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841.
V. Ya. Vorob'eva V. A. Bondarenko E. E. Mikhlina K. P. Turchin L. F. Linberg L. N. Yakhontov 《Chemistry of Heterocyclic Compounds》1977,13(10):1098-1104
The salts and quaternary derivatives of 2-methylene-3-hydroxyquinuclidine readily add nucleophilic reagents because of the high polarity and polarizability of the carbon-carbon double bond, which are due to the overall electron-acceptor effect of the positively charged nitrogen atom and the carbonyl group. The double bond is substantially deactivated in the base, and the addition of nucleophilic reagents is hindered.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1370–1376, October, 1977. 相似文献
842.
Ohne Zusammenfassung 相似文献
843.
844.
Corrosion of iron in slightly acidified sodium sulphate solutions (mainly pH 4.5) in the open air was studied with a rotating disk electrode method at room temperature.Microscopic observations of corroded iron disk surfaces in the pH 4.5 solution revealed that iron initially corrodes locally with the formation of round pits of 10–30 μm in diameter and of(0.6–1.3) × 103 in number per apparent square centimetre followed by the U-shaped brown protective wall formation of precipitates (rust) outside the pits. Each protective wall is formed along the lines of flow of the solution adjacent to the iron surface and each pit is located near the upstream end of the wall. Steady state of corrosion sets in when the parts of surface area surrounded by the wall are completely covered with a microscopically non-porous rust film.The amount of iron in the rust film and the total amount of corrosion of iron including that in the film increase parabolically with the increase in the time of immersion. The amount of iron in the film increases in proportion to the total amount of corrosion independently of the speed of rotation of the disk electrode even in the steady state.The fraction of area of iron surface not covered with the film decreases with time and reaches a certain fixed value in the steady state: the value is smaller at higher rotational speed. The corrosion rate is proportional to the uncovered area, as the corrosion is near the steady state. The pH of the bulk solution increases as corrosion progresses.The corrosion rate of iron can be well interpreted by assuming that the rate is controlled by the diffusion of oxygen from the bulk solution to the surface of iron and that the rust film on iron impedes the diffusion of oxygen. 相似文献
845.
846.
Russian Chemical Bulletin - 相似文献
847.
N. K. Ostrovskaya A. F. Mironov R. P. Evstigneeva N. A. Preobrazhenskii 《Chemistry of Heterocyclic Compounds》1969,5(4):470-473
A method is proposed for the synthesis of porphyrins based on the cyclization of a tetrapyrrole system with methyl and formyl groups at the ends of the molecule. The synthesis of mesoporphyrin IX and diacetyldeuteroporphyrin IX has been effected. 相似文献
848.
849.
G. R. Yurchenko A. K. Matkovsky A. P. Shimansky 《Reaction Kinetics and Catalysis Letters》1993,50(1-2):163-167
Differential isosteric adsorption heats and entropies of adsorption of both n-pentane and diethyl ether on hydrated and dehydrated surfaces of pyrogenic alumina (S=140 m2/g) in the coverage range of 0.15–1.0 have been calculated from the adsorption isotherms. 相似文献
850.
I. V. Katal'nikov V. A. Kuz'min P. P. Levin K. de Jonge G. R. Myul'man 《Russian Chemical Bulletin》1989,38(8):1758-1760
The spectrokinetic indices of the triplet states of nitroaromatic amides were established. The quenching of triplet states by tertiary aromatic amines in apolar solvents leads to the formation of triplet exciplexes. A charge transfer state makes the major contribution to the structure of these exciplexes. Hydrogen atom transfer proceeds efficiently in the case of secondary aromatic amines, leading to the formation of the corresponding neutral radicals.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1912–1915, August, 1989. 相似文献