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991.
IntroductionIthasbccndcmonstratcdthatmcthancrcformingt"ithcarbondioxidcpr0ducessynthcsisgasrichincarbonmonoxidc-x"hichisuscfulforthcs}nthcsisofaccticacid'dimcthylcthcrando.o-alcoholsll'2].Carbondioxidcref0rmingismorccndothcrmicthanstcamrcformingfCH4 CO2,'2CO 2H2Ai/'2,,=2473kJ..ol-1(l)Accordingl\"thisrcact1onnccdshighcrtcmpcraturcandlimitsspaccvclocityoffccdgas,Wehavcprct'ious1\studicdmcthancrcformingt"lthC02inthcmonotubcproccssl3J.Inordertoconvcrtmcthancinfccdgascomplctcl}',thcspaccvcloci… 相似文献
992.
993.
The molar conductances of dilute solutions of salicylic and monochloroacetic acids in binary mixtures of methanol, ethanol, 1-propanol, N,N-dimethylformamide, acetone, acetonitrile, tetrahydrofuran and dioxane with water have been measured at 25°C. The Lee-Wheaton conductance equation was fitted to the data in order to derive thermodynamic dissociation constants and limiting molar conductances. The results were compared with those in the literature pertaining to analogous media, mostly derived potentiometrically. The findings are interpreted in terms of a solvent effect on the ionization of these acids in mixed solvent systems.This paper is dedicated to the late Professor Raymond M. Fuoss on his 3rd anniversary. 相似文献
994.
Summary The interfering effect of the -radiation of radioactive isotopes of the rare earths on the non-destructive neutron activation analysis of g amounts of uranium, using the 106 KeV--line of 239Np and NaI (Tl). detector, is estimated. The errors introduced by the interfering isotope in the analysis of uranium, are determined as a function of the ratio of the concentration in the sample of the interfering element and uranium. In addition, the possibilities of determining the quantitative effect of these elements are described. The use of the proposed method is demonstrated by the analysis of some geological samples.
Zerstörungsfreie Neutronenaktivierungsanalyse von Uran über die 106 KeV--Strahlung von Neptunium-239II. Einfluß der Seltenen Erden
Zusammenfassung Es wird die Störung bestimmt, die die -Strahlung der radioaktiven Isotope Seltener Erden bei der zerstörungsfreien Neutronenaktivierungsanalyse von Mikrogramm-Mengen Uran über die 106 KeV--Linie des 239Np mit Hilfe eines NaJ(Tl)-Detektors hervorrufen kann. Die Fehler in der Analyse von Uran, die das Störisotop verursachen kann, werden als Funktion des Verhältnisses der Konzentration des Störelements zu der des Urans in der Probe bestimmt. Es werden Möglichkeiten beschrieben, den Einfluß störender Elemente quantitativ zu erfassen. Die Brauchbarkeit der vorgeschlagenen Methode wurde durch Analyse einiger geologischer Objekte bewiesen.
Part I: Z. Anal. Chem. 257, 23 (1971). 相似文献
995.
Recent data on classical and modified methods for the synthesis of quinoline systems by the Skraup and Doebner-Miller reactions,
not included in reviews on heterocycles, are discussed.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 803–824, June, 2006. 相似文献
996.
A global optimization strategy, based upon application of a genetic algorithm (GA), is demonstrated as an approach for determining the structures of molecules possessing significant conformational flexibility directly from gas-phase electron diffraction data. In contrast to the common approach to molecular structure determination, based on trial-and-error assessment of structures available from quantum chemical calculations, the GA approach described here does not require expensive quantum mechanical calculations or manual searching of the potential energy surface of the sample molecule, relying instead upon simple comparison between the experimental and calculated diffraction pattern derived from a proposed trial molecular structure. Structures as complex as all-trans retinal and p-coumaric acid, both important chromophores in photosensing processes, may be determined by this approach. In the examples presented here, we find that the GA approach can determine the correct conformation of a flexible molecule described by 11 independent torsion angles. We also demonstrate applications to samples comprising a mixture of two distinct molecular conformations. With these results we conclude that applications of this approach are very promising in elucidating the structures of large molecules directly from electron diffraction data. 相似文献
997.
Absolute rate constants are reported for the addition of the 1‐[(tert‐butoxy)carbonyl]ethyl (= 2‐(1,1‐dimethylethoxy)‐1‐methyl‐2‐oxoethyl) radical .CHMeCO2(t‐Bu) to several cyclic and monosubstituted alkenes in MeCN as obtained by time‐resolved electron paramagnetic resonance (EPR). The activation energies for the addition of this alkyl radical are mainly governed by the addition enthalpy but are also substantially lowered by the ambiphilic effect and by relief of cyclic strain. 相似文献
998.
Bile acid-based acyclic receptors bearing two imidazole and benzimidazole moieties have been synthesized. Anion binding studies using 1H NMR revealed that imidazolium receptor exhibits high selectivity for chloride ion while benzimidazolium receptor showed selectivity for Y-shaped acetate ion through hydrogen bond interactions involving imidazolium C-2 and acetyl methylene hydrogens. 相似文献
999.
Thermal decomposition of bis(hexamethylbenzene)iron(0) in the presence of carbon monoxide yields a novel carbonyl iron complex, [C6(CH3)6]Fe(CO)2. The cyclohexadiene complex [C6(CH3)6]Fe(C6H8) is obtained from reaction of bis(hexamethylbenzene)iron(0) with either 1,3-cyclohexadiene or benzene, and the yield is much greater in the presence of hydrogen gas. Interaction of bis-(hexamethylbenzene)iron(0) with 2-butyne induces a catalytic cyclotrimerization to give more hexamethylbenzene. Kinetic and isotope distribution studies indicate that the primary step in these reactions is not a direct loss of one ring ligand, but rather an insertion of the iron center into one of the ligand methyl CH bonds, leading to a benzyl hydride complex species. Mechanisms for the subsequent reactions of this iron hydride species are proposed. 相似文献
1000.
A novel and green approach for efficient and rapid synthesis of polyhydroquinoline derivatives via unsymmetric Hantzsch reaction using organocatalysts at room temperature was reported. The process is a simple, environmentally friendly, rapid, and high yielding reaction for the synthesis of polyhydroquinoline derivatives. The catalytic efficiency of various small organocatalysts such as l-proline, trans-4-hydroxy-l-proline, l-thiaproline, dl-phenylglycine, and (−)-cinchonidine was studied under aqueous, organic, and solvent free conditions. 相似文献