Homolytic reactions of polyfluoroaromatic compounds IX. Abstraction reactions of some p-substituted tetra-fluorophenyl radicals

The decomposition of pentafluoroaniline, 2,3,5,6-tetrafluoroaniline and its 4-bromo and 4-methoxy analogues by pentyl nitrite gives the corresponding aryl radicals which, when generated in the presence of chloroform, carbon tetrachloride, or bromotrichloromethane, remove atoms from these solvents to give substituted benzenes. The ease of removal of X from XCCl₃ decreases in the order X = Br,H > Cl.The yield of substituted benzene product depends upon the p-substituent of the polyfluoroaniline and is greatest for tetrafluoro-p-anisidine.     

Homolytic reactions of polyfluoroaromatic compounds. X. Biphenylyl radicals in the thermolysis of aroyl peroxides in polyfluoroaromatic solvents

The thermolyses of a number of aroyl peroxides in hexafluorobenzene, and of benzoyl peroxide in octafluorotoluene, gave the corresponding biaryls which were isolated by steam distillation. Mass spectrometry of the residues showed evidence of biphenylyl radicals arising from the arylation of the peroxides themselves or, possibly, of the derived aroic acids. Terphenyls, and the corresponding σ-intermediate radicals, could be found, and the relative molecular masses of the latter components showed that subsequent arylation of the main binuclear products was not the main source of terphenyls.     

Homolytic reactions of polyfluoroaromatic compounds. Part XII. Aryldehydrogenation and aryldefluorination in polyfluorobenzenes

The thermal decomposition of benzoyl peroxide in a range of polyfluorobenzenes at 80° gives biaryls arising from both the displacement of fluorine and hydrogen. Phenyldefluorination predominated only in the attack of 1,2,3,4-tetrafluorobenzene and of pentafluorobenzene, but was evident even in the attack of $\text{o}$-difluorobenzene. The relative rates of displacement, as shown by the isomer distributions, were generally well reflected by the application of partial rate factors found in the phenylation of fluorobenzene; however, phenyldefluorination was not so easily amenable to this treatment, a possible consequence of complex formation between radical precursor and substrate.     

Homolytic reactions of polyfluoroaromatic compounds Part VI. The mechanism of the phenylation of hexafluorobenzene

The decomposition of phenylazotriphenylmethane in hexafluorobenzene gives very little 2,3,4,5,6-pentafluorobiphenyl, since no mechanism exists for the defluorination of the radical intermediate. The yield of biaryl is raised by added benzoic acid, although this also introduces a competition with the substrate for the radicals and their precursor. The decomposition of benzoyl peroxide in hexafluorobenzene gives pentafluorobiphenyl, the yield of which increases considerably when the reaction is caried out in the presence of p-fluorobenzoic acid; in the latter case, 2,3,4,4′,5,6-hexafluorobiphenyl is also found.A mechanism incorporating these observations is suggested.     

Homolytic reactions of polyfluoroaromatic compounds Part VIII. The decomposition of benzoyl peroxide in hexafluorobenzene

The decomposition of benzoyl peroxide in hexafluorobenzene proceeds by a spontaneous first-order process accompanied by an induced decomposition showing 1.5-order dependence upon the concentration of the peroxide. The induced decomposition is associated with the formation of 2,2′,3,4,5,6-hexafluorobiphenyl and benzoic acid. 2,3,4,5,6-Pentafluorobiphenyl is the main product at all concentrations of peroxide; small amounts of other compounds are formed, together with a high-boiling residue probably containing isomeric dodecafluorotetrahydroquaterphenyls. The mechanism is discussed.     

Homolytic reactions of polyfluoroaromatic compound. Part XI. Confirmation of the proposed mechanism of phenylation of polyfluoroaromatic substrates

The derivatives of dihydrobiphenyl, which were predicted [1,2] to be formed in the thermolysis of benzoyl peroxide in polyfluoroaromatic compounds and which arose from transesterification, have been identified in the reactions of hexafluorobenzene and of octafluorotoluene with this peroxide. The presence of 1,4-dihydro-1,2,3,4,4,5,6-heptafluorobiphenyl (or its positional isomer, 1,2-dihydro-1,2,2,3,4,5,6-heptafluorobiphenyl) in such reaction mixtures also explains the formation of 3,4′-$\text{bis}$(phenyl)-octafluorobiphenyl in the dehalogenation products of the polynuclear residue from the reaction in hexafluorobenzene. Fluorine migration [3] does not need to be postulated.The yield of 2,3,4,5,6-pentafluorobiphenyl from the thermal decomposition of phenylazotriphenylmethane (PAT) in hexafluorobenzene at 80° is generally increased by the presence of a variety of hydrogen donors. Larger amounts of additive increase the yield of biaryl with respect to PAT, but not usually with respect to the additive.These results are consistent with the mechanism of arylation of polyfluoroaromatic compound previously suggested [1,2].     

Homolytic reactions of polyfluoroaromatic compounds Part VII. Products and relative rates of phenylation of pentafluorobenzene,bromopentafluorobenzene and octafluorotoluene with benzoyl peroxide

Competitive rates of arylation of the title compounds were measured using hexafluorobenzene as reference. The results suggest that the species responsible for intermolecular discrimination and those responsible for intramolecular selection are not the same. The significance of this observation is discussed.     

Interaction of polyfluoroaromatic compounds with o-aminophenol. The Smiles rearrangement in the polyfluoroaromatic series

The reactions of polyfluoroaromatic compounds containing an electron-attracting substituent other than fluorine in the aromatic ring with o-aminophenol proceed at the amino or hydroxy group and lead to the corresponding hydroxydiarylamines (in neutral media) or aminodiaryl ethers (in alkaline media). The latter compounds, unlike 2,3,4,5,6-pentafluoro- 2'-aminodiphenyl ether, are transformed in dimethylformamide (DMFA) to isomeric polyfluoro-2-hydroxydiarylamines (the Smiles rearrangement). The increased electron-attracting capacity of substituent leads to the decreased activation energy and increased rearrangement rate constants.     

The nucleophilic reaction of polyfluoroaromatic compounds: II. The nucleophilic cyclization of chloropentafluorobenzene

The results of cyclization reaction between chloropentafluorobenzene and bifunctional nucleophiles such as XCH₂CH₂OH(X=OH, NHMe, NHEt) and HN (CH₂CH₂OH)₂, NH₂CH₂CH₂NH₂ were reported. It was found that the NaH/DMF system was a better reagent for the preparation of sodium alcoholates and the yields of cyclic products ranged from 50–80% which were much higher than that reported by previous workers.³     

Homolytic aromatic substitution by heterocyclic free radicals. Reaction of 3-quinolyl and 8-quinolyl radicals with aromatic compounds

Free radicals obtained from 3- and 8-aminoquinolines were studied in various aromatic substrates. Isomer percent, reaction yields, and overall reactivities towards benzene are recorded.     

多氟芳烃的亲核反应II: 一氯五氟苯的亲核环化

本文报道一氯五氟苯与双官能团亲核试剂反应制备环化产物的研究结果, 发现应用NaH-DMF体系制备醇钠, 有利于亲核反应的顺利进行, 环化产物产率有较大幅度提高.     

Phosphorylation of polyfluoroaromatic compounds

Conclusions Polyfluoroaromatic compounds react with Na dimethyl and diethyl phosphites and diethyl thiophosphite in the Michaelis-Becker reaction with formation of the corresponding methyl and ethyl polyfluoroarylphosphonates and thiophosphonates.For Communication 2, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 867–869, April, 1981.     

Low-temperature reaction of magnesium with fluorobenzene

The low-temperature reaction of magnesium with fluorobenzene has been investigated. Joint condensation of magnesium and fluorobenzene vapours at low temperatures quantitatively gave phenylmagnesium fluoride in one stage.     

Hydrogen abstraction reactions from organosilicon compounds. The reactions of fluoromethyl radicals with trichlorosilane. The photolyses of di- and tetrafluoroacetone

The photolyses of 1,3-difluoro- and 1,1,3,3-tetrafluoroacetone have been reinvestigated as sources of fluoromethyl radicals, and the following rate constant ratios were determined

1 θ= 2.303 RT in kcal/mole.

The results are in substantial agreement with the original investigations. The photolyses of the fluoroacetones were used as sources of CH₂F and CHF₂ radicals, and the following Arrhenius parameters were obtained for the hydrogen abstraction reactions R + SiHCl₃ → RH + SiCl₃:

Homolytic reaction of trialkylvinylstannanes with alkanethiols

Conclusions Benzene and triethylbromostannane were identified in the reaction products when the reaction of triethylvinylstannane with n-butanethiol in bromobenzene as the medium was initiated with UV light. The formation of these compounds confirms the previously proposed mechanism of the homolytic thiylation of trialkylvinylstannanes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1664–1665, July, 1978.     

The reactivity of ketyl and alkyl radicals in reactions with carbonyl compounds

A parabolic model of bimolecular radical reactions was used for analysis of the hydrogen transfer reactions of ketyl radicals: >C·OH+R¹COR²→>C=O+R¹R²C·OH. The parameters describing the reactivity of the reagents were calculated from the experimental data. The parameters that characterize the reactions of ketyl and alkyl radicals as hydrogen donors with olefins and with carbonyl compounds were obtained: >C·OH+R¹CH=CH₂→>C=O+R¹C·HCH₃; >R¹CH=CH₂+R²C·HCH₂R³→R²C·HCH₃+R²CH=CHR³. These parameters were used to calculate the activation energies of these transformations. The kinetic parameters of reactions of hydrogen abstraction by free radicals and molecules (adelhydes, ketones, and quinones) from the C−H and O−H bonds were compared. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2178–2184, November, 1998.