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111.
A. A. Krolevets I. S. Dolodonov V. V. Antipova I. V. Martynov 《Russian Chemical Bulletin》1992,41(1):153-157
The reactions of alkoxydimethylsilyl cyanides with some tetracoordinated phosphorus chlorides and fluorides were investigated. It was shown that the investigated reactions are realized primarily with the replacement of two halogen atoms by functional groups. The transformations of the phosphorus acid cyanides obtained with metal fluorides were studied.For previous communication, see [1].Institute of Physiologically Active Substances, Russian Academy of Sciences, 142432 Chernogolovka. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 187–191, January, 1992. 相似文献
112.
Theodor H. G. Hehenkamp 《Mikrochimica acta》1992,107(3-6):273-277
In order to optimize the physical properties of HTSC small single crystals grown from a melt for basic studies of their physical properties the influence of the environment on their impurity content was investigated by EPMA. This requires quantitative analysis of all elements being present in the crystals. The accuracy of results was affected by problems with the choice and quality of standards, by contamination but also by malfunction of microprobe electronics. The HTSC materials were found to react with mills, milling balls, crucibles and the atmosphere. These problems are being discussed and some reactions being studied for Y1Ba2Cu3O6+x (0 < x < 1) HTSC in A12O3 and ZrO2 crucibles. The crystals grown contain reproducible amounts of impurities depending on boundary conditions and exhibit a zone structure in composition particularly for Y and Ba within their range of homogeneity. 相似文献
113.
114.
Marta Martino Andrea Salvadori Federico Lazzari Lorenzo Paoloni Surajit Nandi Giordano Mancini Vincenzo Barone Sergio Rampino 《Journal of computational chemistry》2020,41(13):1310-1323
The virtual-reality framework AVATAR (Advanced Virtual Approach to Topological Analysis of Reactivity) for the immersive exploration of potential-energy landscapes is presented. AVATAR is based on modern consumer-grade virtual-reality technology and builds on two key concepts: (a) the reduction of the dimensionality of the potential-energy surface to two process-tailored, physically meaningful generalized coordinates, and (b) the analogy between the evolution of a chemical process and a pathway through valleys (potential wells) and mountain passes (saddle points) of the associated potential energy landscape. Examples including the discovery of competitive reaction paths in simple A + BC collisional systems and the interconversion between conformers in ring-puckering motions of flexible rings highlight the innovation potential that augmented and virtual reality convey for teaching, training, and supporting research in chemistry. 相似文献
115.
A combinatorial approach was applied to devise a set of reference Si–C–O–H species that is used to derive group-additivity values (GAVs) for this class of molecules. The reference species include 62 stable single-bonded, 19 cyclic, and nine double-bonded Si–C–O–H species. The thermochemistry of these reference species, that is, the standard enthalpy of formation, entropy, and heat capacities covering the temperature range from 298 to 2000 K was obtained from quantum chemical calculations using several composite methods, including G4, G4MP2, and CBSQB3, and the isodesmic reaction approach. To calculate the GAVs from the ab initio based thermochemistry of the compounds in the training set, a multivariable linear regression analysis is performed. The sensitivity of GAVs to the different composite methods is discussed, and thermodynamics properties calculated via group additivity are compared with available ab initio calculated values from the literature. 相似文献
116.
Yunwen Tao Zheng Pei Nicole Bellonzi Yuezhi Mao Zhu Zou Wanzhen Liang Zhibo Yang Yihan Shao 《International journal of quantum chemistry》2020,120(6):e26123
In the modeling of spin-crossing reactions, it has become popular to directly explore the spin-adiabatic surfaces. Specifically, through constructing spin-adiabatic states from a two-state Hamiltonian (with spin-orbit coupling matrix elements) at each geometry, one can readily employ advanced geometry optimization algorithms to acquire a “transition state” structure, where the spin crossing occurs. In this work, we report the implementation of a fully-variational spin-adiabatic approach based on Kohn-Sham density functional theory spin states (sharing the same set of molecular orbitals) and the Breit-Pauli one-electron spin-orbit operator. For three model spin-crossing reactions (predissociation of N2O, singlet-triplet conversion in CH2, and CO addition to Fe(CO)4), the spin-crossing points were obtained. Our results also indicated the Breit-Pauli one-electron spin-orbit coupling can vary significantly along the reaction pathway on the spin-adiabatic energy surface. On the other hand, due to the restriction that low-spin and high-spin states share the same set of molecular orbitals, the acquired spin-adiabatic energy surface shows a cusp (ie, a first-order discontinuity) at the crossing point, which prevents the use of standard geometry optimization algorithms to pinpoint the crossing point. An extension with this restriction removed is being developed to achieve the smoothness of spin-adiabatic surfaces. 相似文献
117.
Diana R. Diniakhmetova Anna K. Friesen Sergey V. Kolesov 《International journal of quantum chemistry》2020,120(18):e26335
We have investigated the stepwise addition of four growing methyl methacrylate (MMA) radicals to C60 fullerene, taking into account all possible types of the formed adducts. This reaction set is a reliable approximation for understanding the MMA polymerization process in the presence of C60 fullerene. We have analyzed the structures of the fullerene-MMA adducts and energy parameters of their formation (heat effects and activation enthalpies). We found that up to three MMA growing radicals are favorably attached to C60 as the fullerene-MMA trisadduct is a stable radical of the allyl type. It is inactive for further radical addition, and the elimination of the hydrogen atom from the growing MMA radical becomes preferable. The effects of steric factors and structures of the products of multiple growing MMA radical additions to C60 on the radical polymerization of MMA in the presence of C60 fullerene are considered. 相似文献
118.
E. M. Afsah M. M. Abou-Elzahab M. T. Zimaity G. R. Proctor 《Monatshefte für Chemie / Chemical Monthly》1984,115(8-9):1065-1070
When -keto-ester1 a was reacted with dimethyl acetylenedicarboxylate ring expansion occurred to give substituted cyclooctadienones.Michael reactions of the title compounds1 with unsaturated ketones gave adducts, some of which underwent further cyclization reactions. A new route to -tetralone ring system10 via cyclization of the intermediateMichael adduct9 is described.
Michael- und Ringerweiterungsreaktionen von 6-Carboethoxy-3,5-diaryl-2-cyclohexen-1-onen
Zusammenfassung Bei der Reaktion von -Keto-ester1 a mit Dimethyl-acetylendicarboxylat wurden unter Ringerweiterung substituierte Cyclooctadienone erhalten. DieMichael-Reaktion der Titelverbindung1 mit ungesättigten Ketonen ergab Addukte, von denen einige weitere Cyclisierungsreaktionen eingingen. Es wird ein neuer Weg zum -Tetralonsystem10 über die Cyclisierung des intermediärenMichael-Addukts9 beschrieben.相似文献
119.
Kento Imanishi Benny Wahyudianto Dr. Tatsuhiro Kojima Dr. Nobuto Yoshinari Prof. Takumi Konno 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(8):1827-1833
Here a unique single-crystal-to-single-crystal (SCSC) transformation of a 116-nuclear AuI72CdII40NaI4 cage-of-cage ( 2 CdNa) is reported, which was created from a trigold(I) metalloligand with d -penicillamine by way of a 9-nuclear AuI6CdII3 cage ( 1 ). Cage-of-cage 2 CdNa is composed of 12 cages of 1 that are linked by 4 Cd2+ and 4 Na+ ions, with its surface being covered by 12 NO3− ions to form a discrete, spherical molecule with a diameter ca. 4.7 nm. In crystal 2 CdNa, the cage-of-cage molecules are packed in a cubic lattice with a huge cell volume of ca. 4.5×105 Å3, so as to have large interstices with diameters of more than 3 nm. Upon soaking crystals 2 CdNa in aqueous Cu(NO3)2, all Cd2+ and Na+ were quickly exchanged by Cu2+ to produce an analogous AuI72CuII44 cage-of-cage ( 2 Cu) in a SCSC manner. Prolonged soaking led to the SCSC transformation to another supramolecular structure ( 2′ Cu) consisting of 152-nuclear AuI72CuII80 cage-of-cages that are alternately H-bonded with the AuI72CuII44 cage-of-cages. 2′ Cu showed the accommodation of MoO42− and the conversion of MoO42− to β-Mo8O264− in the crystal, with retention of single-crystallinity. 相似文献
120.
Kapil Mohan Saini Rakesh K. Saunthwal Sushmita Akhilesh K. Verma 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(5):1017-1021
Transition-metal-free regioselective synthesis of functionalized amino-indenones by the reaction of ortho-alkynylaldehydes with a broad range of primary amines by intramolecular cyclization has been described. The designed reaction proceeds through KOH-mediated Prins-type cyclization and DMSO-promoted oxidation of the cyclopent-2-en-1-one system. The proposed mechanism and role of solvent were well supported by control experiments. For the first time, we have disclosed the reverse reactivity of (2-alkynyl)-arylaldimines in a super basic system. 相似文献