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91.
Reaction Products of Antimony(V) Chloride and N, N′-Dimethyloxamide and their Vibrational Spectra N, N′-Dimethyloxamide reacts with antimony(V) chloride at lower temperatures to the 1:1 resp. 1:2 addition compounds I resp. II. Pyrolysis of these compounds leads to the cyclic tetrachloroantimony(V)-N, N′-dimethyloxamides (III) resp.(V). III yields with antimony(V) chloride the 1:1 adduct IV, which is transformed to V. The vibrational spectra were assigned and discussed. 相似文献
92.
Laser light is used for two-step photoionization of Na2. the first step depends on the moleculer orientation, the second step doesnot. This yields a method for the analysis of molecular alignment. 相似文献
93.
On Calcium Bromated and Iodates – Crystal Structure, X-Ray, IR and Raman Spectroscopical and Thermoanalytical Investigations The phase relationships (and both decomposition and disproportionation)of bromates and iodates of alkaline earth metals are studied by means of thermal analyses (DTA, DSC, TG) and (high-temperature) X-Ray, IR-, and (high-temperature) Raman spectroscopic measurements. The following compounds have been established: Ca(IO3)2 · 6 H2O oF 216, the isotypic Ca(BrO3)2 · H2O and Ca(IO3)2 · H2O mP 48, Ca(IO3)2 I (Lautarit) mP 36, Ca(IO3)2 II and Ca(BrO3)2. The Crystal structure of Ca(IO3)2 · H2O (brüggenite) (space group P21/c, Z = 4) has been determined by single crystal X-ray diffraction (MoKα). The final R value for 3888 reflections with Io > 3σ1 is 0.0487. The structures of bromates and iodates of alkaline earth metals known so far are discussed with respect to the energetic (mode frequencies) and geometric (bond lengths) distortion of the XO3–ions as well as the strengths of H-bonds present in the respective hydrates. 相似文献
94.
1-(5-Nitro-2-thiazolyl)-2-imidazolidinone is synthesized from 2-amino-5-nitro-thiazole and 2-chloroethyl-isocyanate. The structure of this new potent schistosomicide is established by acid and alkaline degradation as well as by synthesis starting from 2-imidazolidinone. A number of derivatives of 1-(5-nitro-2-thiazolyl)-2-imidazolidinone are reported. 相似文献
95.
Schmidt A Habeck T Merkel L Mäkinen M Vainiotalo P 《Rapid communications in mass spectrometry : RCM》2005,19(16):2211-2216
Pyrazolium-3-carboxylate and indazolium-3-carboxylate, which belong to the class of pseudo-cross-conjugated mesomeric betaines and which represent the electronically relevant partial structures of the betaine alkaloid Nigellicin, were examined by electrospray ionization mass spectrometry. These compounds decarboxylate to pyrazol-3-ylidene and indazol-3-ylidene. The formation of adducts of these new nucleophilic carbenes under the measurement conditions was examined. 相似文献
96.
The structures of the stable conformers of N-methyjpropionamide and N-methyliso-butyroamide in CCl4, solution were determined by a combination of IR spectroscopy and NMR spectroscopy with lanthanide shift reagents. N-methyl-propionamide was found to exist in the form of two rotational isomers, 1 and 2, with the ethyl group twisted out of the plane of the amide bond by the angles Ψ = 140 and 20°, respectively. For these two conformers, the enthalpy difference is ΔH = 2.13 ± 0.08 kcal mole?1 and the entropy difference ΔS = 7.81 ± 0.55 cal mole?1 grad?1. N-methylisobutyroamide exists in a single form, with the two C-methyl group positions very close to those found in the two isomers of N-methylpropionamide. 相似文献
97.
The vaterite—calcite transition above 630 K has been studied by isothermal and non-isothermal differential scanning calorimetry. Vaterite samples prepared under different conditions were investigated. The transition temperature is strongly dependent on the sample preparation. The observed transition enthalpy Htr is nearly equal for different samples and experimental conditions. From 28 measurements a value of Htr–(3.12±0.11) kJ mol–1 was obtained. The activation energy for the polymorphic transition was calculated from the Arrhenius plot and by use of isoconversional methods, as a function of the degree of conversion. The influence of the kinetic model distortion and experimental uncertainties on the obtained data was discussed. The actual value of the activation energy was assessed at Ea=(250±10) kJ mol–1 for nearly all examined samples. Functions, corresponded to the model mechanism of nuclei formation and growth, provide the unambiguous consideration of the transition kinetic for the investigated vaterite samples. Differences in the dynamic behaviour of several samples at the transition are established.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
98.
Polarography and chronopotentiometry are used to study the primary processes of the reduction of 2,2′-bipyridine at mercury electrodes in aqueous solutions (12 < pH < 14). Bipyridine and its first reduction product are strongly adsorbed. The reduction is preceded by a complex equilibrium between bipyridine and the cation of the supporting electrolyte (Li, Na, K, Ba). Due to the great excess of the cations, the equilibrium is shifted completely to the side of the complex, which exists as cis- and trans-isomer. The cis-form is more stable, forming a chelate, the trans-form however is more easily reducible. The kinetic and thermodynamic data of the isomerization are determined. The first reduction product reacts irreversibly giving a substance which can be reoxidized to bipyridine via a radical intermediate. 相似文献
99.
Attempts to prepare phosphate granates were without success. However, three arsenate granates of the type {NaCa2}[M](As3)O12 with MII ? Mg, Co, Ni have been prepared by solid state reaction and their lattice constants determined. All these arsenates are characterised by a thermal transformation into a high-temperature form, proceeding monotropically for the Mg compound, and reversibly for the Ni and Co compound. 相似文献
100.
Lukin O Müller WM Müller U Kaufmann A Schmidt C Leszczynski J Vögtle F 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(15):3507-3517
The readily available in gram quantities tris(allyloxy)knot of the amide-type 5 (knotane) can be completely and partially deprotected with nBu(3)SnH in the presence of a palladium catalyst resulting in hydroxyknotanes 7-9. These, in turn, react with diethylchlorophosphate giving rise to knotanes equipped with between one and three phosphoryl groups. Sulfonylation of bis(allyloxy)monohydroxyknotane 8 with p-toluenesulfonyl chloride and, following removal of one or two allyl groups from the intermediate monosulfonate 13, give rise to sulfonyloxy-allyloxy-hydroxy- and sulfonyloxy-dihydroxy-knotanes 15 and 14, respectively. This provides a convenient method for the preparation of knotanes with any substitution pattern. All new knotanes have been isolated in preparative amounts and as highly pure substances with an exception of allyloxy-dihydroxyknotane 9. This compound could only be obtained as a mixture with the corresponding monohydroxy-derivative 8. The structures of all synthesized compounds were established by means of FAB and MALDI TOF mass spectrometry, (1)H and (31)P NMR spectroscopy. The triphosphorylated knotane 10 exhibits high solubility in alcohols, allowing its complete enantiomeric resolution with a commercially available chiral HPLC column. (1)H,(1)H DQF-COSY correlation spectroscopy along with H/D exchange experiments and ab initio calculations provided the first detailed (1)H NMR signal assignments of knotanes in [D(6)]DMSO solution. The combination of variable temperature (1)H and (31)P NMR spectroscopy and molecular modeling has been applied to study the conformational behavior of the new knotanes in different solvents. It has been shown that in DMSO solution at room temperature knotanes exist in a relatively rigid nonsymmetrical conformation similar to that found in the solid state while faster conformational exchange leading to the average D(3) symmetrical structure was detected in a number of other solvents. 相似文献