Peroxo

This is a process of anodic oxidation. The ammonium peroxo-disulphate formed is then hydrolysed and the solution distilled in... 

Aqueous solutions containing titanium(IV) give an orange-yellow colour on addition of hydrogen peroxide the colour is due to the formation of peroxo-titanium complexes, but the exact nature of these is not known. 

The colour sequence already described, for the reduction of van-adium(V) to vanadium(II) by zinc and acid, gives a very characteristic test for vanadium. Addition of a few drops of hydrogen peroxide to a vanadate V) gives a red colour (formation of a peroxo-complex) (cf. titanium, which gives an orange-yellow colour). 

Peroxo- Group. When used in conjunction with the trivial names of acids, the prefix peroxo- indicates substitution of —O— by —O—O—. 

The peroxo species can oxidize other reactants, Hquids, catalyst, or final product in the subsequent coupling reaction. One example of such oxidation is observed in the preparation of triphenylphosphine (13—15). If this reaction is hydrolyzed in air instead of an inert N2 atmosphere, then the amount of triphenylphosphine oxide increases from less than 1 wt % to greater than 15 wt %. 

AH of the commercial inorganic peroxo compounds except hydrogen peroxide are described herein, as are those commercial organic oxidation reactions that are beheved to proceed via inorganic peroxo intermediates. Ozonides and superoxides are also included, but not the dioxygen complexes of the transition metals. 

Peroxosilicates. No sohd peroxosiUcates are known. There is some indirect evidence based on catalytic studies for the existence of peroxosihcates in solution (32,33), but nmr spectra of aqueous solutions of siUcates mixed with hydrogen peroxide give no evidence for peroxo species (34). A peroxohydrate of sodium siUcate, Na SiO 3H202, is well estabhshed (35—37) but has found no appHcation. 

The other group of transition metals comprises those metals that retain d electrons in their normal valence states, eg, Co " and Pp". These metals form peroxides from dioxygen or from hydrogen peroxide. Their colors result from d—d transitions. These peroxo species act as nucleophiles. 

Transition-metal-catalyzed oxidations may or may not proceed via peroxocomplexes. Twelve important industrial organic oxidation processes catalyzed by transition metals, many of which probably involve peroxo intermediates, have been tabulated (88). Even when peroxo intermediates can be isolated from such systems, it does not necessarily foUow that these are tme intermediates in the main reaction. 

Actinide Peroxides. Many peroxo compounds of thorium, protactinium, uranium, neptunium, plutonium, and americium are known (82,89). The crystal stmctures of a number of these have been deterrnined. Perhaps the best known are uranium peroxide dihydrate [1344-60-1/, UO 2H20, and, the uranium peroxide tetrahydrate [15737-4-5] UO 4H2O, which are formed when hydrogen peroxide is added to an acid solution of a uranyl salt. 

On dissolution in water, peroxohydrates Hberate hydrogen peroxide into solution. Some peroxo salts also Hberate hydrogen peroxide when dissolved in water, and before the introduction of x-ray crystallography, compounds within these classes were often confused with each other. 

Peroxidic Compounds. When hydrogen peroxide is added to a solution of titanium(IV) compounds, an intense, stable, yellow solution is obtained, which forms the basis of a sensitive method for determining small amounts of titanium. The color probably results from the peroxo complex [Ti(02)(0H)(H20)J, and crystalline salts such as K2[Ti(02)(S0 2] H20 can be isolated from alkaline solutions. The peroxo ligand is bidentate the two oxygen atoms ate equidistant from the titanium (98). 

The action of hydrogen peroxide on freshly precipitated hydrated Ti(IV) oxide or the hydrolysis of a peroxide compound such as K2[Ti(02)(S0 2] yields, after drying, a yellow soHd, stable below 0°C, of composition TiO 2H2O. There is one peroxo group per titanium, but the precise stmcture is not known. The yellow soHd loses oxygen and water when heated and Hberates chlorine from hydrochloric acid. When freshly prepared, it is stable in acid or alkah, giving peroxy salts. 

Olefin isomerization can be catalyzed by a number of catalysts such as molybdenum hexacarbonyl [13939-06-5] Mo(CO)g. This compound has also been found to catalyze the photopolymerization of vinyl monomers, the cyclization of olefins, the epoxidation of alkenes and peroxo species, the conversion of isocyanates to carbodiimides, etc. Rhodium carbonylhydrotris(triphenylphosphine) [17185-29-4] RhH(CO)(P(CgH )2)3, is a multifunctional catalyst which accelerates the isomerization and hydroformylation of alkenes. 

Aminechromium peroxo-complexes Azides (acyl, halogen, non-metal, organic) Arenediazoniumolates... 

Endless variations have been played on these themes and the B atom can be surrounded by innumerable combinations of groups such as acyloxy (RCOO), peroxo (ROO), halogeno (X), hydrido, etc., in either open or cyclic arrays. However, no new chemical principles emerge. 

In this new type of coordination mode d(O-O) is long (147 pm) and the weakness of the 0-0 linkage is also shown by the very low value of 851 cm for v(O-O), both values being more characteristic of peroxo than of superoxo complexes/ ... 

Figure 14.5 (a) Reaction of Al,Al -ethylenebis(3-Bu -salicylideniminato)cobalt(II) with dioxygen and pyridine to form the superoxo complex [Co(3-Bu Salen)2(02)py] the py ligand is almost coplanar with the Co-O-O plane, the angle between the two being 18°.< (b) Reversible formation of the peroxo complex [Ir(C0)Cl(02)(PPh3)2]. The more densely shaded part of the complex is accurately coplanar. ... 

Figure 14.8 Schematic representation of the planar central portion of the /r-peroxo complex [La N(SiMe3)2)2(OPPh3)]202.

Interest in the production of high-energy oxidizers for use in rocket motors has stimulated the study of peroxo compounds bound to highly electronegative groups during the past few decades. Although such applications have not yet materialized, numerous new compounds of this type... 

Other peroxo compounds SF500C(0)F, SF5OSF4OOSF5, SF5OSF4OOSF4OSF5,... 

The reaction of gaseous SO2 or SO3 with O2 in a silent electric discharge gives colourless polymeric condensates of composition S03+ t (0 < jc < 1). These materials are derived from yS-SO3 by random substitution of oxo-bridges by peroxo-bridges ... 

Monomeric neutral SO4 can be obtained by reaction of SO3 and atomic oxygen photolysis of S03/ozone mixtures also yields monomeric SO4, which can be isolated by inert-gas matrix techniques at low temperatures (15-78 K). Vibration spectroscopy indicates either an open peroxo Cj structure or a closed peroxo C2v structure, the former being preferred by the most recent study, on the basis of agreement between observed and calculated frequencies and reasonable values for the force constants ... 

Peroxodisulfuric acid, H2S2O8, is a colourless solid mp 65° (with decomposition). The acid is soluble in water in all proportions and its most important salts, (NH4)2S208 and K2S2O8, are also freely soluble. These salts are, in fact, easier to prepare than the acid and both are made on an industrial scale by anodic oxidation of the corresponding sulfates under carefully controlled conditions (high current density, T < 30°, bright Pt electrodes, protected cathode). The structure of the peroxo-disulfate ion [now preferably called hexaoxo-/r-peroxodisulfate(2-)]0 l is OaSOOSOa " with... 

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