Reactions in anhydrous hydrogen fluoride

Symmetrical N-benzyl-substituted hexahydrotriazines(I), benzylamines, benzaldehydes, and diphenylmethanes are synthesized by reacting aromatic compounds with urotropine in anhydrous hydrogen fluoride. A mechanism for the reaction is suggested, and the hypothesis advanced that the primary products of Duff's reaction are type I compounds.For Part I see [1].     

Reactions in anhydrous hydrogen fluoride Communication 5. Fluoroaminomethylation and fluoroacylaminomethylation of haloolefins

Conclusions The new reaction of conjugated fluoroaminomethylation of chloro and fluoro olefins is described; it may be used for the synthesis of various fluorine-containing amines.For Communications 3 and 4 see Zh. Vses. khim. obshch. im. D. I. Mendeleeva11, 354, 356 (1966).This article is published in accordance with a resolution of the conference of editors-in-chief of journals of the Academy of Sciences of the USSR of July 12, 1962, as a dissertation paper by A. V. Podol'skii.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 1575–1581, September, 1966.We thank É. I. Fedin and P. V. Petrovskii for determining and interpreting the spectra.     

Reactions of periodate in anhydrous hydrogen fluoride and the partial hydrolysis of iodine heptafluoride

Solutions of sodium periodate or periodic acid in anhydrous hydrogen fluoride contain HOIOF₄ as well as other unidentified fluorine containing species. Partial hydrolysis of iodine heptafluoride yields first IOF₅ and with increased water addition, HOIOF₄, which is dissociated to produce the IO₂F₄⁻ ion. Raman, i.r. and ¹⁹F NMR spectra of this anion have been obtained, and C_2v symmetry has been assigned.     

Arsenic pentafluoride equilibria in anhydrous hydrogen fluoride

Earlier work has indicated that arsenic pentafluoride when dissolved in anhydrous HF is present largely as the anion As₂F₁₁^-, particularly temperatures much below ambient. Raman spectra and conductance measurements are used here to show that, at and near room temperature, there are significant concentrations of molecular AsF₅, AsF₆^- and As₂F₁₁^-in equilibrium and that on reduction of temperature, As₂F₁₁^- is formed at the expense of AsF₅ and AsF₆^-. The implications of the Lewis acid and oxidant strengths of AsF₅ are discussed as affecting synthetic procedures in anhydrous HF.     

The autoprotolysis constant of liquid anhydrous hydrogen fluoride

The autoprotolysis constant of HF K: [H⁺][F^?] = 10^?12.50 ( I : 0.1, KSbF₆, 0° C ) has been evaluated from potentiometric titrations of solutions of H⁺ with F^?. The F^? concentrations were determined with the help of an Ag electrode acting in the presence of HCl and AgCl as a F^? electrode.     

Regio - and stereospecific halogenation of 7alogenoalkenes in liquid hydrogen fluoride

The products of bromo and chlorofluorination of E and Z-1,2-dichloroethylenes, 1, 3-dichloro-1-propenes, 1, 1-dichloro- ethylene and 1, 3-dichloro-2-fluoro-1-propene by N-bromosuccinimide and hexachloromelamine in anhydrous hydrogen fluoride have been studied. It was found that the reaction was in all cases 100% regio and 93–100% trans-stereospecific with the exception of E-1, 2-dichloro-ethylene, its trans-stereospecificity being 85%.Threo and erithro-1-bromo-1, 2-dichloro-2-fluoroethanes, 2-bromo-1, 3-dichloro-1-fluoropropanes and 1, 2, 3-trichloro-1-fluoro-propanes as well 1, 1, 2-trichloro-2-fluoroethane, 1-bromo-2, 2-dichloro-2-fluoroethane, 1, 2, 2-trichloro-2 fluoroethane, 1-bromo-1, 3-dichloro-2, 2-difluoropropane, and 1, 1, 3-trichloro-2,2-difluoropropane were obtained in 50–70% yield.The bromination of E and Z-1, 3-dichloro-1-propenes with molecular bromine in carbon tetrachloride in the dark is non-stereospecific and gives a mixture of erithro and threo-1, 2-dibromo-1, 3-dichloropropanes in the ratio about 1:1. However, the bromination reaction in anhydrous hydrogen fluoride solution proceeds with a high degree of stereospecificity (94–95%) and gives threo-1, 2-dibromo-1, 3-dichloropropane from Z and erithro-1, 2-dibromo-1, 3-dichloropropane from E-1, 3-dichloro-1-propene.The data obtained are considered in terms of an electrophilic mechanism of halogenoalkene halogenation in anhydrous hydrogen fluoride and a free-radical mechanism in carbon tetrachloride.     

Chemistry in hydrogen fluoride V. Catalysts for reaction of HF with halogenated olefins

Tantalum pentafluoride, niobium pentafluoride, titanium tetrachloride, and molybdenum pentachloride catalyze the addition of hydrogen fluoride to $\text{tetra}$- and $\text{tri}$chloroethene and related compounds. Hydrogenation of tetrachloroethene to 1,1,2,2-tetrachloroethane was observed using hydrogen, methylcyclopentane, and TaF₅ in HF.     

Solution properties of some pentafluorides and oxide tetrafluorides in anhydrous hydrogen fluoride

Solutions of transition metal pentafluorides, MF₅, M = Nb, Ta, Mo, Re and Os, and oxide tetrafluorides, MOF₄, M = Mo, W and Re, in anhydrous hydrogen fluoride have been prepared. The conductivity and Raman spectrum of the solutions have been recorded. The conductimetric measurements indicate that all the compounds are relatively weak fluoride ion acceptors; the order of Lewis acid strength is OsF₅ > ReF₅ > TaF₅ > MoF₅ > NbF₅ ⪢ ReOF₄ > WOF₄ > MoOF₄. None of the solutions contained sufficient amounts of MF₆⁻ or MOF₅⁻ ions to detect by Raman spectroscopy. The data obtained in this study are discussed, together with similar existing data on other pentafluoride-hydrogen fluoride solutions.     

Current methods for asymmetric halogenation of olefins

This Minireview discusses the progress made in developing reactions where an olefin is subjected to an asymmetric halogenation. It aims to serve as a reference for the studies reported to date, including preliminary work and mechanistic studies. The current state of the art, scope, and limitations of these processes are discussed.