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211.
Lilian F. J. Noël Ian A. Maxwell Willy J. M. Van Well Anton L. German 《Journal of polymer science. Part A, Polymer chemistry》1994,32(11):2161-2168
Recently a model has been developed capable of predicting absolute monomer concentrations and their ratios in the polymer, aqueous, and monomer droplet phases as a function of conversion in batch emulsion copolymerizations without using any adjustable parameters. In this article the sensitivity of model predictions of composition drift toward deviations of 10% in all model parameters (maximum swellabilities of monomer in the polymer phase, water solubilities, reactivity ratios, and monomer and polymer densities) was estimated using the monomer combination methyl methacrylate-styrene as an example. From the sensitivity analysis it can be concluded that the reactivity ratios are the most important parameters affecting composition drift. The effects of deviations in maximum swellabilities and monomer and polymer densities on composition drift can be neglected, while the water solubility is important only in those cases where the amount of monomer in the aqueous phase cannot be neglected as compared with the total monomer amount. © 1994 John Wiley & Sons, Inc. 相似文献
212.
Mickaël Pauvert Sylvain C. Collet André Y. Guingant Michel Evain 《Tetrahedron letters》2005,46(17):2983-2987
Addition of cyanide ion to chiral N-acyl-quinolinium and N-acyl-isoquinolinium salts led selectively to 1,2-addition products. Removal of the chiral auxiliary affords the title compounds in pure enantiomeric form. 相似文献
213.
György Bor Urs K. Dietler Piero Pino Anthony Poë 《Journal of organometallic chemistry》1978,154(3):301-315
The kinetics of the reaction of tetracobalt dodecacarbonyl with carbon monoxide to form dicobalt octacarbonyl in n-hexane have been investigated over a wide range of temperature and CO pressure. The reaction is first order in [Co4(CO)12]; the order in [CO] changes between one (at low pressures and high temperatures) and two (at high pressures and low temperatures).Activation parameters have been estimated and a mechanism involving initial reversible breaking of one CoCo bond, followed by irreversible breaking of a second, is proposed. The first step involves concerted addition of CO while the second can proceed with or without such addition. 相似文献
214.
Zusammenfassung 1,3-Dimethyl-4,5-diaminouracil (DAL) hat sich als sehr empfindliches Reagens zum selektiven Nachweis von Co2+-Ionen im stark alkalischen Medium einer Phosphatpufferlösung (pH=11,20) erwiesen. Es wurden vier Additionsverbindungen von DAL mit den Zentralatomen Cd(II), Pd(II), Ni(II) und Co(II) im Verhältnis Me DAL=1 2 hergestellt. Spektrophotometrische Untersuchungen weisen darauf hin, daß bei pH 6 bis 7 eine Komplexverbindung im Verhältnis CoDAL=12 gebildet wird.
Summary 1,3-dimethyl-4,5-diaminouracil (DAL) has been found to be a very sensitive reagent for the selective detection of Co2+ ions in strong alkaline medium of a phosphate buffer solution (pH=11.20). Four addition compounds of DAL with the central atoms Cd(II), Pd(II), Ni(II) and Co(II) with the ratio MeDal=12 have been prepared. Spectrophotometric studies indicate that at pH=6–7, complex compound is produced with the ratio CoDAL=12.相似文献
215.
Cyclocondensation of 1-aryl-3-ferrocenyl-2-propen-1-ones (1) with hetaryl hydrazines resulted in N-hetaryl-3-aryl-5-ferrocenyl pyrazolines (3, 4). The analogous 3-aryl-1-ferrocenyl-2-propen-1-ones (5) gave the isomeric N-hetaryl-5-aryl-3-ferrocenyl-pyrazolines (6, 10), but in lower yield. The reaction of aryl-chalcones (7) with 4-hydrazino-phthalazinone led to 3,5-bis-aryl-N-hetaryl-pyrazolines (8) or to the corresponding ene-hydrazones (9). The structure of the new compounds was established by IR, 1H and 13C NMR spectroscopy, including DNOE, HMQC, HMBC and DEPT methods. For compounds 1b, 3b and 8b the stereo structure was elucidated also by X-ray diffraction. 相似文献
216.
al-Khalili A Thomas R Ehlerding A Hellberg F Geppert WD Zhaunerchyk V af Ugglas M Larsson M Uggerud E Vedde J Adlhart C Semaniak J Kamińska M Zubarev RA Kjeldsen F Andersson PU Osterdahl F Bednarska VA Paál A 《The Journal of chemical physics》2004,121(12):5700-5708
Dimethyl disulfide (DMDS) and N-methylacetamide are two first choice model systems that represent the disulfide bridge bonding and the peptide bonding in proteins. These molecules are therefore suitable for investigation of the mechanisms involved when proteins fragment under electron capture dissociation (ECD). The dissociative recombination cross sections for both protonated DMDS and protonated N-methylacetamide were determined at electron energies ranging from 0.001 to 0.3 eV. Also, the branching ratios at 0 eV center-of-mass collision energy were determined. The present results give support for the indirect mechanism of ECD, where free hydrogen atoms produced in the initial fragmentation step induce further decomposition. We suggest that both indirect and direct dissociations play a role in ECD. 相似文献
217.
Patrick Gredin Gwenaël Corbel Jonathan P. Wright Nathalie Dupont Ariel de Kozak 《无机化学与普通化学杂志》2003,629(11):1960-1964
Ba3Cu2Al2F16 is monoclinic: a = 7.334(1)Å, b = 5.320(2)Å, c = 16.022(1)Å, β = 96.34(1)°, Z = 2. Its crystal structure was solved in the space group P21 (No. 4) from synchrotron X‐ray single crystal data using 2685 unique reflections (2639 with Fo/σ(Fo) > 4). The final R factor is 0.044. The structure consists of a succession along the c‐axis of the cell of three layers of two different kinds of sheets developing in the (a, b) plane. The first one, formulated [(AlF5)2]∞4— and hereafter named A, is built up from infinite cis‐chains of aluminium‐fluorine octahedra [AlF6], linked by two vertices and distanced by a. The second one, formulated [Cu2AlF11]∞4— and named B, is bidimensional. It is constituted of distorted copper‐fluorine octahedra [CuF6], linked by edges, which form infinite chains interconnected by three vertices of isolated [AlF6] octahedra. The stacking sequence of the sheets is (A, B, B)∞. The barium ions, 12‐coordinated, are inserted between the sheets. The crystal structure of Ba3Cu2Al2F16 is closely related to that of Ba4Cu2Al3F21. Only the proportion and the stacking sequence of the two kinds of sheets in the c‐direction differ, according to two different compositions and two different symmetries. 相似文献
218.
N. V. Gérbéléu K. M. Indrichan V. B. Arion 《Theoretical and Experimental Chemistry》1991,27(2):187-192
The mass spectra of the coordination compounds of nickel(II) with the bis-S-substituted thiosemicarbazones of 2,4-pentanedione (R2H2L) with the general formula [NiR2HL]X and of 3-oxo-2,4-pentanedione (H2R2LO) with the general formula NiR2LO were studied. A distinguishing feature of the mass spectra of [NiR2HL]X is the absence of molecular ion peaks. The initial point of fragmentation is the [M - HX] ions. The strongest lines in spectra of NiR2LO are those due to the elimination of R and R-H. At the first stage the fragmentation of all the investigated compounds takes place mainly through only one of the thiosemicarbazide residues. At the second stage the 2,4-pentanedione (3-oxo-2,4-pentanedione) residue is eliminated, after which the remaining thiosemicarbazide part dissociates. A significant part of the fragmentation paths was confirmed by the peaks of the metastable ions and also by the mass spectra of the deuterated analogs.Institute of Chemistry, Academy of Sciences of the Moldavian SSR, Kishinev. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 2, 205–211, March–April, 1991. Original article submitted August 19, 1986. 相似文献
219.
220.