.22.

ELECTROCHEMICAL ADDITION OF FLUOROSULFONIC ACID TO PERFLUORO-2-METHYL-3-ISOPROPYL-2-PENTENE

Electrolysis of fluorosulfonic acid in the presence of perfluoro-2-methyl-3-isopropyl-2-pentene yields the products of addition of HSO3F at the double bond — 2-hydro-3-fluorosulfatoperfluoro-2-methyl-3-isopropylpentane and 2-fluorosulfato-3-hydroperfluoro-2-methyl-3-isopropylpentane. The formation of monofluorosulfates probably includes the stage of one-electron reduction of the initial olefin.

Reaction of 2-trifluoromethylperfluoro-2-pentenyl fluorosulfate with nucleophilic reagents

Abstract2-Trifluoromethylperfluoro-2-pentenyl fluorosulfate undergoes SN2′ nucleophilic reactions. The reaction of this fluorosulfate with halide salts gives an equilibrium mixture of 1-halo-2-trifluoromethylperfluoro-2-pentene and 2-trifluoromethyl-3-haloperfluoro-1-pentene.

Reaction of perfluoropropenylbenzene with sulfur trioxide

Depending on the ratio of the reagents and the reaction conditions, the reaction of perfluoropropenylbenzene with SO3 in the presence of BF3 or SbF5 gives perfluoro-γ-phenylallyl fluorosulfate or perfluorocinnamoyl fluorosulfate; hydrolysis of the latter gives perfluorocinnamic acid.