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21.
On the long‐range relativistic effects in the 15N NMR chemical shifts of halogenated azines 下载免费PDF全文
Dmitry O. Samultsev Yury Yu. Rusakov Leonid B. Krivdin 《Magnetic resonance in chemistry : MRC》2017,55(11):990-995
Long‐range β‐ and γ‐relativistic effects of halogens in 15N NMR chemical shifts of 20 halogenated azines (pyridines, pyrimidines, pyrazines, and 1,3,5‐triazines) are shown to be unessential for fluoro‐, chloro‐, and bromo‐derivatives (1–2 ppm in average). However, for iodocontaining compounds, β‐ and γ‐relativistic effects are important contributors to the accuracy of the 15N calculation. Taking into account long‐range relativistic effects slightly improves the agreement of calculation with experiment. Thus, mean average errors (MAE) of 15N NMR chemical shifts of the title compounds calculated at the non‐relativistic and full 4‐component relativistic levels in gas phase are accordingly 7.8 and 5.5 ppm for the range of about 150 ppm. Taking into account solvent effects within the polarizable continuum model scheme marginally improves agreement of computational results with experiment decreasing MAEs from 7.8 to 7.4 ppm and from 5.5 to 5.3 ppm at the non‐relativistic and relativistic levels, respectively. The best result (MAE: 5.3 ppm) is achieved at the 4‐component relativistic level using Keal and Tozer's KT3 functional used in combination with Dyall's relativistic basis set dyall.av3z with taking into account solvent effects within the polarizable continuum solvation model. The long‐range relativistic effects play a major role (of up to dozen of parts per million) in 15N NMR chemical shifts of halogenated nitrogen‐containing heterocycles, which is especially crucial for iodine derivatives. This effect should apparently be taken into account for practical purposes. 相似文献
22.
Yury Yu. Rusakov Irina L. Rusakova Leonid B. Krivdin 《Magnetic resonance in chemistry : MRC》2014,52(5):214-221
Four‐component relativistic calculations of 77Se–13C spin–spin coupling constants have been performed in the series of selenium heterocycles and their parent open‐chain selenides. It has been found that relativistic effects play an essential role in the selenium–carbon coupling mechanism and could result in a contribution of as much as 15–25% of the total values of the one‐bond selenium–carbon spin‐spin coupling constants. In the overall contribution of the relativistic effects to the total values of 1J(Se,C), the scalar relativistic corrections (negative in sign) by far dominate over the spin‐orbit ones (positive in sign), the latter being of less than 5%, as compared to the former (ca 20%). A combination of nonrelativistic second‐order polarization propagator approach (CC2) with the four‐component relativistic density functional theory scheme is recommended as a versatile tool for the calculation of 1J(Se,C). Solvent effects in the values of 1J(Se,C) calculated within the polarizable continuum model for the solvents with different dielectric constants (ε 2.2–78.4) are next to negligible decreasing negative 1J(Se,C) in absolute value by only about 1 Hz. The use of the locally dense basis set approach applied herewith for the calculation of 77Se–13C spin‐spin coupling constants is fully justified resulting in a dramatic decrease in computational cost with only 0.1–0.2‐Hz loss of accuracy. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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To improve their properties, phenol- and carbamide-formaldehyde adhesives were modified by cellulose by-products. It has been shown that the introduction of pectol into phenol-formaldehyde resin of SFZh-3013 grade and products of sulfite-cellulose production into adhesive compositions based on carbamide-formaldehyde resins increases the plywood gluing strength and curing rate. 相似文献
25.
Sergey V. Nikitin Dmitriy A. Parkhomenko Mariya V. Edeleva Elena G. Bagryanskaya 《Journal of polymer science. Part A, Polymer chemistry》2015,53(21):2546-2556
Simulation on the kinetic scheme of enhanced spin capturing polymerizations (ESCP) were performed to reveal the influence of different parameters, e.g., initiation rate, spin capturing and side reactions on the properties (the monomer conversion, degree of polymerization, polydispersity index, and the fraction of “living” chains) of polymer obtained. The kinetic scheme of ESCP was solved numerically as well as the method of statistical moments of molecular weight distribution was applied to get some numerical expressions for analysis. The simulations showed that fast initiation rate can lead to decrease of living fraction and broadening of molecular weight distribution. Whereas high rate of spin capturing makes the polymer chains shorter but increases living character. And side reactions always decrease livingness of the polymer obtained. Finally in the case of absence of side reaction we were able to formulate criteria for formation of polymer with target molecular weight and quota of living chains via ESCP process. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2546–2556 相似文献
26.
Prof. Dr. Dmitriy M. Volochnyuk Dr. Alina O. Gorlova Prof. Dr. Oleksandr O. Grygorenko 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(62):15277-15326
This review discusses recent advances in the chemistry of saturated boronic acids, boronates, and trifluoroborates. Applications of the title compounds in the design of boron-containing drugs are surveyed, with special emphasis on α-amino boronic derivatives. A general overview of saturated boronic compounds as modern tools to construct C(sp3)−C and C(sp3)-heteroatom bonds is given, including recent developments in the Suzuki-Miyaura and Chan-Lam cross-couplings, single-electron-transfer processes including metallo- and organocatalytic photoredox reactions, and transformations of boron “ate” complexes. Finally, an attempt to summarize the current state of the art in the synthesis of saturated boronic acids, boronates, and trifluoroborates is made, with a brief mention of the “classical” methods (transmetallation of organolithium/magnesium reagents with boron species, anti-Markovnikov hydroboration of alkenes, and the modification of alkenyl boron compounds) and a special focus on recent methodologies (boronation of alkyl (pseudo)halides, derivatives of carboxylic acids, alcohols, and primary amines, boronative C−H activation, novel approaches to alkene hydroboration, and 1,2-metallate-type rearrangements). 相似文献
27.
Y. P. Rakovich M. Gerlach J. F. Donegan K. I. Rusakov A. A. Gladyshchuk 《Optics and Spectroscopy》2010,108(3):385-390
In recent years the studies of electromagnetic modes in solid spherical microcavities have been of great interest both for
their potential applications and fundamental optical properties. A system of coherently coupled microcavities may be called
a “photonic molecule” and can be employed in the tight-binding device in order to manipulate photons in micrometer length
scale. In this work we demonstrate the possibility of mode manipulation in systems of symmetric photonic molecules formed
by placing several high-Q micro-spheres in contact. We observe photonic nanojets that reflect the symmetry of the photonic
molecule, with 3 jets located at 120 degrees with respect to each other for the triangular photonic molecule. A benzene molecule-like
structure consisting of a 7-microspheres cyclic photonic molecule shows a field emission pattern similar to the spatial distribution
of the orbitals of the benzene molecule. We also present some results showing the coexistence of whispering gallery modes
and photonic nanojets in the same structure. 相似文献
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Anastasiia M. Mishura Anna S. Sklyarova Dmitriy I. Sharapa Igor’ A. Levandovsky Michael Serafin Andrey A. Fokin Vladimir N. Rodionov 《Central European Journal of Chemistry》2013,11(12):2144-2150
The rearrangement of easily accessible Cookson’s diketone with chlorosulfonic acid in chloroform followed by the acidic hydrolysis gave 6-chloro-7-hydroxy-dichloropentacyclo[6.3.0.02,6.03,10.05,9]undecane-4-one, whose syn-stereochemistry was assigned through the X-ray crystal structure analysis. This key structure was used for the stereoselective synthesis of the D 3-trishomocubane derivatives as well as for the preparation of potential drugs bearing hydroxy- and amino-functional groups. A new multigram preparative synthesis of D 3-trishomocubane was developed. 相似文献
30.
Dmitriy Alhazov Arkadiusz Gradys Pawel Sajkiewicz Arkadii Arinstein Eyal Zussman 《European Polymer Journal》2013
Analysis of the thermo-mechanical behavior of electrospun thermoplastic polyurethane (TPU) block co-polymer nanofibers (glass transition temperature ∼−50 °C) is presented. Upon heating, nanofibers began to massively contract, at ∼70 °C, whereas TPU cast films started to expand. Radial wide-angle X-ray scattering (WAXS) profiles of the nanofibers and the films showed no diffraction peaks related to crystals, whereas their amorphous halo had an asymmetric shape, which can be approximated by two components, associated with hard and soft segments. During heating, noticeable changes in the contribution of these components were only observed in nanofibers. These changes, which were accompanied with an endothermic DSC peak, coinciding with the start of the nanofibers contraction, can be attributed to relaxation of an oriented stretched amorphous phase created during electrospinning. Such structure relaxation becomes possible when a portion of the hard segment clusters, forming an effective physical network, is destroyed upon heating. 相似文献