共查询到20条相似文献，搜索用时 31 毫秒
1.
| 1. | The kinetics of the Cannizzaro reaction of benzaldehyde in aqueous KOH solution have been studied spectrophotometrically, working at 25°C and at concentrations ranging from 19.1 to 37.9%. |
| 2. | Reaction proceeds through the formation of an activated complex consisting of the doubly ionized and the un-ionized forms of benzaldehyde and the hydroxide cation. |
| 3. | The spectrophotometric data and the kinetic data have been combined to give an estimate of the benzaldehyde ionization constant in aqueous KOH solution at 25°C. |
| 4. | Analysis of the kinetic data for benzaldehyde reduction by formaldehyde has shown the activated complex for this reaction to be composed of an un-ionized benzaldehyde molecule and a doubly ionized formaldehyde molecule, with or without participation of the hydroxide cation. |
2.
| 1. | Study has been made of the fragmentation paths in chemical ionization of β-methyl-2,3,4,6-tetra-O-methyl-D-galactopyranoside. |
| 2. | The quasimolecular ions of this compound are capable of successive splitting of one, two, and three methanol molecules, the preferred positions for methoxyl elimination being 1, 3, and 4, respectively. |
3.
| 1. | The results of calculations of the first ionization potentials of the anions of the dihydrides of 3d metals by the discrete variation X method are in good agreement with the available experimental values. |
| 2. | The electron affinities of the MH2 molecules are close to the first ionization potentials of the corresponding anions on account of the small values of the adiabatic corrections, and vary noniaonotonically on passing along the series of 3d metals. |
| 3. | The electron affinity of the dihydrides of the 3d metals always exceeds the electron affinity of the central atom, but varies in parallel with the latter quantity along the series. |
4.
B. A. Arbuzov O. Éxsner A. P. Timosheva V. E. Kataev S. G. Vul'fson A. N. Vereshchagin 《Russian Chemical Bulletin》1976,25(6):1206-1212
| 1. | The dipole moments of the two kinds of C-O bonds in acetals and their analogs are not identical. |
| 2. | In formal molecules and the dimethylketal of acetone the C-O-C-O -C chains have gauche-gauche conformation, with the methyl groups lying on different sides of the O-C-O plane. |
| 3. | The dimethylketal of tetrachlorocyclopentadienone is represented by a mixture of trans-gauche and gauche-gauche conformers. |
5.
R. G. Kostyanovskii V. P. Leshchinskaya R. K. Alekperov G. K. Kadorkina L. L. Shustova Yu. I. Él'natanov G. L. Gromova A. É. Aliev I. I. Chervin 《Russian Chemical Bulletin》1988,37(11):2315-2323
| 1. | An efficient method of aziridine dimer synthesis is presented involving reaction of aziridine with esters of strong organic acids followed by alkaline hydrolysis of the resultant N-acyl derivatives. |
| 2. | New N-acyl and carbamoyl derivatives of aziridine dimer and trimer were synthesized. |
| 3. | Linear and branched isomers of aziridine tetramer and also diastereomers of 2-methylaziridine dimer were isolated and characterized. |
| 4. | An efficient regiospecific synthesis of 2,2-dimethylaziridine dimer and trimer was developed. |
6.
L. A. Rozov Yu. V. Zeifman N. P. Gambaryan Yu. A. Cheburkov I. L. Knunyants 《Russian Chemical Bulletin》1976,25(12):2560-2566
| 1. | Depending on the nature of the substituent in the 2 position, l-fluoro-l-(-hydrohexafluoroisopropyl)ethylenes are dehydrofluorinated to either allenes or 1,3-dienes. |
| 2. | It was shown that allylic substitution is possible in the reactions of perfluoroisobutylene with carbanions; the mutual transformations of the allyl and vinyl isomers were studied. |
| 3. | The perfluoroalkenylation product was obtained when perfluoroisobutylene is reacted with ketene acetal. |
7.
| 1. | N-Ethyl and N-isopropyl-3-piperidones were synthesized and the stereochemistry of their reduction was studied. |
| 2. | The dependenceof stereochemistryof a series of reactions at the carbonyl center on bulk of the substituent on nitrogen was established. |
| 3. | Pure a- and e-epimers of N-ethyl- and N-isopropyl-3-piperidols were separated. |
8.
| 1. | Fragmentation has been studied, and kinetic parameters calculated, for quasimolecular [M+H]+ ion breakdown under chemical ionization in methyl ethers of the desoxyglycosides. |
| 2. | Alteration of the position of the desoxy link in the glycoside molecule brings about an extensive redistribution of fragment ion peak intensities of the CI mass spectra of the desoxyglycosides, with an appreciable alteration in the rate of quasimolecular ion breakdown in the gaseous phase. |
9.
| 1. | A series of C-functional derivatives of (3)-1,2-dicarbaundecaborate was synthesized and some of their properties were studied. |
| 2. | Apparent ionization constants of acids of the (3)-1,2-dicarbaundecaborate series were measured and it was found that they are very weak carboxylic acids. |
| 3. | Upon reaction with excess LiA1H4, under mild conditions the carbonyl, *20c \CH(OH) / \begin{array}{*{20}c} \backslash \\ {CH(OH)} \\ / \\ \end{array} , and CH2OH groups of dicarbaundecaborate ketones and alcohols are reduced to CH2 and CH3 groups, respectively. |
| 4. | The effect of Grignard reagent on ketones and esters of the dicarbaundecarbprate series was studied and it was established that the composition of reaction products depends both on the steric hindrance of the carbonyl group and on the electron-donating effect of the (3)-1,2-dicarbaundecaborate substituent. |
10.
B. A. Arbuzov S. G. Vul'fson G. G. Butenko O. A. Samarina A. B. Teitel'baum A. N. Vereshchagin 《Russian Chemical Bulletin》1976,25(1):75-81
| 1. | The ellipsoids of polarizability of dimethylsulfone, sulfuryl chloride, and methanesulfonyl chloride were determined, and the nonadditivity of the parameters of the bonds in the sulfonyl chloride group was demonstrated. |
| 2. | Substituted methane sulfonyl chloride exist in gauche conformations. |
| 3. | In benzenesulfonyl chloride and a series of its para-substituted derivatives, the aryls are situated in the C-S-Cl plane; the para-nitro group induces a 35° rotation. |
11.
I. V. Anonimova N. A. Chadaeva L. K. Yuldasheva S. G. Vul'fson A. N. Vereshchagin B. A. Arbuzov 《Russian Chemical Bulletin》1976,25(12):2519-2524
| 1. | It has been shown that 2-bromo-l,3,2-dioxaarsenanes exist in chair conformation with axially oriented As-Br bonds. |
| 2. | Polarity and polarizability parameters have been found for the As-O and As-Br bonds in 2-bromo-l,3,2-dioxaarsenanes. |
| 3. | The so-called -effect is stronger in the O2AsBr group than in the O2AsCl group. |
12.
B. A. Glazun R. N. Kurnosova M. M. Dubinin I. V. Zhilenkov S. S. Levchenko 《Russian Chemical Bulletin》1976,25(1):8-11
| 1. | In NaA zeolite a homocharge is formed by charges deposited on the surface of the zeolite from the gas gap between the electrode and the specimen. |
| 2. | The existence of thermoelectret effects has been found in the systems NaA-zeolite -air, NaA-helium, NaA-nitrogen, and NaA-oxygen. |
| 3. | The thermoelectret effects are caused by both the accumulation of charges in the specimen and the adsorption of molecules in the electric field. |
| 4. | A low mobility has been noted for adsorbed molecules in the electret state of the system. |
13.
| 1. | The condensation of 1,2-hydroxylamino oximes with biacetyl leads to 1-hydroxy-2-acetyl-2,4,5,5-tetrasubstituted 3-imidazoline 3-oxides. |
| 2. | When 1-hydroxy-2-acetyl-2,5,5-trimethyl-4-phenyl-3-imidazoline 3-oxide is oxidized the CH3CO group is cleaved to give the 5H-imidazole 1,3-dioxide. |
| 3. | Stable nitroxyl radicals were obtained when the 1-hydroxy-2-oximiaoethyl-2,4,5,5-tetrasubstituted 3-imidazoline 3-oxides are oxidized. |
14.
| 1. | The molecular-sieve properties of a number of synthetic and natural chabazites have been investigated. |
| 2. | Characteristic differences have been revealed in the molecular-sieve properties, thermal stability, and x-ray characteristics between the two groups of the zeolites studied. |
| 3. | A reversal of the molecular-sieve effect on passing from the calcium to the sodium-calcium forms of certain synthetic and natural chabazites has been observed. |
15.
M. M. Dubinin O. Kadlets L. I. Kataeva B. A. Onusaitis 《Russian Chemical Bulletin》1988,37(5):849-854
| 1. | The adsorption properties with respect to benzene vapors and the pore structure of carbon adsorbents with almost maximum development of the microporosity were studied. |
| 2. | The position of the micropore volume distribution curves whose maxima correspond to a size (halfwidth) of 1.2–1.4 nm and micropore volumes 1.5 cm3/g is a characteristic feature of the adsorbents studied. The difference between ordinary active carbons and the active carbons investigated is only quantitative in the values of the parameters of the Dubinin-Stockley adsorption equation. |
| 3. | The adsorption isotherms are described by the adsorption equation from the theory of volume filling of micropores in a wide range of equilibrium relative pressures and temperatures of 293–353 K with totally satisfactory precision. |
| 4. | The question of the upper limit of the micropores of carbon adsorbents is discussed. |
16.
A. M. Moiseenkov V. A. Dragan A. V. Lozanova V. V. Veselovskii 《Russian Chemical Bulletin》1988,37(8):1603-1609
| 1. | Dimethyl, diphenyl, and tetramethylene sulfoxide hydrochlorides react with methylheptenyl, citronellyl, and geranyl acetates to give predominantly the allylic chlorination products. |
| 2. | These findings are preferably to be regarded as involving AdE reactions between the weakly electrophlic hydroxy and (or) chlorosulfonium cation and the trisubstituted C=C bond in these olefins at the key stage. |
| 3. | The addition of lithium perchlorate has been found to accelerate this reaction. |
| 4. | Sulfoxide hydrobromides are highly selective brominating agents for the terminal grouping in isopropenoid oligoolefins. |
17.
V. F. Rudchenko I. I. Cher'vin V. N. Voznesenskii V. S. Nosova R. G. Kostyanovskii 《Russian Chemical Bulletin》1988,37(12):2513-2516
| 1. | For the first time a diastereomerically enriched acyclic NH-dialkoxyamine with asymmetric nitrogen atom in the NH group was obtained. |
| 2. | By low-temperature PMR spectra the diastereomers of a 1,1-dialkoxyurea with asymmetric amid enitrogen atom were observed. |
18.
L. F. Chertanova G. A. Marchenko A. A. Gazikasheva Yu. T. Struchkov V. F. Sopin L. N. Punegova A. S. Mukhametzyanov 《Russian Chemical Bulletin》1989,38(2):250-253
| 1. | The planar alkoxydiazinoxide fragments are shown to have the Z-configuration and be orthogonal to each other by an x-ray structure study of a series of alkoxydiazinoxides. |
| 2. | In the oxydiazinoxide fragments, p- conjugation occurs. |
| 3. | The molecules of the compounds in the crystals studied are joined by hydrogen bonds. |
19.
Presently, a large variety of layered materials are synthesized that are able to intercalate neutral guest molecules or to exchange inorganic and organic ions for interlayer ions. Several of these materials are also found as minerals.The intracrystalline reactivity of a few selected compounds will be described and compared to clay minerals:
相似文献
| – | - intercalation into crystalline silicic acids; |
| – | - reactions of phosphates, arsenates, and sulfates; |
| – | - reactions of titanates, niobates, and molybdates with long chain alkylammonium ions, and |
| – | - anion exchange properties of double hydroxides. |
20.
| 1. | The three-dimensional structure and the distribution of the electronic charges in the molecules of substituted 1-vinyl-pyrazoles were calculated by the MNDO method. It was established that the dipole moment is a good criterion for quantitative determination of the stereochemical position of the vinyl group. |
| 2. | The electronic effect of the CH3 groups corresponds to their positive inductive effect. The NO2 group suppresses the strong negative mesomeric effect and the weaker negative inductive effect. A positive mesomeric effect is characteristic of the Br atom. |
| 3. | In the substituted 1-vinylpyrazoles their electron-donating characteristics are determined by the ionization potentials of the unshared electron pair of the N2 atom. |