共查询到20条相似文献,搜索用时 15 毫秒
1.
Nazarov A. M. Khursan S. L. Chainikova E. M. Komissarov V. D. 《Russian Chemical Bulletin》2002,51(4):608-615
The kinetics of the reactions of acetic, benzoic, formic, oxalic, malic, tartaric, trifluoroacetic, and hydrochloric acids with diphenylcarbonyl oxide Ph2COO was studied. The carbonyl oxide Ph2COO was generated by flash photolysis of diphenyldiazomethane Ph2CN2 in solutions of acetonitrile and benzene at 295 K. The apparent rate constants of the reaction range from 4.6·108 for (COOH)2 in MeCN to 7.5·109 L mol–1 s–1 for acetic acid in a benzene solution. The reaction mechanism was proposed, according to which at the first stage the carbonyl oxide is reversibly solvated by the solvent. Then the solvated carbonyl oxide reacts with the acid molecule by the mechanism of insertion at the O—H bond. 相似文献
2.
A. M. Nazarov E. M. Chainikova S. L. Khursan A. N. Ryzhkov R. L. Safiullin V. D. Komissarov 《Russian Chemical Bulletin》1998,47(7):1292-1295
The kinetics of self-termination of benzophenone oxide (BPO) in the liquid phase was studied by flash photolysis. The extinction
coefficient of BPO (ε) was found to be virtually independent of the solvent nature, ε=(1.9±0.1)·103 L mol−1 cm−1. The rate constant of the BPO self-temination increases from 1.8·107 (MeCN) and 7.4·107 (C6H6) to 1.5·109 (n-decane) and 2.0·109 L mol−1 s−1 (n-pentane) at 293±2 K. Solvation of BPO promotes a polar state of the molecule in MeCN and C6H6. In nonpolar hydrocarbons, a great contribution is made by the biradical structure resulting in an increase in the rate constant
and a shift of the absorption maximum to the long-wave region (from 410 nm in MeCN to 425 nm inn-pentane). In solutions of benzene and acetonitrile, benzophenone oxide reacts with the parent diazo compound with a rate
constant of (2–4)·105 L mol−1 s−1 (293±2 K) along with the self-termination.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1329–1332, July, 1998. 相似文献
3.
A. M. Nazarov S. L. Khursan G. A. Yamilova V. D. Komissarov 《Russian Chemical Bulletin》1999,48(6):1079-1085
The reactivity of 14 aldehydes with diphenylcarbonyl oxide Ph2COO was characterized by thek
33/k
31 ratio. The values ofk
33/k
31 vary from 1.3·10−2 (C6F5CHO) to 1.0 (p-Me2N-PhCHO), 70 °C, acetonitrile as the solvent. A charge transfer complex (CTC) was suggested to be primarily formed during
the reaction. The electronic effects of substituents in the reaction were analyzed using the published data. Carbonyl oxide
reacts with aldehydes as a nucleophile (at the carbon atom of the −CHO fragment to form 1,2,4-trioxolane) and also as an electrophile
(at the aromatic ring with the intermediate formation of CTC). The latter is transformed into either 1,2,4-trioxolane or the
products of oxidation of the phenyl ring.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1090–1096, June, 1999. 相似文献
4.
Formation of (phenyl)(2-thienyl)carbonyl oxide, which has the longest lifetime among known carbonyl oxides, has been registered
by flash photolysis in acetonitrile at room temperature. It is consumed in the pseudomonomolecular reaction with the parent
diazo compound.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 666–668, March, 2008. 相似文献
5.
S. L. Khursan A. M. Nazarov E. M. Chainikova V. D. Komissarov 《Russian Chemical Bulletin》2001,50(5):793-797
The absorption spectra and rate constants of diphenylcarbonyl oxide recombination in a series of solvents and their binary mixtures were determined by flash photolysis. An increase in the solvent polarity causes hypsochromic shift of the maximum in the absorption spectrum of Ph2COO. The analysis of the solvent effect on the recombination rate constant in terms of the four-parameter Koppel—Palm equation shows that the reactivity of carbonyl oxide depends on both specific and non-specific solvations. Quantum chemical B3LYP/6-31G(d) calculations of H2COO and PhHCOO carbonyl oxides as well as the complexes of H2COO with acetonitrile and ethylene in different media were performed using a polarized continuum model. 相似文献
6.
A. M. Nazarov G. A. Yamilova S. L. Khursan V. D. Komissarov 《Russian Chemical Bulletin》1998,47(11):2129-2133
The reactivity of organic compounds (PhH, PhMe, PhF, PhCl, PhOH, PhOEt, PhCHO, Ph2CO, PhCN, Ph2S, Ph2SO, Ph2SO2, andp-Me2C6H4) toward diphenylcarbonyl oxide Ph2COO was characterized by thek
33/k
31 ratio, wherek
33 andk
31 are the rate constants for the reactions of Ph2COO with the arene and diphenyldiazomethane Ph2CN2, respectively. The values ofk
33/k
31 vary from 2.6·10−3 (PhCN) to 0.65 (Ph2S) (70°C, MeCN). The reaction is preceded by formation of a complex with charge transfer from a substrate to Ph2COO. In the reactions with aromatic substances (except for Ph2SO, PhCHO, and Ph2CO), carbonyl oxide behaves as an electrophile.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2197–2201, November, 1998. 相似文献
7.
8.
A. M. Nazarov E. M. Chainikova I. A. Kalinichenko S. L. Khursan R. L. Safiullin V. D. Komissarov 《Russian Chemical Bulletin》1999,48(4):672-676
The decay kinetics of a series of carbonyl oxides (CbO)—4-methylbenzophenone oxide, 2,5-dimethylbenzophenone oxide, 4-chlorobenzophenone
oxide, 2-bromobenzophenone oxide, and acetophenone oxide—were studied by the pulse photolysis technique in acetonitrile, benzene,n-decane, andn-pentane. The absorption spectra were studied, and the absorption coefficients and absolute rate constants of CbO decay were
determined. The absorption maxima observed in the spectra of carbonyl oxides range within 405±25 nm. The decay rate constant
was found to depend on both the CbO structure and the medium.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 677–681, April, 1999. 相似文献
9.
A. M. Nazarov E. M. Chainikova R. L. Safiullin S. L. Khursan V. D. Komissarov 《Reaction Kinetics and Catalysis Letters》1997,61(1):173-174
The rate constants of benzophenone oxide decay measured at 25°C by flash photolysis (FPh) strongly depend on the nature of
the solvent [2k=(2.6±0.3)×107 L mol−1 s−1 in CH3CN, and (2.0±0.2)×109 L mol−1 s−1 in pentane]. 相似文献
10.
Qing Xu 《Tetrahedron letters》2004,45(29):5657-5660
cis-Carbocuperation reaction of monoorganocopper reagent with acetylenic sulfoxides, followed by electrophilic reaction with a variety of electrophiles, provided a regio- and stereoselective method to prepare the versatile polysubstituted vinyl sulfoxides. Sonogashira cross-coupling reaction of the obtained α-iodovinyl sulfoxides with terminal acetylenes was also investigated to afford the versatile conjugate sulfinyl enynes. 相似文献
11.
D. V. Kazakov N. N. Kabal’nova S. L. Khursan V. V. Shereshovets 《Russian Chemical Bulletin》1997,46(4):663-671
The reaction of dimethyldioxirane with cumene (22–52°C) follows a chain-radical mechanism. The kinetic regularities of this
reaction were studied by the chemiluminescence and kinetic UV spectrophotometry methods by monitoring the consumption of dioxirane.
The process is inhibited by oxygen. In the absence of O2, the process is accelerated due to the decomposition of dimethyldioxirane induced by alkyl radicals. In this case, the reaction
occurs according to a complicated kinetic law including the first and second orders with respect to dioxirane. Based on the
kinetics and reaction products, the scheme of the process was proposed.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 694–702, April, 1997. 相似文献
12.
Sulfur ylides generated from the reaction of adamantylidene and phenylcarbene with sulfur substrates
Yuri N RomashinMichael T.H Liu Brian T HillMatthew S Platz 《Tetrahedron letters》2003,44(34):6519-6521
Reaction of adamantylidene and phenylcarbene with ethylthiol, ethylene dithiol, allylethylsulfide, allylphenylsulfide, and trimethylenesulfide involves the formation of a sulfur ylide intermediate, followed by H-migration, 2,3-sigmatropic shift, or ring opening to give sulfides. The sulfur ylide formed in the reaction of phenylcarbene with trimethylenesulfide is directly observed by laser flash photolytic techniques. 相似文献
13.
14.
O. A. Snytnikova P. S. Sherin L. V. Kopylova Yu. P. Tsentalovich 《Russian Chemical Bulletin》2007,56(4):732-738
Photochemical reactions involving kynurenines, viz., molecules present in the eye lens, can result in modifications of the lens proteins and cause a development of a cataract.
The rate constants of the reactions of photoexcited kynurenine with several amino acids and antioxidants contained in the
lens were measured. The most efficient quenchers of triplet kynurenine are amino acids tryptophan and tyrosine, as well as
antioxidant ascorbate. In all cases, the quenching reaction proceeds by the electron transfer mechanism, except for the reaction
with oxygen where transfer of the triplet energy to the oxygen molecule occurs.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 704–710, April, 2007. 相似文献
15.
The decay kinetics of hydrated electron (eaq
−) formed upon photolysis of aqueous solutions of sodium pyrene-1,3,6,8-tetrasulfonate at λ = 337 nm in the presence of phosphate
anions (up to 2 mol L−1) was studied by nanosecond laser-pulse photolysis in a wide range of pH (3.5–10) and ionic strength (I, up to 2 mol L−1) values. At high pH values, where the HPO4
2− ions dominate, the eaq
− decay kinetics depends only slightly on phosphate concentration (rate constant for the reaction is at most 2·105 L mol−1 s−1). The H2PO4
− ions react with eaq
− at a rate constant of 2.8·106 L mol−1 s−1 (I = 0), which increases linearly with the parameter
in accordance with the Debye-Hückel theory. The rate constant for quenching of eaq
− by H3PO4 at pH ≤ 4 decreases linearly with the parameter
due to the secondary salt effect and equals 1.6·109 L mol−1 s−1 at I = 0. The logarithm of the rate constant for quenching of eaq
− by phosphates is linearly related to the number of the O-H bonds in the phosphate molecule.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1277–1280, July, 2007. 相似文献
16.
The kinetics and mechanism of the reaction of C6H5 with CH3CHO have been investigated experimentally and theoretically. The total rate constant for the reaction has been measured by means of the cavity ring-down spectrometry (CRDS) in the temperature range 299-501 K at pressures covering 20-75 Torr. The overall bimolecular rate constant can be represented by the expression k = (2.8 +/- 0.2) x 10(11) exp[-(700 +/- 30)/T] cm3 mol-1 s-1, which is slightly faster than for the analogous C6H5 + CH2O reaction determined with the same method in the same temperature range. The reaction mechanism for the C6H5 + CH3CHO reaction was also explored with quantum-chemical calculations at various hybrid density functional theories (DFTs) and using ab initio high-level composite methods. The theories predict that the reaction may occur by two hydrogen-abstraction and two addition channels with the aldehydic hydrogen-abstraction reaction being dominant. The rate constant calculated by the transition state theory for the aldehydic hydrogen-abstraction reaction is in good agreement with the experimental result after a very small adjustment of the predicted reaction barrier (+0.3 kcal mol-1). Contributions from other product channels are negligible under our experimental conditions. For combustion applications, we have calculated the rate constants for key product channels in the temperature range of 298-2500 K under atmospheric-pressure conditions; they can be represented by the following expressions in units of cm 3mol-1 s-1: k1,cho = 8.8 x 10(3)T2.6 exp(-90/T), k2,ch3 = 6.0 x 10(1)T3.3 exp(-950/T), k3a(C6H5COCH3 + H) = 4.2 x 10(5)T0.6 exp(-410/T) and k3b(C6H5CHO + CH3) = 6.6 x 10(9)T-0.5 exp(-310/T). 相似文献
17.
Time-resolved studies of germylene, GeH2, generated by laser flash photolysis of 3,4-dimethyl-1-germacyclopent-3-ene at 193 nm and monitored by laser absorption, have been carried out to obtain rate constants for its bimolecular reaction with HCl. The reaction was studied in the gas phase, mainly at a total pressure of 10 Torr (in SF6 bath gas) at five temperatures in the range 295–558 K. Experiments at other pressures showed that these rate constants were unaffected by pressure. The second-order rate constants at 10 Torr (SF6 bath gas) fitted the Arrhenius equation: log(k/cm3 molecule−1 s−1)=(−12.06±0.14)+(2.58±1.03 kJ mol−1)/RTln10 where the uncertainties are single standard deviations. Quantum chemical calculations at G4 level support a mechanism in which an initial weakly bound donor-acceptor complex is formed. This can then rearrange and decompose to give H2 and HGeCl (chlorogermylene). The enthalpy barrier (36 kJ mol−1) is too high to allow rearrangement of the complex to GeH3Cl (chlorogermane). 相似文献
18.
Wu Feng Deng Nansheng E. M. Glebov I. P. Pozdnyakov V. P. Grivin V. F. Plyusnin N. M. Bazhin 《Russian Chemical Bulletin》2007,56(5):900-903
The formation of MV•+ radical cations was observed upon the laser flash photolysis of the iron(III) tartrate complex [FeIIITart]+ (1) in the presence of methyl viologen (MV2+). The rate constants of the reactions involving MV•+ were measured. The intramolecular electron trans-fer to form FeII and escape of the organic radical to the solvent bulk upon the photolysis of 1 were proposed.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 866–869, May, 2007. 相似文献
19.
Branka Mihaljevic Branka Medved-Rogina Dusan Razem 《Radiation Physics and Chemistry》1999,55(5-6):593-597
The rate of the reaction of the tert-butoxyl radical (t-BuO√) with Fe2+ was measured using laser flash photolysis of methanolic solutions at room temperature. t-BuO√ were generated by homolytic photodecomposition of di-tert-butyl peroxide. The rate constant for oxidation of Fe2+ with t-BuO√ radicals was studied under pseudo-first order conditions. On the basis of competitive kinetics the quantum yield of oxidation, Φ(Fe3+), was determined as function of Fe2+ concentration by measuring the absorbance of Fe3+ as [FeCl]2+ complex. By using the literature values of the rate constants of relevant competing reactions, the desired rate constant was determined to be 3.0×108 M−1 s−1. 相似文献
20.
The reactivity of carbonyl oxides toward benzaldehyde was characterized by thek
33/k
33 ratio, wherek
33 andk
31 are the rate constants of the reactions of RCOO with PhCHO and diphenyldiazomethane Ph2CN2, respectively. Thek
33/k
31 ratios obtained at 60°C in acetonitrile range from 0.61·10−2 (m-BrPh2CN2) to 20·10−2 (Ph2MeCHO). The reactions are probably preceded by the formation of a charge-transfer complex (CTC) with charge transfer from
aldehyde to RCOO. The carbonyl oxide reacts with aldehydes by both the nucleophilic pathway (at the C atom of the—CHO group
to form 1,2,4-trioxolane) and electrophilic pathway (by the attack at the aromatic ring with the intermediate formation of
CTC). In the latter case, either 1,2,4-trioxolane or oxidation products of the phenyl ring are formed.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 650–654, April, 2000. 相似文献