With lead dioxide

Manganese(II) can be titrated directly to Mn(III) using hexacyanoferrate(III) as the oxidant. Alternatively, Mn(III), prepared by oxidation of the Mn(II)-EDTA complex with lead dioxide, can be determined by titration with standard iron(II) sulfate. 

Oxidative Fluorination of Aromatic Hydrocarbons. The economically attractive oxidative fluorination of side chains in aromatic hydrocarbons with lead dioxide or nickel dioxide in Hquid HF stops at the ben2al fluoride stage (67% yield) (124). 

Diphenylmethane Base Method. In this method, the central carbon atom is derived from formaldehyde, which condenses with two moles of an arylamine to give a substituted diphenylmethane derivative. The methane base is oxidized with lead dioxide or manganese dioxide to the benzhydrol derivative. The reactive hydrols condense fairly easily with arylamines, sulfonated arylamines, and sulfonated naphthalenes. The resulting leuco base is oxidized in the presence of acid (Fig. 4). 

Solutions of colourless pyrazolidinediones give highly coloured solutions of radicals (113) when treated with lead dioxide. The ESR spectra of these radicals have been recorded (78JOC808). They dimerize to tetrazenes (114) which appear to be indefinitely stable. 

Various 2,6-di8ubstituted p-benzoquinones have been prepared by oxidation of the corresponding 2,6-disubstituted phenols with potassium nitrosodisulfonate or lead dioxide in formic acid. Oxidative coupling of 2,6-disubstituted phenols to poly-2,6-disubstituted phenylene ethers followed by treatment of the polymers in acetic acid with lead dioxide is reported to give low yields of the corresponding 2,6-disubstituted p-benzoquinones. 

Hydroxyisophthalic acid has been prepared by oxidizing 2-hydroxy-3-methylbenzoic acid with lead dioxide, by cleaving the ether group of 2-methoxyisophthalic acid with hydriodic acid, and by hydrolyzing 2-iodoisophthalic acid with alcoholic sodium hydroxide. ... 

Great differences m product structures and distnbuaons are obtained dunng oxidation with lead dioxide or tetraacetate in different solvents and media [63, 64,65J Oxidation of pentafluorophenol with lead tetraacetate gives perfluoro-2,5-cyclohexadien-l-one in good yield [6 ] (equation 57)... 

PhSSPh and N2 via the intermediate formation of the purple radical [(PhSlaN], which is readily detected by its five-line (1 2 3 2 1) EPR spectrum. This radical is also generated by the oxidation of (PhSfaNH with lead dioxide. ... 

Phenotellurazine bis(trifluoroacetates) can be obtained by the oxidation of A-methylphenotellurazines with lead dioxide in trifluoroacetic acid solution. The... 

Barium sulfide explodes weakly on heating with lead dioxide or potassium chlorate, and strongly with potassium nitrate. Calcium and strontium sulfides are similar. 

Incandescence on warming with lead dioxide or potassium permanganate. 

Warm potassium reacts explosively with lead dioxide, and sodium probably behaves similarly [1], Magnesium reacts violently [2], and powdered aluminium probably does also, as it reacts violently with the monoxide [3], Mixtures of powdered molybdenum or tungsten with the dioxide incandesce on heating [4], The combination with zirconium is rated highest on a scale for sensitivity to deflagration, friction, ignition and static electrical initiation [5],... 

Calcium sulfide, strontium sulfide or barium sulfide react vigorously with lead dioxide on heating. 

Hydroxylamine ignites in contact with lead dioxide [1], while phenylhydrazine immediately reacts vigorously [2],... 

Boron or yellow phosphorus explode violently on grinding with lead dioxide, while red phosphorus ignites [1]. Mixtures with sulfur ignite on grinding or addition of sulfuric acid [2], An initiating mixture of silicon and lead dioxide (2 1) attains a temperature around 1100°C after ignition by a small flame [3],... 

The synthesis of polysulfide elastomers involves the use of a small amount of trichloroalkane in addition to dichloroalkane and sodium sulfide in order to form a branched polymer. The prepolymer is treated with a mixture of sodium hydrosulfide and sodium sulfite followed by acidification to convert all end-groups to thiol groups. Further polymerization and crosslinking is achieved by oxidative coupling of the thiol end-groups by treatment with lead dioxide, p-quinone dioxime, or other oxidizing agent... 

Plates of lead, each coated with lead dioxide, are immersed in fairly concentrated sulphuric acid. Lead is oxidized at the lead anode during discharge ... 

The nitrosodisulfonate salts, particularly the dipotassium salt called Fremy s salt, are useful reagents for the selective oxidation of phenols and aromatic amines to quinones (the Teuber reaction). - Dipotassium nitrosodisulfonate has been prepared by the oxidation of a hydroxylaminedisulfonate salt with potassium permanganate, " with lead dioxide, or by electrolysis. This salt is also available commercially. The present procedure illustrates the electrolytic oxidation to form an alkaline aqueous solution of the relatively soluble disodium nitrosodisulfonate. This procedure avoids a preliminary filtration which is required to remove manganese dioxide formed when potassium permanganate is used as the oxidant. " ... 

Phenyl-l,2,4-triazoline-3,5-dione has been prepared by oxidizing 4-phenylurazole with lead dioxide,7 and with ammoni-acal silver nitrate followed by an ethereal solution of iodine.8 The yields are low for both methods. 4-Substituted triazoline-diones can also be made by oxidation of the corresponding urazole with fuming nitric acid9 or dinitrogen tetroxide.10 Oxidation by <-butyl hypochlorite in acetone solution has also been described 1112 it, however, yields an unstable product, even after sublimation. Either dioxane12 or ethyl acetate are preferred as solvents for the reaction, since the product is obtained in a stable form. The latter solvent is superior since... 

When heated with lead dioxide, at 250°C, the same product, lead tetroxide is obtained ... 

Condensation of 2-mol equivalents of 9-aminocarbazole with ethyl orthoformate-boron trifluoride yielded the formamidine 127, which was oxidized with lead dioxide to the spectrally observable radical 128 in solution. ... 

CH2)2L0) were prepared. - " Such compounds can be oxidized with lead dioxide to N-picryl-9-aminocarbazyls (133). These black species are dehydrogenating agents though stable in dry chloroform the transformation of violet-black color into orange in benzene solution suggests that they... 

The curing of liquid thiokol is based on the reaction of the liquid polymer with lead dioxide or peroxides. Dehydrogenation of the terminal groups of the mercaptan chains of the polymer then takes place followed by elongation of the chains. This reaction may be depicted as ... 

Trimethylcyclopentanone has been prepared by the oxidation of 1-hydroxy-2,4,4-trimethylcyclopentanecarboxylic acid with lead dioxide in sulfuric acid,3 by the hydrogenation of 2,4,4-trimethyl-2-cyc.lopentenone, 4 5 by the Clemmensen reduction of dimethyldihydroresorcinol,6 7 by the distillation of powdered 2,4,4-trimethyladipic acid with sodium hydroxide,8 and by the saponification and decarboxylation of ethyl 2-keto-l,4,4-tri-mcthylcylopentanecarboxylate.9 10 The rearrangement of iso-phorone oxide 11 appears to represent the optimum combination of favorable yield and convenient procedure. 

More definite evidence for the transient existence of the un-cyclized l-(jS-aminoethyl)-3,4-benzoquinones has been obtained recently by Kodja and Bouchilloux,77 78 who noted that a transient yellow color (Amax ca. 385 mp) was occasionally observed during the enzymic oxidations of catecholamines (particularly in unbuffered systems at low temperatures). This phenomenon was probably due to the formation of the transient o-quinones. (The absorption maximum of o-benzoquinone, the effective chromophore of the open-chain quinones, is known to occur at ca. 390 mp.79) An absorption maximum at 390 mp is characteristic of the formation of the dopa-quinone chromophore during oxidation of small C -terminal tyrosine peptides in the presence of tyrosinase.37 48 Similar spectroscopic features were observed when the oxidations were carried out with lead dioxide in sulfuric acid solutions (pH> 1). If the initial oxidation was carried out for a short period of time, it was possible to regenerate the original catecholamines by reduction (e.g. with sodium bisulfite, potassium iodide, and zinc powder) and to show that the 385 mp peak disappeared.77,78 Kodja and Bouchilloux were also able to identify 2,4-dinitrophenylhydrazones of several of the intermediate non-cyclized quinones by paper chromatography and spectroscopy (Amax n weakly acid solution ca. 350 mp with a shoulder at ca. 410 mp).77,78... 

Aqueous solutions of normal alkali sulphites are oxidised to dithionate by heating with lead dioxide,1 the latter being reduced to red lead. Manganese dioxide does not react in this way. 

Acenaphthenol has been prepared in poor yield by the oxidation of acenaphthene with lead dioxide 2 and it is among... 

Isatin, JV-methylisatin, and JV-hydroxyisatin can be reduced to semidiones by treatment with the enolate anion of propiophenone in dimethylsulfoxide.258 Nitroxides are prepared from iV-hydroxyisatin by treatment with lead dioxide in dioxan, while another nitroxide was formed spontaneously from iV-hydroxyisatin in basic dimethyl sulfoxide solution in the presence of oxygen.256... 

Autoxidation of 3-aminoindoles leads to the formation of the diimino derivative of indigo, whilst controlled oxidation of 3-amino- and 3-alkylamino-indoles with lead dioxide yields the corresponding monomeric 3-imino-3/f-indoles <72HC(25-2)537). 

---