Anodic oxidation potentials of aromatic cyanoesters

Using cyclic voltammetry, the anodic oxidation potentials for a series of 15 substituted aromatic cyanoesters have been measured and analyzed. Irreversible anodic oxidations were observed, in addition to a cathodic reduction wave. The different aromatic species exhibited different potential values, in accordance with the type of the substituent and nature of the aromatic nucleus.

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Anodische Oxidationspotentiale aromatischer Cyanoester (Kurze Mitteilung)

Zusammenfassung Unter Verwendung von cyclischer Voltametrie wurden die anodischen Oxidationspotentiale einer Serie von 15 substituierten aromatischen Cyanoestern gemessen und analysiert. Zusätzlich zu einer kathodischen Reduktionswelle wurden irreversible anodische Oxidationen beobachtet. Dabei zeigten die verschiedenen Verbindungen je nach dem Substitutionstyp und der Natur des aromatischen Kerns unterschiedliche Potentialwerte.

     

Anodic oxidation of ring A-aromatic steroids. Cyanation of the aromatic nucleus

The electrochemical oxidation of 3-methoxy-estra-1,3,5(10)-triene-17-one I in methanolic sodium cyanide solution leads to ring A-substitution products II and III and to the addition product IV. This method represents a new way for the direct introduction of a carbon substituent into position 10 of steroids.     

Cerium catalyzed persulfate oxidation of polycyclic aromatic hydrocarbons to quinones

A practical synthesis of polycyclic quinones from the parent hydrocarbons is described. The twophase oxidation of hydrocarbons was accomplished by using ammonium persulfate in the catalytic presence of cerium ammonium sulfate, silver nitrate, and sodium dodecyl sulfate. The reaction conditions and scope have been discussed in detail.     

Ozone oxidation of surface-adsorbed polycyclic aromatic hydrocarbons: role of PAH-surface interaction

The heterogeneous chemistry of surface-adsorbed polycyclic aromatic hydrocarbons (PAHs) plays key roles in nanoscience, environmental science, and public health. Experimental evidence shows that the substrate can influence the heterogeneous oxidation of surface-bound PAHs, however, a mechanistic understanding of the role of the surface is still lacking. We examine the effects of the PAH-substrate interaction on the oxidation of surface-adsorbed anthracene, pyrene, and benzo[a]pyrene by ozone (O(3)) using density functional theory. We find that some O(3) oxidation mechanisms for these planar PAH molecules lead to nonplanar intermediates or products, the formation of which may necessitate partial desorption or "lift-off" from a solid substrate. The energy penalty for partial desorption of each PAH from the surface is estimated for four different substrate types on the basis of literature data and accounted for in the thermodynamic analysis of the reaction pathways. We find that the attractive PAH-substrate interaction may render oxidation pathways involving nonplanar intermediates or products thermodynamically unfavorable. The influence of the PAH-substrate interaction could contribute in part to the variations in PAH oxidation kinetics and product distributions that have been observed experimentally. Our choice of test molecules enabled us to identify trends in reactivity and product formation for four types of potentially reactive site (zigzag, armchair, bridge, and internal), allowing us to infer products and mechanisms of O(3) oxidation for PAHs of larger sizes. Implications for atmospheric chemistry and the stability of graphene in the presence of O(3) are discussed.     

Anodic oxidation of sodium-O-cyclohexylphosphonite

The research data on the anodic oxidation of sodium salt of cyclohexyl ester of hypophosphorous acid on a Pt electrode are shown. The molecule of this salt has two electroactive centers: phosphoryl (PONa) and phosphine (P-H).     

Selective electrochemical oxidation of aromatic hydrocarbons and preparation of mono/multi-carbonyl compounds

A selective electrochemical oxidation was developed under mild condition.Various mono-carbonyl and multi-carbonyl com-pounds can be prepared from different arom...     

Hydroxyaminomethylation of aromatic hydrocarbons

Conclusions The electrophilic hydroxyaminomethylation of aromatic hydrocarbons was accomplished for the first time, with toluene and m-xylene as examples.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1135–1136, May, 1967.     

Sonochemiluminescence of aromatic hydrocarbons

Multibubble sonoluminescence of water and a series of aromatic hydrocarbons, viz., benzene, toluene, ethylbenzene, and m-xylene (at 25 °C), and a naphthalene melt (at 110–120 °C) was studied. An analysis of the influence of oxygen and argon on the sonoluminescence intensity and the luminescence spectra of these liquid compounds, as well as the effect of additives of ionol, ethanol, and 9,10-dibromoanthracene on m-xylene sonoluminescence, showed that a considerable contribution to the sonoluminescence of aromatic hydrocarbons is made by chemiluminescence reactions associated with their oxidation. This sonochemiluminescence is observed in both the gas phase of cavitation bubbles and the bulk solution where luminescence is retained for a long time after ultrasonication switching-off (the initial intensity of the residual chemiluminescence is up to 10% of the luminescence intensity during sonolysis). As for thermoinitiated oxidation, the afterglow of m-xylene contains the radical and molecular components.     

Chemiluminescence in O2 oxidation of organosodium compounds of polycyclic aromatic hydrocarbons and benzophenone

Chemiluminescence (CL) in oxidation of organosodium compounds by O₂ in THF was studied. Emitters of CL are excited complexes of polycyclic aromatic hydrocarbons, excimers¹(R·R)^*. The mechanism of their formation was proposed. The Na⁺, R^.−+O₂ CL system is a unique source for the selective generation of excimers of aromatic hydrocarbons. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 284–288, February, 1997.     

Direct synthesis of phenols by iron-catalyzed biphasic oxidation of aromatic hydrocarbons with hydrogen peroxide

The hydroxylation of a series of aromatic hydrocarbons with hydrogen peroxide, catalyzed by iron complexes with pyrazine-3-carboxylic acid N-oxide, was investigated, operating in a biphasic reaction medium.

The new catalyst showed a high selectivity to the corresponding phenols, minimizing the over-oxidation reactions to polyoxygenated derivatives and tars which, along with dimers formation, are the major limitations of the classical Fenton’s reagent for a practical synthetic application.

In the case of alkylbenzenes, the competitive side chain oxidation at the benzylic positions also occurred. Electron rich substrates, such as anisole, were oxidized with very poor selectivity.

The reactions were carried out in a biphasic system that allows a convenient recovery and recycling of the catalyst by phase separation techniques. The catalyst showed a complete retention of activity after six consecutive reaction cycles.

The new catalyst appears as a promising tool for the direct synthesis of phenols, in alternative to the conventional multi-step methods.     

Catalytic enantioselective oxidation of aromatic hydrocarbons with D4-symmetric chiral ruthenium porphyrin catalysts

The [Ru^II(D₄-Por¹)(CO)(MeOH)] (D₄-H₂Por¹ = tetrakis[(1S,4R,5R,8S)-1,2,3,4,5,6,7,8-octahydro-1,4:5,8-dimethanoanthracen-9-yl]porphyrin) complex 1 is an effective catalyst for asymmetric hydroxylation of aromatic hydrocarbons with 2,6-dichloropyridine N-oxide (Cl₂pyNO) as terminal oxidant. Up to 76% ee was achieved for the catalytic hydroxylation of 4-ethyltoluene, 1,1-diethylindan and benzylcyclopropane. Both electron-donating and -withdrawing substituents were found to accelerate the catalytic oxidation reaction, and a large primary H/D kinetic isotope effect (k_H/k_D = 11 at 298 K) was observed for the catalytic ethylbenzene-d₁₀ oxidation. A mechanism involving rate-limiting hydrogen atom abstraction by reactive oxoruthenium species is postulated.