Hexafluorobenzene oxide

The behaviour of the corresponding hexafluoro derivative of (40b) in solution is somewhat different solutions of hexafluorobenzene oxide in nonpolar solvents are stable at room temperature. In acetonitrile or acetone, the hexafluorobenzene oxide rearranges spontaneously to hexafluorocyclohexa-2,4-dienone and not to hexafluorooxepin. However, NMR measurements in chlorobenzene at various low temperatures indicate the existence of a dynamic equilibrium between perfluorobenzene oxide and perfluoro-oxepin [289]. 

The hexafluorobenzene oxide 386 having no hydrogen atoms rearranges spontaneously to hexafluorocyclohexa-2,4-dienone 387 in polar solvents (acetonitrile, acetone) at room temperature as well as in non-polar solvents at elevated temperatures. Benzene oxide 386 is reduced under very mild conditions (sodium iodide in acetone at RT) to pentafluorophenol 388 (equation 183). 

Hexafluorobenzene oxide (39) exists in rapid equilibrium with its valence isomer hexafluorooxepin (40) at RT, but the equilibrium hes far on the side of... 

FIGURE 10.1 Equilibrium between F-oxepine and hexafluorobenzene oxide. 

Oxidative reactions of dienes are accomphshed under similar conditions as those of alkenes. Abicydic diene synthesized from hexafluorobenzene and 1,2-di-chloroethylene is monoepoxidized by triflnoroperoxyacetic acid [43] (equation 35). 

UV irradiation of a mixture of hexafluorobenzene in the presence of oxygen gives Dewar benzene oxide also as a minor product, which undergoes thermal transformation to hexafluorocyclohexa-2,4-dienone [J46] (equation 36)... 

Hexafluorinated Dewar benzene oxide 1 is prepared in 7% yield by the irradiation of hexafluorobenzene in the presence of oxygen,12 research undertaken in the hope of gaining access to the valence isomers perfluorobenzene oxide (3) and perfluorooxepin (4). Even gentle heating of 1 (50 C, 7d), however, leads only to perfluorocyclohexa-2,4-dien-l-one (2). Note that cyclohexadienone 2 is also the only product obtained from the pyrolysis of per-fluorobicyclo[2.2.0]hex-5-en-2-otie hydrate (see Section 5..3.2.1.). 

Hexafluorobenzene, perfluoromethylbcnzene, and octafluoronaphthalene are oxidized to the corresponding cation salts by dioxygenyl hexafluoroarsenate [45] (equation 38) Salts of monocyclic perfluoroaromatics are unstable above 15 °C, whereas that of octafluoronaphthalene is indefinitely stable at room temperatures... 

Oxidation of hexafluorobenzene to pentafluorophenol is accomplished by heating with concentrated hydrogen peroxide [46 (equation 39) Under these conditions, pentafluorobiphenyl is monohydroxylated on the nonfluonnated nng [46] (equation 40)... 

In view of the relative C—X bond energies, C—F bond activation can be expected to be strongly disfavored. Nevertheless, there is an increasing number of cases where C—F bond addition to electron-rich metal complexes is observed. For example, QF6 oxidatively adds to the Cp Rh(PMe3) fragment, whereas QF5H undergoes only C—H activation.65 Hexafluorobenzene slowly adds to... 

Sequential functionalization of pyrazole-l-oxides via regioselective metallation led to the synthesis of 3,4,5-trisub-stituted-l-hydroxypyrazoles <2002JOC3904>. 3-Acylated-2-(4-methoxybenzyl)-2//-pyrazole 1-oxides were formed by the reaction between a 3-magnesium 2//-pyrazole-l-oxide and acid chlorides <2002J(P1)428>. 3-Arylated-l-hydroxypyrazoles were synthesized from 3-metallated-pyrazole 1-oxides <2001JOC8654>. The reaction between hexafluorobenzene and the anion of 1-hydroxypyrazole affords a mixture of the products of bis-, tetrakis-, and hexakis-substitution <2004ARK100>. In the case of hexakis(bromomethyl)benzene, its reaction with 1-hydroxy-pyrazole leads to the hexakis-substituted product. 

The phenylcyclopropylcarbene generated upon irradiation of phenylcyclopropyl-diazomethane (166) in benzene, hexafluorobenzene or saturated and unsaturated hydrocarbons leads to 1-phenylcyclobutene (167) in nearly quantitative yield on the other hand, the cyclopropylcarbene formed on irradiation of 2,3-biscyclopropylstilbene oxide (168) leads to secondary photo-products of higher molecular weights (equation 115). ... 

Because of the extraordinary strength of the carbon-fluorine bond, transition metal-mediated activation of fluoroalkanes and arenes is not easy to achieve. Nevertheless, activation of the C-F bond in highly electron-deficient compounds such as 2,4,6-trifluoropyrimidine, pentafluoropyridine, or hexafluorobenzene is possible with stoichiometric amounts of bis(triethylphosphano) nickel(O) [101] (Scheme 2.45). More recently Herrmann and coworkers [102] have described a variant of the Kumada-Corriu cross-coupling reaction [103] between fluorobenzene and aryl Grignard compounds which uses catalytic amounts of nickel carbene complexes. Hammett analysis of the relative kinetic rate constants indicated that the reaction proceeds via initial oxidative addition of the fluoroaromatic reactant to the nickel(O) species. 

CADMIO (Spanish) or CADMIUM (7440-43-9) Cd Air exposure, especially of powdered form, may cause chemical to self-ignite. Finely divided material reacts violently with strong oxidizers, fused ammonium nitrate, bromine pentafluoride, lithium, nitryl fluoride, phosphorus trichloride, potassium chlorate carbon dioxide + heat, hydrozoic acid (possible explosion), nitric oxide, tellurium. Contact with acid forms explosive hydrogen gas. Contact with hexafluorobenzene forms a heat-sensitive explosive compound. May react with selenium, elemental sulfur, zinc. On small fires, use dry chemical powder (such as Puiple-K-Powder), foam, Halon, or CO2 extinguishers. 

ESTANO (Spanish) (7440-31-5) Finely divided material is combustible and forms explosive mixture with air. Contact with moisture in air forms tin dioxide. Violent reaction with strong acids, strong oxidizers, ammonium perchlorate, ammonium nitrate, bis-o-azido benzoyl peroxide, bromates, bromine, bromine pentafluoride, bromine trifluoride, bromine azide, cadmium, carbon tetrachloride, chlorine, chlorine monofluoride, chlorine nitrate, chlorine pentafluoride, chlorites, copper(II) nitrate, fluorine, hydriodic acid, dimethylarsinic acid, ni-trosyl fluoride, oxygen difluoride, perchlorates, perchloroethylene, potassium dioxide, phosphorus pentoxide, sulfur, sulfur dichloride. Reacts with alkalis, forming flammable hydrogen gas. Incompatible with arsenic compounds, azochloramide, benzene diazonium-4-sulfonate, benzyl chloride, chloric acid, cobalt chloride, copper oxide, 3,3 -dichloro-4,4 -diamin-odiphenylmethane, hexafluorobenzene, hydrazinium nitrate, glicidol, iodine heptafluoride, iodine monochloride, iodine pentafluoride, lead monoxide, mercuric oxide, nitryl fluoride, peroxyformic acid, phosphorus, phosphorus trichloride, tellurium, turpentine, sodium acetylide, sodium peroxide, titanium dioxide. Contact with acetaldehyde may cause polymerization. May form explosive compounds with hexachloroethane, pentachloroethane, picric acid, potassium iodate, potassium peroxide, 2,4,6-trinitrobenzene-1,3,5-triol. 

R.adical-CATION salts derived from hexafluorobenzene (I), octafluoro-toluene (2), pentafluoropyridine (3), and octafluoronaphthalene (4) have been known for some time, and some of their reaction chemistry has been discussed in a recent publication (5). Hexafluorobenzenehexafluoroarsenate, C6F6+AsF6", has oxidizing power sufficient to electron oxidize most other mono- and polycyclic aromatic compounds. 

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