Kinetics of photoreduction of 9,10-phenanthrenequinone in the presence of amines and polymethylbenzenes

A study of the kinetics of photoreduction of 9,10-phenanthrenequinone in the presence of hydrogen donors (para-substituted N,N-dimethylanilines and polymethylbenzenes) showed that plots of the quantum yield of photoreduction (_H) and apparent reaction rate constant (k _H) vs. oxidation potential of hydrogen donors are extreme. In the presence of amines, k _H and _H increase, as a whole, whereas they decrease in the presence of polymethylbenzenes. In coordinates _H-G _e (G _e is the change in the free energy of electron transfer) for pairs quinone-H donor, _H increases with G _e approaching to zero. For the amine series, this effect is mainly in the exothermic region of G _e (G _e < 0). For the series of polymethylbenzenes, this increase is observed in the endothermic region (G _e > 0).__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2381–2385, November, 2004.     

Reactions of 3,5-di(tert-butyl)-1,2-benzoquinone with terminal acetylenes in the presence of phosphorus trichloride. ipso-Substitution of the tert-butyl group

The reactions of 3,5-di(tert-butyl)-1,2-benzoquinone with aryl-and alkylacetylenes in the presence of phosphorus trichloride afford 4-aryl(alkyl)-8-tert-butyl-2,6-dichloro-2-oxo-2H-benzo[e][1,2]oxaphosphinines as the major ipso-substitution products of the tert-butyl group by the chlorine atom. 4-Aryl(alkyl)-6,8-di(tert-butyl)-2,5-dichloro-2-oxo-and 4-aryl(alkyl)-6-tert-butyl-2,8-dichloro-2-oxo-2H-benzo[e][1,2]oxaphosphinines were obtained as the minor products. The structures of the stable representatives of this series were confirmed by X-ray diffraction. Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1836–1845, September, 2007.     

New sterically hindered di-o-quinones of the biphenyl series

New di-o-quinones of the biphenyl series, namely, 2,2′-dialkyl-5,5′-di-tert-butylbiphenyl-3,4,3′,4′-diquinones, were synthesized. Their structures were established by IR and NMR spectroscopy. The molecular structure of 2,2′-dimethyl-5,5′-di-tert-butylbiphenyl-3,4,3′,4′-diquinone was established by X-ray structural analysis. The structure is characterized by orthogonal (the torsion angle is 82.9°) mutual arrangement ofo-benzoquinone fragments. ESR studies demonstrated that chemical reduction of diquinone proceeds in four oneelectron stages to form paramagnetic mono- and trianions as intermediates. Quinopyrocatechols, which are intermediates in the synthesis of di-o-quinones, were isolated and characterized. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 4, pp. 804–809, April, 1997.     

Unimolecular photochemistry of 4-thiouracils

Unimolecular phototautomeric reactions in 4-thiouracil, 1-methyl-4-thiouracil and 6-aza-4-thiouracil were studied using the matrix-isolation technique combined with infrared absorption spectroscopy. For monomers of these compounds, isolated in solid argon at 10 K, an intramolecular proton-transfer photoreaction was observed. Upon UV (lambda > 345 nm) irradiation, the initial oxo-thione forms of 4-thiouracils were converted into the corresponding oxo-thiol tautomers. The photogenerated oxo-thiol isomers were identified by comparing their experimental IR spectra with the spectra theoretically calculated at the DFT(B3LYP)/6-311++G(2d,p) level. Good agreement between the observed and predicted pattern of spectral bands allowed a reliable identification. This is the first report on experimental observation of isomeric forms of 4-thiouracils other than the canonical oxo-thione tautomers.     

Synthesis of 10-(N′-phenyl)imidoyl derivatives of phenothiazine,and their reactions with o,o-dialkylthio- and dithiophosphates

Condensation of phenothiazine with phenyl isocyanide dichloride has given 10(N-phenylchloroformimidoyl)phenothiazine, exchange reactions of which with salts of diakylthio- and dithiophosphoric acids result in rearrangement of the initially formed 10-[N-phenyldialkoxy(thio)phosphorylthioformimidoyl]phenothiazines to 10-{N-phenyl-N-[dialkoxy(thio)phosphoryl]thiocarbamoyl}phenothiazines, while reaction with diisopropyl dithiophosphoric acid affords diisopropyl chlorothiophosphate, phenyl isothiocyanate, and phenothiazine. 10-(N-Phenylethoxyformimidoyl)phenothiazine alkylates dithiophosphoric acid to give 10-(N-phenylcarbamoyl)phenothiazine, while N²-phenyl-N¹,N¹-diethyl-(10-phenothiazinyl)formamidine reacts with diisopropyl dithiophosphoric acid, affording the salt N²-phenyl-N¹,N¹-diethyl-(10-phenothiazinyl)formamidinium O,O-diisopropyl dithiophosphate.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2596–2601, November, 1989.     

Synthesis and Acid-Base Properties of α-Aminophosphoryl Compounds

-Aminophosphoryl compounds of the phosphonate, phosphine oxide, and ,-bis(phosphine oxide) series and some of their thiophosphoryl analogs were synthesized. Potentiometric measurements of the pK_a of the conjugate acids revealed an insignificant effect of variation of substituents on the phosphorus, nitrogen, and -carbon atoms on the basicity of the phosphorylated amines. The latter are weak bases. Organophosphorus groups decrease the basicity of the amines by almost 5 pK _a units. The role of the hydrophobic effect and intramolecular H-bonding in the obtained substances was discussed.     

Oxidation of Iron and Nickel with 3,5-Di-<Emphasis Type="Italic">tert</Emphasis>-butyl-1,2-benzoquinone in Coordinating Solvents

The final products of oxidation of iron and nickel with 3,5-di-tert-butyl-1,2-benzoquinone in DMSO were identified, and the formal-kinetics relationships of the process were elucidated. The apparent equilibrium constants, enthalpies, and entropies of adsorption of the reactants on the metal surfaces and the rate constants and activation energies of the reactions were determined.     

ESR study of the reaction of decacarbonyidimanganese with thallium(i) 3,6-di-tert-butyl-o-benzosendquinolate in solutions

The reaction of decacarbonyldimanganese Mu₂(CO)₁₀ (1) With thallium(t) 3,6-di-tert-butyl-o-benzosemiquinolate (2) in solution was studied by ESR spectroscopy. Irradiation of solutions containing1 and2 in organic solvents with visible light at 220–280 K leads totrinuclear MnTlMn complex (3). An analysis of hyperfine structure parameters indicates that3 is a semiquinone complex of thallium. A possible mechanism of the formation of complex3 and its molecular structure was discussed.Translated fromIzveshya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 95–98, January, 1996.     

Oxidation of Group II Metals with 3,5-Di-tert-butyl-1,2-benzoquinone

Kinetic regularities of zinc and cadmium oxidation in systems comprising 3,5-di-tert-butyl-1,2-benzoquinone and dimethylformamide or dimethyl sulfoxide are studied. Thermodynamic parameters of oxidant and ligand adsorption on metal surface are estimated. The oxidation of Group II metals (Be, Ca, Mg, Zn, Cd) with 3,5-di-tert-butyl-1,2-benzoquinone gives metal bis-o-semiquinolates. In the presence of excess metal in the medium of coordinating solvents, diradical products convert to the corresponding catecholate derivatives. It is shown that the dependence of the rates of metal reactions with 3,5-di-tert-butyl-1,2-benzoquinone on the donor number of solvent passes through a maximum. With less active metals, the maximum shifts to more basic ligands.