Effect of ketones on the equilibrium between peroxy radicals carrying the chains of cyclohexanol oxidation with molecular oxygen

The influence of methyl phenyl ketone and diphenyl ketone on the kinetics of cyclohexanol oxidation initiated by cumyl peroxide at 373 K was studied. The ratio of the chain propagation rate constant involving the 1-hydroxy-1-phenylethylperoxy radical to the equilibrium constant of radical dissociation into methyl phenyl ketone and hydroperoxy radical (k _2.3/K′₂ = 900 L² mol^?2 s^?1) was determined by the selective inhibition method.     

Solvent extraction of zirconium from hydrochloric acid solutions by sulphoxides and their mixtures

The solvent extraction of zirconium from HCl solutions by dipentyl sulphoxide (DPSO), dioctyl sulphoxide (DOSO), tributyl phosphate (TBP), and their mixtures in various solvents has been studied. At a given H⁺ strength, the extraction coefficient η of the metal increases with an increase in Cl⁻ activity whereas it is almost independent of H⁺ at constant Cl⁻. Under otherwise identical conditions, η increases with an increase in the extractant concentration but is virtually independent of the metal ion concentration over a wide range. The species extracted are ZrCl₄·DPSO, ZrCl₄·DOSO, and ZrCl₄·2TBP. In the case of mixtures, the slope of the log η−log M extractant plot for one component decreases with an increase in the concentration of the second component, the lines crossing at a common point. Extraction is favoured by solvents of low dielectric constant. It is possible to separate zirconium from thorium and uranium by solvent extraction with sulphoxides.     

Micellar catalytic effects in the oxidation of methyl phenyl sulfide with hydrogen peroxide and the hydrogen peroxocarbonate anion

The kinetics and mechanism of the catalysis by ammonium hydrogen carbonate oxidation of methyl phenyl sulfide with hydrogen peroxide has been investigated. Using the classical pseudo-phase model of micellar catalysis, the basic parameters of the catalytic process have been determined: the binding constants of H₂O₂, the HCO ₄ ⁻ anion, and the substrate to the surface of the micelles, and also the second order rate constants for the oxidation of methyl phenyl sulfide in the micellar phase. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 5, pp. 281–287, September–October, 2006.     

Mechanism of the oxidation of organic sulphides by permanganate ion

The kinetics of the oxidation of number of aryl methyl, alkyl phenyl, dialkyl and diphenyl sulphides by permanganate ion to yield the sulphoxides, have been studied. The reaction is first order with respect to the sulphide and permanganate and is independent of hydrogen ion concentration. The reaction exhibited negative polar reaction constants and a small degree of steric hindrance. The lack of solvent isotope effect and the observed solvent effect ( m = 0.39 for McSPh) are explained by an electrophilic attack of permanganate-oxygen on the sulphide yielding a polar transition state. A moderate anchimeric assistance was observed in the oxidation ofo-C00Me ando-C00H substituted methyl phenyl sulphide. A mechanism involving a one-step electrophilic oxygen transfer from permanganate ion to the sulphide and a polar product-like transition state, has been proposed.     

Effect of substituents on the oxidation of some alkyl-aryl sulphoxides by chloramine-T

The oxidation rates of some substituted phenyl methyl sulphoxides with chloramine-T have been studied in alkaline and neutral media. OsO₄ is used as catalyst in alkaline medium where the meta and para substituents show no effect on the reaction rate. This is explained on the basis of isokinetic relationship. In both the media, the orthosubstituents show steric effect.     

Simulation of the reaction front propagation during co oxidation on Pt (100) under unsteady-state conditions

Acid tetrabutylammonium salts of Ti(IV)-monosubstituted heteropolytungstate, PW₁₁TiO₄₀ ⁵⁻, show high catalytic acitivity in the oxidation of methyl phenyl sulfide with hydrogen peroxide, while the corresponding tetrabutylammonium salts containing no protons are poor catalysts for this reaction.     

Oxidation of methyl phenyl sulfide with hydrogen peroxide catalyzed by Ti(IV)-substituted heteropolytungstate

Alkylammonium salts of Ti(IV)-substituted heteropolytungstate, PW₁₁TiO ₁₀ ⁵⁻ , catalyze the oxidation of methyl phenyl sulfide with hydrogen peroxide. The yield of the corresponding sulfoxide and sulfone is practically quantitative. A³¹P NMR study confirms the formation and reactivity of the PW₁₁O₃₉TiO ₂ ⁵⁻ peroxo complex in organic media.     

The conformational behaviour of some dihydro-1,4-thiazines—III

Oxidation of 1, 3, 5, 13 and 14 by either m-chloroperbenzoic acid or sodium periodate gave single sulphoxides, which are assigned the R configuration. The minor sulphoxide formed by sodium periodate oxidation of 4 and the major sulphoxide obtained in the corresponding oxidation of 6 are assigned the S configuration. The conformational properties of the above sulphoxides have been examined by the NMR method; the derivatives show an overwhelming preference to adopt the conformation with the oxide function in the axial environment.     

Oxidation of methyl phenyl sulfide by carbamide peroxide in the presence of activators

The oxidation of methyl phenyl sulfide by carbamide peroxide in water and water–ethanol mixtures proceeds at the same rates as oxidation by hydrogen peroxide. In the presence of ammonium bicarbonate, the reaction proceeds through a pathway including HCO₄^- as a more active oxidizing agent than H₂O₂.     

Interrelation between the chemical structure and antioxidant properties of N-substituted amides of salicylic acid

The kinetics of the initiated oxidation of a model lipid (methyl oleate has been investigated in the presence of a group of new “hybrid” structures, namely, N-substituted amides of salicylic acid whose structure contains an amide residue conjugated with, or separated by a bridging fragment (three methylene groups) from, an N-phenolic substituent. The compounds also differ in the degree of screening of the OH groups. The process was initiated by thermal decomposition of azobisisobutyronitrile at 60°C (initiation rate of w _i = 4.2 × 10⁻⁸ mol L⁻¹ s⁻¹) or by UV irradiation (γ = 313−365 nm, w _i = 0.6 × 10⁻⁸ mol L⁻¹ s⁻¹). The compounds examined exhibit antiradical activity owing to the presence of the phenolic hydroxyl groups. N-substituted salicylamides efficiently inhibit the overall methyl oleate oxidation process and are comparable in activity with dibunolum and α-tocopherol or are superior to them. The structures in which the residues of salicylamide and sterically hindered phenol are separated by the bridging fragment are particularly efficient. The advantages of the salicylamides absorbing at 300–365 nm manifest themselves in UV-initiated oxidation. The peroxidase activity of the N-substituted salicyl acid derivatives is determined by the structure of the amide moiety. The compounds examined here are new, promising, effective antioxidants, whose particular structural fragments act via different mechanisms in oxidation.     

Etude en Résonance Magnétique Nucléaire du Carbone-13 de Quelques Aminopyrazoles. Sur le Problème de la Détermination des Constantes d'Equilibre Tautomère

The ¹³C chemical shifts of 32 pyrazoles were measured in hexadeuterated dimethyl sulphoxide and in hexamethylphosphorotriamide. Substituent effects (methyl and amino groups on the pyrazolic carbons, and methyl, n-butyl and phenyl groups on the nitrogen) were calculated by multilinear regression analysis. The general problem of the ¹³C NMR study of annular tautomerism in azoles is discussed and illustrated by the 3(5)-aminopyrazole case.     

Study of chemical processes in the modification of epoxide polymers by aluminum oxide

The processes occurring during the modification of epoxy polymers by various polymorphic aluminum oxide modifications (γ-AlO(OH), γ-Al₂O₃, α-Al₂O₃) with epoxy groups were studied by the methods of IR Fourier spectroscopy, chemical analysis, and differential scanning calorimetry (DSC) by an example of a model compound (phenyl glycidyl ether). Two types of interactions were revealed: a direct chemical reaction of phenyl glycidyl ether with the surface hydroxy groups of alyminum oxide, and phenyl glycidyl ether homopolymerization. By processing by graphical method the data of chemical analysis on the diminishing in amount of epoxy groups in the course of the polycondensation reaction the value of activation energy 106–110 kJ mol⁻¹ of the process of phenyl glycidyl ether interaction with aluminum γ-oxide was determined.     

Triaryl- and trialkylantimony(V) Bis(catecholates) based on 1,1′-spirobis[3,3-dimethylindanequinone-5,6]: Spectroscopic and electrochemical studies

A series of new binuclear bis(catecholate) antimony(V) complexes based on 1,1′-spirobis[3,3-dimethylindanequinone-5,6] with various substituents at the central antimony atoms, R₃Sb(Cat-Spiro-Cat)SbR₃ (I–IV) and R₃Sb(Cat^Br-Spiro-^BrCat)SbR₃ (V–VIII) (R = p-fluorophenyl, phenyl, p-tolyl, and ethyl), were synthesized. Spirobis(catecholates) I–III exhibit two one-electron oxidation waves on the cyclic voltammograms, whereas bromo-substituted spirobis(catecholates) V–VII undergo two-electron oxidation immediately at the first stage. The two-electron oxidation of the complexes results in the loss of one of the organoantimony fragments and the formation of mononuclear catecholate-quinone complexes (Q-Spiro-Cat)SbR₃ or (Q^Br-Spiro-^BrCat)SbR₃, respectively. An insignificant delocalization of the charge and spin between two redox centers is observed in the complexes. The nature of substituents at the antimony atom exerts an effect on the values of redox potentials of the complexes: more donating groups decrease the oxidation potentials of the catecholate fragments and more withdrawing groups increases these values.     

Oxidation of organic sulfides and disulfides with a tert-butyl hydroperoxide-aluminum tri-tert-butoxide system

Methyl phenylethynyl and phenyl phenylethynyl sulfides are selectively converted into methyl phenylethynyl and phenyl phenylethynyl sulfones, respectively, under the action of system tert-butyl hydroperoxide-aluminum tri-tert-butoxide in benzene at 20 °C. The analogous oxidation of diphenyl disulfide results in S-phenyl benzenethiosulfonate.     

Synthesis and oxidation of sulfides containing an isocyanurate fragment

The reaction of 1-(ω-haloalkyl)-3,5-dimethylisocyanurates with sodium salt of methyl thioglycolate afforded the corresponding 1-[ω-(methoxycarbonylmethylthio)alkyl]-3,5-dimethylisocyanurates, the oxidation of which with the system 34% aqueous H₂O₂-0.2 M NaHCO₃-Mn^II leads to the corresponding sulfones. The oxidation of these compounds with 34% aq. H₂O₂ in Ac₂O gives alternative products, viz., sulfones, sulfoxides, or α-acyloxy sulfides, depending on the temperature and number of methylene groups between the isocyanurate fragment and the sulfur atom.     

配合物(ArO)2Yb(NPh2)2K(THF)4(Ar=C6H2-t-Bu3-2,4,6)的合成、分子结构和催化行为

Reaction of anhydrous YbC13 with 2 equiv, of sodium 2,4,6-tri-tert-butylphenoxide (ArONa, Ar=C6H2-t-Bu3-2,4,6) and 2 equiv, of potassium diphenyl amide in THF afforded the first bis(aryloxo) amido-lanthanide complex of (ArO)2Yb(NPh2)2K(THF)4 (1). In 1, the ytterbium and potassium were bridged via diphenyl amido ligands.The ytterbium metal center was coordinated to two oxygen atoms of aryloxide ligands and two nitrogen atoms of diphenyl amido ligands in a conventional distorted tetrahedral fashion, while the potassium interacted in η^2-fashion with two phenyl rings of the diphenyl amido ligands besides four THF molecules. 1 displayed moderate catalytic activities for the polymerization of methyl methacrylate and acrylonitrile.     

STUDIES ON THE STEREOMECHANISM OF THE REACTION OF SULPHIDES WITH CHLORAMINE-T

Abstract

In the reactions of sulphides (RQS) with chlaramine-T (TsNClNa) sulphilimines (RQSNTs) and sulphoxides (RQSO) are known to be produced from a chlorosulphonium-sulphon-amidate ion-pair intermediate (RQSC1⁺, TsNH^?) in fast competitive S_N reactions of different steric controll. The stereomechanism was investigated in reactions of sulphides (RQ?S) with asymmetric carbon atom adjacent to sulphur, leading to diastereomeric sulphilimines (RQ?S?NTs) and sulphoxides (RQ?S?O). The proportions and the configurations of the diastereomers of both products were determined. The efficiency of the asymmetric induction was found to depend on the bulkiness of the substituents of sulphides. The major diastereomeric components of the produced sulphilimines and sulphoxides proved to have opposite configurations about sulphur. On this basis, the hydrolysis of chlorosulphonium ion yielding sulphoxide is assumed to proceed through a sulphurane intermediate via an a-a type ligand exchange, while the formation of sulphilimine from chlorosulphonium -sulphonamidate ion-pair may involve an a-e type displacement.     

Iodine/DMSO promoted oxidation of benzylic Csp3–H bonds to diketones – A mechanistic investigation

This article describes a mechanistic investigation into the I₂/DMSO mediated benzylic C_sp³–H oxidation of an α-methylene ketone. The electron paramagnetic resonance (EPR) spectrum centred at g = 2.0011 supports the involvement of iodine and benzylic radicals, as the α-iodinated compound 2-iodo-1,2-diphenylethanone was isolated as a key reactive intermediate. The oxidation reaction relies, primarily, on DMSO as a source of oxygen in benzil, proven by the reaction of benzyl phenyl ketone with diphenyl sulfoxide (DPSO).