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991.
The (15)N-labeled diammine(mu-oxo)ruthenium complex cis,cis-[(bpy)(2)(H(3)(15)N)Ru(III)ORu(III)((15)NH(3))(bpy)(2)](4+) ((2-(15)N)(4+)) was synthesized from cis,cis-[(bpy)(2)(H(2)O)Ru(III)ORu(III)(H(2)O)(bpy)(2)](4+) by using ((15)NH(4))(2)SO(4) and isolated as its perchlorate salt in 17% yield. A 1:1 mixture of (2-(15)N)(4+) and nonlabeled cis,cis-[(bpy)(2)(H(3)(14)N)Ru(III)ORu(III)((14)NH(3))(bpy)(2)](4+) were electrochemically oxidized in aqueous solution. The gaseous products (14)N(2) and (15)N(2) were formed in equimolar amounts with only a small amount of (14)N(15)N detected. This demonstrates that dinitrogen formation by oxidation of the diammine complex proceeds by intramolecular N---N coupling. 相似文献
992.
Osipov SN Golubev AS Sewald N Michel T Kolomiets AF Fokin AV Burger K 《The Journal of organic chemistry》1996,61(21):7521-7528
A new method for the preparation of alpha-chlorodifluoromethyl-, alpha-bromodifluoromethyl-, and alpha-difluoromethyl-substituted alpha-hydroxy and alpha-amino acid esters 11, 19-21 is described. The key step of the synthesis is the regioselective alkylation of ketones 5, 7-9 and imines 16-18 with C-nucleophiles. The ketones 7-9 are readily available from 3,3,3-trifluorolactate 1 by a five-step procedure. Subsequent removal of the protecting groups from 19-21 provides the corresponding free amino acids 25, 26, 28. 相似文献
993.
Florian Blaser Pierre-Franois Deschenaux Thomas Kallimopoulos Andr Jacot-Guillarmod 《Helvetica chimica acta》1991,74(4):787-790
Synthesis of (?)-(6R)- and (+)-(6S)-Tetrahydro-6-[(Z)-pent-2-enyl]-2H-Pyran-2-one, lactones from Jasminum grandiflorum L. and from Polianthes tuberosa L. (?)-(2S)-Ethyl 2-hydroxyhexanedioate ((2S)- 2 ) was obtained by kinetic resolution of racemic ethyl 2-hydroxy-hexanedioate with baker's yeast. The key intermediates (+)-(5R)- and (?)-(5S)-ethyl 5,6-epoxyhexanoate ((5R)- and (5S)- 6 , resp.) are proved to be useful synthons for the total synthesis of chiral 6-alkyl-δ-lactones, as exemplified by the preparation of both enantiomers of jasmine lactone ((6R)- and (6S)- 10 , resp.). 相似文献
994.
The complexes [Fe(tdci)2]Cl3 and [Al(tdci)2]Cl3 (tdci = 1,3,5-trideoxy-1,3,5-tris(dimethylamino)-cis-inositol) were prepared and characterized by mass spectrometry, NMR spectroscopy, and magnetic-susceptibility measurements. The formation constants were determined in aqueous solution (25°, 0.1M KCl) by potentiometric titration. pK values of H3(tdci)3+: 5.89, 7.62, 9.68; FeIII complexes: log βML = 18.8, log β = 32.6; AlIII complexes: log βML = 14.3, logβ = 26.4. The protonated complex [FeH(tdci)2]4+ has also been identified. In contrast to the high stability of the FeIII and AlIII complexes, only weak interactions of tdci with CuII have been observed in aqueous solution (25°, 0.1M KNO3). 相似文献
995.
Prof. Dr. H. G. Kilian 《Colloid and polymer science》1977,255(8):740-754
Summary A thermodynamic treatment of homo-polymer systems out of linear chains with folded chain crystals is developed outgoing from appropriate models for single component systems. An expansion of thermodynamics to multi-micro-phase systems the structure of which is partially or totaly frozen is indispensable. General properties of melt crystallized homopolymers with folded chain crystals can be recognized indeed when the thermodynamic formalisms developed are applied.
Notation g c (y);g m (Y) molar Gibbs-free energy of a chain of a lengthy within an extended chain crystal and the melt rsp - g o c ;g o m molar free enthalpy of the unit in the crystal lattice and the melt rsp - g(y,y, f) molar Gibbs-function of an ideally folded chain crystal with the fold heighty f - gco(y, y ef,y f) molar free enthalpy of the crystal corey co - g 0 ex ((yef) excess free enthalpy of the longitudinal layers of folded chain crystals - g f(yef,g o ex ) molar free enthalpy of the longitudinal layers of the folded chain crystals - g tot molar free enthalpy of a chain of the lengthy within a folded chain crystal with longitudinal layers - h o 1c ,h o m molar enthalpy of the chain unit within the crystal lattice and the melt rsp - h =h o m -h o c molar heat of fusion of the unit - C p=C p m -C p c difference of the molar specific heat of a unit within the melt and within the chain crystal - h D molar defect enthalpy of local defects within the crystal lattice - h D molar defect enthalpy of the unit - s o c ,s o m molar entropy of the chain unit within the crystal lattice and the melt rsp - s c m conformational entropy of a chain in the melt - s gk conformational entropy of a chain of lengthy within a super-lattice as indicated in figure 5, - s molar entropy of fusion of the melt - s n c nematic configurational entropy - T absolute temperature - T M melting temperature of extended chain crystals of infinite size - T M(y) melting temperature of extended chain crystals containing only chains of the lengthy - T M (y, y f) melting temperatureof folded chain crystals of the thicknessy f composed of chains of the lengthy - T M(y f) melting temperature of folded chain crystals of the thicknessy fy - eh excess free enthalpy of the chain ends occupying crystallographic places - ef excess free enthalpy of a single fold loop - z coordination number of the lattice - 7 Euler's constant - R Boltzmann's constant - y number of chain units - y f height of lamelliform folded chain crystals - f=(y/y f - 1) number of fold loops of a chain of a lengthy when being built into a folded chain crystal of the thicknessy f - y co thickness of the crystal core of the simplified twophase model - y et average thickness of the surface layers of folded chain crystals - N c number of crystallized units of a chain of the lengthy - x c molar number of crystallized units of a chain of the lengthy - x nc molar number of noncrystallized units - excess free enthalpy parameter - (y f) thickness distribution of the fold heightsy f With 15 figures and 2 tables 相似文献
Zusammenfassung Das Schmelzen in polymeren Einteilchensystemen mit Faltungskristallen einheitlicher Dicke kann thermodynamisch als Umwandlung 1. Ordnung in einer Richtung behandelt werden, wenn die Faltungslänge bis zur Umwandlungstemperatur konstant bleibt (Faltungslänge als innerer Zusatzparameter). Eine wesentliche begriffliche Erweiterung ist für eine phänomenologische Beschreibung mit den Mitteln der Thermodynamik unumgänglich, wenn eine Faltungskristallit-Dickenverteilung existiert, weil dann prinzipiell nur noch partielle Koexistenz bestimmter Fraktionen metastabiler autonomer Mikrophasen mit der Schmelze möglich ist. Partielles Aufschmelzen und Rektistallisation können so dann auch in Betracht genommen werden. Die entwickelten Konzeptionen bewähren sich in der Anwendung auf bekannte Experimente.
Notation g c (y);g m (Y) molar Gibbs-free energy of a chain of a lengthy within an extended chain crystal and the melt rsp - g o c ;g o m molar free enthalpy of the unit in the crystal lattice and the melt rsp - g(y,y, f) molar Gibbs-function of an ideally folded chain crystal with the fold heighty f - gco(y, y ef,y f) molar free enthalpy of the crystal corey co - g 0 ex ((yef) excess free enthalpy of the longitudinal layers of folded chain crystals - g f(yef,g o ex ) molar free enthalpy of the longitudinal layers of the folded chain crystals - g tot molar free enthalpy of a chain of the lengthy within a folded chain crystal with longitudinal layers - h o 1c ,h o m molar enthalpy of the chain unit within the crystal lattice and the melt rsp - h =h o m -h o c molar heat of fusion of the unit - C p=C p m -C p c difference of the molar specific heat of a unit within the melt and within the chain crystal - h D molar defect enthalpy of local defects within the crystal lattice - h D molar defect enthalpy of the unit - s o c ,s o m molar entropy of the chain unit within the crystal lattice and the melt rsp - s c m conformational entropy of a chain in the melt - s gk conformational entropy of a chain of lengthy within a super-lattice as indicated in figure 5, - s molar entropy of fusion of the melt - s n c nematic configurational entropy - T absolute temperature - T M melting temperature of extended chain crystals of infinite size - T M(y) melting temperature of extended chain crystals containing only chains of the lengthy - T M (y, y f) melting temperatureof folded chain crystals of the thicknessy f composed of chains of the lengthy - T M(y f) melting temperature of folded chain crystals of the thicknessy fy - eh excess free enthalpy of the chain ends occupying crystallographic places - ef excess free enthalpy of a single fold loop - z coordination number of the lattice - 7 Euler's constant - R Boltzmann's constant - y number of chain units - y f height of lamelliform folded chain crystals - f=(y/y f - 1) number of fold loops of a chain of a lengthy when being built into a folded chain crystal of the thicknessy f - y co thickness of the crystal core of the simplified twophase model - y et average thickness of the surface layers of folded chain crystals - N c number of crystallized units of a chain of the lengthy - x c molar number of crystallized units of a chain of the lengthy - x nc molar number of noncrystallized units - excess free enthalpy parameter - (y f) thickness distribution of the fold heightsy f With 15 figures and 2 tables 相似文献
996.
Thomas P. Coohill Sharon P. Moore Stephanie Drake 《Photochemistry and photobiology》1977,26(4):387-391
Abstract. The ability of UV-irradiated African green monkey kidney cells (CV-1) to support the growth of unirradiated herpes simplex virus type 1 as measured by plaque forming ability has been investigated. The lowering of plaque formation by the virus when the host cell was irradiated was examined at thirteen different wavelengths. An action spectrum for this cellular parameter (capacity) was obtained in the wavelength region of 235–302 nm. This action spectrum points to nucleic acid as the critical target molecule for this effect. 相似文献
997.
Prof. Dr. G. Zigeuner W. Galatik W. -B. Lintschinger F. Wede 《Monatshefte für Chemie / Chemical Monthly》1975,106(5):1219-1233
The title compounds7 are formed in a general reaction by heating β-isothiocyanoketones3 with primary amines in inert solvents, or by thermal elimination of water from tetrahydro-6-hydroxy-6-methyl-2(1H)-pyrimidinethiones5, also in inert solvents. The 1-alkyl compounds can also be prepared under similar conditions from α,β-unsaturated ketones by reaction with alkylammonium rhodanides. The NMR-spectra show that the 1-substituted dihydro-6-methyl-2(1H)-pyrimidinethiones are in tautomeric equilibrium with the tetrahydro-6-methylene-2(1H)-pyrimidinethiones13. The reactivity of 1-alkyl and 1-aryldihydro-6-methyl-2(1H)-pyrimidinethiones is similar to that of dihydro-4,4,6-trimethyl-2(1H)-pyrimidinethione7 j, although their ring stability is certainly less. 相似文献
998.
Benedict D. Fabian Thomas P. Fehlner Ling-Shine J. Hwang Jay A. Labinger 《Journal of organometallic chemistry》1980,191(2):409-413
The He(I) photoelectron spectra of (η5-C5H5)Fe(CO)2R, where R = CH3, η1-C3H5 and η1-C5H5, have been recorded. The lowest lying ion states result from ionization of molecular orbitals with large Fe 3d character; these move to lower anergy when R places double bonds in an allylic relationship to the metal atom. The cyclic voltammetric oxidation potential correlates well with the energies of the lowest ion states. A significant interaction between olefin π orbitals and the allylic metal center is proposed. 相似文献
999.
Prof. Dr. E. Nachbaur A. Popitsch P. Burkert 《Monatshefte für Chemie / Chemical Monthly》1974,105(4):822-833
According to spectroscopic (IR, broadline proton NMR) and chemical (alkylation) investigations of disilver sulphamide the following molecular structure is assumed: $$\begin{gathered} O \hfill \\ || \hfill \\ H_2 N\_\_S\_\_NAg| \hfill \\ OAg \hfill \\ \end{gathered}$$ From the IR and NMR data deduction concerning the nature of the chemical bonds in this compound is possible. The instability of the still unknown mono-and trisilver sulphamide is discussed with regard to the structure of disilver sulphamide. 相似文献
1000.
Temperature and enantioseparation by macrocyclic glycopeptide chiral stationary phases 总被引:1,自引:0,他引:1
Seventy-one chiral compounds were separated on four macrocyclic glycopeptide chiral selectors: teicoplanin, its aglycone, ristocetin A and vancomycin, using three possible separation modes: reversed phase with methanol/buffer mobile phases, normal phase with hexane/ethanol mobile phases and polar ionic mode (PIM) with 100% methanol mobile phase with trace amounts of acid and/or base. These 148 separations were studied in a 5-45 degrees C temperature range. Peak efficiencies always increased with temperature, but in only 17% of the separations studied a small increase of the enantioresolution factor was observed. In the majority (83%) of the cases, the enantioresolution decreased or even vanished when temperature increased. All 148 Van't Hoff plots were linear showing that the selector did not change in the temperature range studied. The calculated enthalpy and entropy variations showed that the interaction of the solute with the stationary phase was always enthalpy driven with normal and reversed mobile phases. It could be enthalpy as well as entropy driven with PIM mobile phases strongly dependent on the solute. The plots of delta(deltaH) versus delta(deltaS) were linear in most cases (enthalpy entropy compensation). This observation cannot be used to give clear information on chiral recognition mechanisms, but it allowed identifying specific stationary phase-solute interactions because the points corresponding to the respective thermodynamic parameters were clearly delineated from the general compensation lines. 相似文献