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71.
Zusammenfassung Es werden einstufige Synthesen desGlomerins (2) [1,2-Dimethyl-4(1H)-chinazolinon] und desArborins (3) [1-Methyl-2-benzyl-4(1H)-chinazolinon] bekanntgegeben.
Syntheses of heterocycles, CXXX: Glomerine and arborine
A one step synthesis ofglomerine (2) [1.2-dimethyl-4(1H)-quinazolinone] andarborine (3) [1-methyl-2-benzyl-4(1H)-quinazolinone] is described.相似文献
72.
The oxidation of aldehydes by dicyclohexyl-18-crown-6-potassium permangante complex is presented. Results obtained by this procedure showed that the presence of crown ether (DCC) and the catalyst play an important role in the oxidation of the aldehydes. The stoichiometry found corresponds to 2 μeq of permanganate per 1 μmol of aldehydes in all cases. Alcohols and ketones are not oxidized. Finally, a method for quantitative evaluation of aldehydes is proposed. 相似文献
73.
The ion product of water and the dissociation constants of carbonic acid have been determined in 0.1, 1.0, 3.0, and 5.0M NaClO4 at 25°C. The ion product of water K
w
'
has been evaluated by emf measurements with a combined glass electrode in NaClO4 solutions containing 0.001–0.1M HCLO4 or NaOH. The product K
H
'
K
l
'
K
2
'
of the Henry constant for CO2 and the dissociation constants for H2CO3 have been determined by titration of carbonate solutions equilibrated with pCO2 =10–3.52 atm, and K
2
'
has been evaluated by potentiometric titration and by measuring the H+ concentration at fixed HCO
3
–
and CO
3
2-
concentrations. The ion interaction (Pitzer) equations are applied to describe the constants K
w
'
, K
2
'
and K
H
'
H
1
'
K
2
'
as a function of the NaClO4 concentration. The experimental data are used to evaluate the mixing parameters
i/ClO
4 and
i/ClO
4
-/Na+ fori = OH
-,HCO
3
-
andCO
3
2- 相似文献
74.
Zusammenfassung Die Abhängigkeit der Struktur des o-Hydroxymandelsäurelactons von Lösungsmittel und Temperatur wird mit Hilfe IR- und NMR-spektroskopischer Methoden nachgewiesen.
The temperature and solvent dependence of the structures of 2-hydroxymandelic acid lactone and dioxindole have been shown by IR and NMR spectroscopy.相似文献
75.
Metal Complexes with Anionic Ligands of Elements of the Main Group IV. VIII Pentacarbonyltrihalogenostannidometalate(O) Complexes of Chromium, Molybdenum, and Tungsten with Fluorine and Iodine Containing Trihalogenostannido Ligands In methylenechloride [As(C6H5)4][SnF3] readily reacts with the metalhexacarbonyls forming the arsoniumsalts of the pentacarbonyltrifluorostannidometalate(O) complexes, [M(CO)5SnF3]? (M ? Cr, Mo, W). Exclusively by the reaction of the intermediately formed complex Cr(CO)5THF only one pure triiodostannidometalate(O) Complex, [N(C2H5)4][Cr(CO)5SnJ3], could be isolated. The trihalogenostannidometalate(O) complexes [M(CO)5SnClX2]? (X ? F: M ? Cr, Mo, W; X ? J: M ? Cr) could be prepared by SnX2-insertion reactions of the [M(CO)5Cl]? complexes. The bonding properties of the halogenostannide ions are discussed on the bases of the IR spectra of their metalate(O) complexes. 相似文献
76.
The protonation and deprotonation rates of the coordinated amide group in the Cu2+ complexes with Nα-(2-pyridyl-methyl)-glycinamide (I) and Nα-(2-pyridyl-methyl)-glycineethylamide (II) have been studied by stopped flow techniques. It is shown that the rate determining step of the formation of the complex with the deprotonated amide group is given by the rate of water dissociation from Cu2+. Weaker bases than OH? or stronger acids than water can react by a different path, in which the proton transfer and/or the rotation from the O-co-ordinated into the N-co-ordinated form and vice versa is rate determining. 相似文献
77.
Lee D Pervushin K Bischof D Braun M Thöny-Meyer L 《Journal of the American Chemical Society》2005,127(11):3716-3717
The heme chaperone CcmE is essential for the delivery of heme to c-type cytochromes. It forms an unusual transient, yet covalent, bond between an essential histidine, H130, and heme. We report on the discovery of the chemical structure of this bond solved by NMR, where the heme vinyl is cross-linked at the beta carbon to the Ndelta1 of H130. As this type of heme linkage has not been described previously in any cytochrome or hemoprotein, it represents a novel type of heme-histidine complex. 相似文献
78.
G. J. De Jong U. A. Th. Brinkman 《Journal of Radioanalytical and Nuclear Chemistry》1977,35(1):223-232
For the system liquid anion-exchanger—Cr(III)−NCS−, an investigation has been made of the dependence of the percentage extraction of Cr(III) on parameters such as standing
time of the Cr(III)−NCS− solution, temperature, pH and type of exchanger. Quantitative extraction of e.g. 4·10−4 M Cr(III) by 0.1M Aliquat in CCl4 is easily achieved at room temperature, using 4.75M KNCS−0.05N HCl as aqueous phase. At high Cr(III) concentrations, the
complex anion present in the organic phase is Cr(NCS)
6
3−
; when working with dilute metal ion solutions, the species extracted is Cr(NCS)4 (H2O)
2
−
. Separations of mixtures containing 10−2−10−4 M Co(II), Ni(II) and Cr(III) have successfully been accomplished. 相似文献
79.
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
80.
From about 700 kg old, high altitude glacier ice (age 400 y) more than 170 glassy spherical objects with a mean diameter of 100 m were isolated. Neutron activation analysis of individual transparent objects (each 10–6 g) showed the presence of K, Sc, Cr, Fe, La, Eu, Au, etc., in varying concentrations. A detection limit of 10–14 g/g was achieved by means of an anticompton circuit. A systematic study by mass spectrometry of positive and negative ions using a LASER microprobe disclosed that the main constituents of some of these smooth glacier spheres consisted of elemental carbon. The chemical composition of some spherules admits the possibility of extraterrestrial origin, e.g. ablation material from meteorites with high carbon contents, which entered the earth's atmosphere. 相似文献