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11.
Alain Deffieux Maurice Sepulchre Nicolas Spassky 《Journal of organometallic chemistry》1974,80(3):311-327
The reaction between organozinc or organocadmium derivatives and different chiral hydroxy compounds leads to the corresponding alcoholates and glycolates which can be used as initiators in polymerizations.The composition of such initiators is defined by the ratio iS = R-M-O/O-M-O of the number of alkylalkoxy groups to the number of dialkoxy groups. This ratio depends on the nature of the organometallic and hydroxy compound and on the conditions of reaction used to prepare them.Toward a given hydroxy compound, the reactivity of the organometallic derivatives follows the order: ZnEt2 > CdEt2 > CdMe2.Primary alcohols and 1,2-diols are more reactive than secondary alcohols in the case of organozinc compounds, while in the case of organocadmium compounds the secondary alcohols are more reactive than primary alcohols, but less reactive than 1,2-diols. The kinetics of the reaction can be followed by monitoring the variation of optical activity of the solution.Several compounds having definite stoichiometry have been isolated and identified by their NMR spectra. 相似文献
12.
Philippe Dumas Nicolas Spassky Pierre Sigwalt 《Journal of polymer science. Part A, Polymer chemistry》1974,12(5):1001-1010
The polymerization in bulk of racemic tert-butyl thiirane with a chiral initiator resulting from the reaction between diethylzinc and (? )3,3-dimethyl-1,2-butanediol produces an optically active polymer by preferential consumption of R enantiomer. The unreacted monomer is enriched in S enantiomer. The relative rate r of consumption of R enantiomer versus S enantiomer is as high as 2.8. Obtained polymer could be separated into two crystalline fractions: an optically active fraction, formed from regular sequences of R type enantiomeric units, and an optically inactive fraction which corresponds to a racemate. Experimental results are consistent with a stereospecific mechanism of addition, the two enantiomers being chosen by two different type of sites. The stereoelective process is due to an unequal number of these two types of sites. 相似文献
13.
V.V. Mikhailin D.A. Spassky V.N. Kolobanov A.A. Meotishvili D.G. Permenov B.I. Zadneprovski 《Radiation measurements》2010,45(3-6):307-310
Lutetium borates and phosphates doped with RE3+ ions are perspective scintillators. In the paper, the results of the luminescence spectroscopy of LuPO4 and LuBO3 doped with Pr3+, Ce3+, Tb3+ and Eu3+ under synchrotron radiation excitation are presented. The processes of the energy transfer from the host lattice to the luminescence centers are considered. The creation of excitons at the edge of fundamental absorption region is shown. The bandgap values for lutetium borate and phosphate were estimated. 相似文献
14.
Daniel Grenier Robert E. Prud'Homme Alain Leborgne Nicolas Spassky 《Journal of polymer science. Part A, Polymer chemistry》1981,19(7):1781-1793
S(?) and R(+) enantiomers of α-methyl-α-ethyl-β-propiolactone (MEEPL) were prepared in an eight-step synthesis with respective optical purities of 99 and 97% determined by 1H-NMR (250 MHz) spectroscopy. Polymers (PMEPL) of different enatiomeric compositions were prepared with an anionic-type initiator. Substantial differences in physical properties were observed between the racemic and optically pure polymers; for example, the melting point of the latter is 42°C higher than that of the former. Chiroptical properties of PMEPLs are reported. The 13C-NMR (100.62 MHz) spectra of the polymers indicated that the distribution of configurational units in the macromolecular chain is random. 相似文献
15.
Nicolas Spassky 《Macromolecular Symposia》1992,53(1):367-378
Different synthetic methods for the preparation of polymers by ring-opening polymerization with various distribution of enantiomeric units in the macromolecular chain are available. The structure of prepared polymers is determined by 1H and 13C NMR, X-rays diffraction, ORD and CD. Physicochemical and mechanical properties may strongly depend upon the enantiomeric composition of the polymer chain. In several cases racemate mixtures of polyenantiomers form stereocomplexes with enhanced thermal properties. 相似文献
16.
17.
Correlation features of the reaction 9Be(d, pγ)10Be at Ed=15.3 MeV and structure of the 10Be nucleus
N. S. Zelenskaya A. V. Ignatenko V. M. Lebedev N. V. Orlova A. V. Spassky 《Physics of Atomic Nuclei》2001,64(11):1909-1916
Double-differential cross sections for the reaction 9Be(d, pγ)10Be at E d=15.3 MeV are measured for proton emission into the forward hemisphere. All even spin-tensor components of the density matrix for the 2+ 3.37-MeV state of the residual nucleus are reconstructed in a model-independent way. The angular distributions of the populations of the magnetic substates and of the tensors of the angular-momentum orientation for the state in question are also obtained. The experimental results are compared with the results of the calculations performed by the coupled-channel method under the assumption of the neutron-stripping mechanism. The calculated correlation features are found to be highly sensitive to the wave functions for the participant nuclei, especially the 10Be nucleus. The importance of taking into account multistep processes in the reaction being considered is demonstrated. 相似文献
18.
E. S. Konobeevski V. I. Kukulin S. V. Zuyev V. M. Lebedev M. V. Mordovskoy A. V. Spassky 《Bulletin of the Russian Academy of Sciences: Physics》2014,78(5):341-344
The great disagreement between theory and experiment observed in nd and pd interactions indicates that investigations of mechanisms for various processes in few-nucleon systems should be continued. It is planned to investigate the reactions d + 3H → 3He + (nn) and 3He + d → 3H + (pp) in order to study nn and pp correlations in 3He and 3H nuclei. Test measurements of the d + 2H → 2He + (nn) reaction, performed with the deuteron beam at the Institute of Nuclear Physics, confirm that it is methodologically possible to perform the planned experiments. 相似文献
19.
N. R. Krutyak D. A. Spassky I. A. Tupitsyna A. M. Dubovik 《Optics and Spectroscopy》2016,120(1):45-49
Based on real structure and optical properties of the dermis, we analyzed the possibility of polarimetric measurement of glucose content in the skin. It was shown that, at physiological concentrations of glucose in the interstitial fluid, the optical activity of glucose is not manifested in the polarization and optical properties of the tissue, since the optical activity of glucose is almost completely suppressed by the linear birefringence of the dermis. 相似文献
20.
Maurice Sepulchre Nicolas Spassky Daniel Van Ooteghem Eric J. Goethals 《Journal of polymer science. Part A, Polymer chemistry》1974,12(8):1683-1693
An 1H 300-MHz NMR spectroscopic study of deuterated poly(propylene sulfide) shows that methylene protons are sensitive to triad effects. It was possible to distinguish i, hi, s, and hs triads. Experimental values found for different polymers are in good agreement with theoretical amounts obtained from statistical probability calculation. The methyl groups are also slightly stereosensitive. By using optically active deuterated monomers with different R/S ratios it was possible to confirm the assignment of peaks and the tacticity. Nondeuterated polymers give very complicated spectra, and only the highly stereoregular polymer could be analyzed through its ABCX3 spin system. 相似文献