Variable Valence Metals Research Articles

Possible mechanisms of activation of the lipid peroxidation reaction in the vitreous body after hemorrhage

It has been established that one of the mechanisms of lipid peroxidation intensification is mediated by metals of variable valency, hemin compounds and phospholipids carried into the vitreous body by blood.

Catalytic properties of variable-valence metal oxides in the oxidative dehydration of ethylbenzene

1. The greatest activity among Mo, V, Re, U, Cr and W oxides supported on magnesium oxides in the oxidation dehydrogenation of ethylbenzene is found for the vanadium-magnesium system. 2. The nature of the support affects the catalytic properties of the vanadium systems since the coordination and valence state of the vanadium ions depends on the support. 3. The greatest activity is found for the vanadium oxide catalysts containing vanadium (V) ions in octahedral coordination.

Homolytic reactions of functional oxygen-containing compounds initiated by compounds of variable valency metals

Investigations into the liquid phase reactions of functional aliphatic and alicyclic compounds which are initiated by peroxides and UV radiation constitute an important stage along the route of the conversion of free radical chemistry into a powerful instrument of contemporary organic synthesis. The progress made in recent years in the development of this route has been determined by the use of compounds containing variable valency metals for the initiation of homolytic and ion-radical reactions. Such compounds act as oxidants of the reactants and the radicals formed from them. 0ne-electron oxidants, ions, and metal complexes have significantly extended the range of homolytic reactions; they enable one to generate those radicals which cannot be prepared by other methods, and to convert alkyl groups into functional compounds readily.

Effect of manganese on the thermal degradation of hydrocellulose fibres

Mineral contaminants exert a large effect on the intensity of the thermal degradation of cellulose and the composition of the decomposition products. Thereupon the thermal stability of the cellulose depends considerably not only on the overall ash content, but also on its qualitative composition, particularly on the content of metals of variable valence [i]. Thus, an elevated iron content in hydrocellulose (HC) fibre significantly accelerates the processes which take place in heat treatments and which lead to loss of weight and a decrease in degree of polymerization (DP) of the cellulose [2]. In the present article we give the results of a study of the effect of manganese on the thermal and thermo-oxidative degradation of HC fibre. Heat-treatment was carried out under conditions of isothermal heating, in the temperature range 175-240°C, in media of nitrogen, air, and vacuum (13.3 Pa) for 1-3 h. The intensity of the thermal degradation of the cellulose was evaluated from the weight loss of fibre specimens and the decrease in DP of the cellulose, as functions of the Mn content, temperature, and duration of treatment. Viscose tire yarn having various manganese contents, dried to constant weight, and subjected to pyrolysis in the free state served as the object of investigation. Manganese was introduced into the fibre by impregnating it with a

Paramagnetic complexes of 4-trifluoroacetoacetyl-2,2,5,5-tetramethyl-?3-imidazolin-1-oxyl

1. 4-Trifluoroacetoacetyl-2,2,5,5-tetramethyl-Δ3-imidazolin-1-oxyl and its complexes with Cu(II), Co(II), and Eu(III) have been synthesized. 2. On the basis of a study of the magnetic properties of the paramagnetic complexes that have been prepared, it has been established that there is a weak exchange interaction between the unpaired electrons of the nitroxyl fragments and the variable-valence metal ions.

Catalytic ?-alkyation of aldehydes with olefins

1. The catalyticα-alkylatton of aldehydes by olefins has been accomplished in acetic acid containing acetates of transition metals of variable valence, in the presence of oxygen. Based on this reaction,α-alkyl-substituted aldehydes of diverse structure have been synthesized in 30–60% yield on the olefin converted. 2. The selectivity of theα-alkylation depends on the properties of the metal ion as well as its valence state in the course of the reaction. It diminishes in the order: Mn(III) > Co(II) > Mn(II) ∼ Ni (II) > Ce (III) > Cr(III) > Co (III). A mechanism has been proposed for the catalyticα-alkylation of aldehydes in which the key stage is the reaction between an enolate complex of the transition metal and the olefin.

Complex formation between polar components of asphalthene-resin substances of oil and metals of variable valency

Complex formation between polar components of asphalthene-resin substances of oil and metals of variable valency

The sensitized photo-oxidation of aliphatic polyamides

The sensitized photo-oxidation (SPO) of aliphatic polyamides (PA) has been studied on the basis of comparing the kinetic curves of oxygen absorption, the accumulation of peroxides, main chain bond fractures and the comsumption of sensitizers. The quantitative characteristics of the SPO have been determined. The photo-sensitization was carried out by non-chain oxidation with the following compounds: peroxides, aromatic ketones, quinones, phenolic-type anti-oxidants, variable valence metal salts, and xanthene dyes; all these had the same mechanism of photo-degradation of the polymer, and the kinetic curves for bond fracture showed the existance of an induction period. The results have been explained as due to the sensitization of the photo-oxidation by there compounds, which consists of a photo-initiation of the central marco-radical, i.e. ∼CH 2CONHCHCH 2∼ (P 1); this cannot result main chain bond fracture of the PA. The decomposition of the macromolecules is explained by the features of the recombination mechanism of the P 1O 2 peroxide radicals.

The synthesis and properties of chelate forming heterocyclic polyamides the poly(amido)benzoxazoles

Aromatic 6-amino-2(2′-hydroxy-5′- or 4′-aminophenyl)benzoxazoles were polycondensed with terephthalyl chloride at low temperature to poly(amido)arylazoles. The reduced viscosity of these polymers has been found to depend on the chemical composition of the monomers. The produced polymers form intra-complexes with variable valency (transition) metals.

Synthesis and properties of chelate forming heterocyclic polyamides. Polyamido-benzimidazole

High molecular weight polyamido-arylazole was synthesized from aromatic diamine containing a benzimidazole ring and terephthaloyl chloride by low temperature polycondensation. The polymer with chelate forming properties readily forms intracomplex compounds with variable valency metals. A study was made of the effect of the type of metal on the heat resistance of polymers and it was shown that its addition somewhat reduces heat resistance.

New oxidation-reduction systems in the synthesis of graft copolymers of cellulose

New methods of synthesis of graft copolymers using redox systems are discussed. In these the reducing agents are cellulose preparations containing thiocarbonate groups and the oxidizing agents are ions of metals of variable valency (V 5+, Fe 3+, Cr 6+). An analysis is given of specific features of graft copolymerization conducted under heterogeneous conditions using the method of chain transfer from radicals formed by catalytic decomposition of hydrogen peroxide by Fe 2+ ions bound to the cellulose. The problem of increasing the conversion of monomer by carrying out heterogeneous grafting by the method of chain transfer from initiator radicals is discussed. A new method is proposed and illustrated by examples, permitting grafting to be achieved with almost 100% conversion of monomer in some instances.

The study of dehydropolyacenaphthylene (DPA) reactions with variable valence metal naphthenate and lithium ethylate

The study of dehydropolyacenaphthylene (DPA) reactions with variable valence metal naphthenate and lithium ethylate

Oxidation of mesitylene by an ozone-oxygen mixture

1. 1. A study was made of catalytic oxidation of mesitylene by an ozone-oxygen mixture in acetic acid at atmospheric pressure and a temperature of 150°. 2. 2. A system was proposed for main chemical conversions which explains the role of variable valency metals in oxidation of mesitylene by an ozone-oxygen mixture.

Liquid-phase oxidation of 2-methyltetrahydrofuran

1. A study was made of the effect of various organic compounds and salts of variable valence metals on the rate and direction of the oxidation of 2-methyltetrahydrofuran. 2. The highest accumulation rate of the 2-methyltetrahydrofuran hydroperoxides, with a relatively low selectivity, is observed in the presence of 5 · 10−6 M of Co(OCOCH3)2 · 4H2O; a high rate and selectivity of the oxidation process is achieved in the presence of 1 M of (CH3CO)2O.

Reaction of peroxydiglutaric acid with salts of variable valence metals in aqueous solution

1. The decomposition of peroxydiglutaric acid in aqueous solution under the influence of FeSO4 proceeds by the one-electron transfer mechanism, and makes it possible to selectively generate 3-carboxypropyl radicals. 2. The 3-carboxypropyl radicals that are formed in this system are converted into products by three directions: they are cyclized toγ-butyrolactone, dimerized to suberic acid, and they cleave hydrogen to give butyric acid. 3. Water cannot serve as a hydrogen donor for the 3-carboxypropyl radicals; organic compounds function as the substrate here.

Low-temperature conjugated oxidation of saturated hydrocarbons involving salts of variable valence metals

1. A number of simple and comparatively efficient systems was proposed for the oxidation of saturated hydrocarbons in conjugation with the oxidation of a number of metal salts of variable valence, in which connection nearly 100% selectivity in product (either ketone or alcohol) can be achieved in these systems. 2. A study was made of the effect of the individual components of the system on the yield of oxidation products and on the selectivity.

Negative catalysis by salts of variable valence metals in reactions for oxidation of aliphatic amines by molecular oxygen

1. It was found that the salts of the variable valence metals act as negative catalysts in the initiated oxidation of primary and secondary aliphatic amines. The negative catalysis is due to the oxidation-reduction properties of the amino peroxide radicals. 2. The ratios of the rate constants:\({{k(RO_{\dot 2} + MX_n )} \mathord{\left/ {\vphantom {{k(RO_{\dot 2} + MX_n )} k}} \right. \kern-\nulldelimiterspace} k} (RO_2^. + RO_{\dot 2} )\) in cyclohexylamine and di-n-butyl-amine were measured for the salts of Co, Mn, Cu, Fe and Ce.

Investigation of the catalytic activity of certain azaporphin compounds in the oxidation of cumene

1. High initiating activity of azaporphin compounds of metals of variable valence in the oxidation of cumene was detected. 2. The effectiveness of the action of the initiator depends on the nature of the metal and on its content in the polyazaporphin molecule. 3. The high, selectivity of the investigated polyazaporphin compounds does not depend either on the nature of the metal or on its content in the macromolecule and significantly exceeds the selectivity of phthalocyanines.

Reactions of carboxylic acids and their derivatives with compounds of variable valence metals

1. A study was made of the dehydrocarboxylation of some acetoxyalkanoic acids RR'CHCH(COOH) (CH2)nOAc by the joint action of the tetravalent lead and divalent copper acetates in the presence of pyridine. 2. Conditions were found for running the dehydrocarboxylation that assured a high conversion of the acids to the cis- and trans-acetates RR'CH=CH(CH2)nOAc and RR'CHCH=CH(CH2)n-1OAc. 3. The mutual arrangement of the acetoxyl and carboxyl groups and the structure of the RR'CH fragment of the acid exert a substantial influence on the ratio of the formed acetates.

Polymerization of styrene by trichloroacetic acid and salts of variable-valency metals

Polymerization of styrene by trichloroacetic acid and salts of variable-valency metals