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11.
The thermal decomposition of zinc acetate dihydrate Zn(CH3CO2)2·2H2O in some humidity-controlled atmospheres has been successfully investigated by novel thermal analyses, which are sample-controlled thermogravimetry (SCTG), thermogravimety combined with evolved gas analysis using mass spectrometry (TG–MS) and simultaneous measurement of differential scanning calorimetry and X-ray diffractometry (XRD–DSC). The thermal processes of anhydrous zinc acetate in dry gas atmosphere by conventional linear heating experiment initiated with the sublimation around 180 °C, followed by the fusion and the decomposition over 250 °C. SCTG was useful to interpret clearly the successive reaction because the high-temperature parallel decompositions were effectively inhibited. The thermal behavior changed dramatically by introducing water vapor in the atmosphere and the thermal process was quite different from that in dry gas atmosphere. Zinc oxide (ZnO) was formed only in a humidity-controlled atmosphere, and could be easily synthesized at temperatures below 300 °C. XRD–DSC equipped with a humidity generator revealed directly the crystalline change from Zn(CH3CO2)2 to ZnO. A detailed thermal process of Zn(CH3CO2)2·2H2O and the effect of water vapor are discussed. 相似文献
12.
M. H. Wang Y. Sawada K. Saito S. Horie T. Uchida M. Ohtsuka S. Seki S. Kobayashi T. Arii A. Kishi T. Takahashi Y. Nishimoto T. Wakimoto K. Monzen I. Kashima T. Nishikiori L. X. Sun R. Ozao 《Journal of Thermal Analysis and Calorimetry》2007,89(2):363-366
The thermal change of the tris(8-hydroxyquinolinato)aluminum (Alq3) is currently investigated by XRD-DSC and TG. The phase transition of Alq3 from α-phase to γ-phase takes place at 643–669 K. A very sharp peak with the peak temperature at approx. 709 K is ascribed
to the melting of the Alq3. The decomposition of the Alq3 was observed accompanied with the melting and evaporation at >703K. The effect of the atmospheres on the mass loss procedure
was studied by TG. It was found that thermal process of Alq3 was strongly influenced by the partial pressure of water vapor in the atmosphere instead of oxygen. 相似文献
13.
Six new furostanol-type steroid saponins called trigoneosides Xa, Xb, XIb, XIIa, XIIb, and XIIIa were isolated from the seeds of Egyptian Trigonella foenum-graecum L. (Leguminosae) together with six known furostanol-type steroid saponins: trigoneosides Ia, Ib, and Va, glycoside D, trigonelloside C, and compound C. The structures of trigoneosides Xa, Xb, Xlb, XIIa, Xllb, and XIIIa were determined on the basis of chemical and physicochemical evidence as 26-O-beta-D-glucopyranosyl-(25S)-5alpha-furostane-2alpha+ ++,3beta,22xi,26-tetraol 3-O-alpha-L-rhamnopyranosyl(1-->2)-,beta-D-glucopyranoside, 26-O-beta-D-glucopyranosyl-(25R)-5alpha-furostane-2 alpha,beta,22xi,26tetraol 3-O-alpha-L-rhamnopyranosyl(l -->2)-beta-D-glucopyranoside, 26-O-beta-D-glucopyranosyl-(25R)-5alpha-furostane2alpha++ +,beta,22xi,26-tetraol 3-O-beta-D-xylopyranosyl(l -->4)-beta-D-glucopyranoside, 26-O-beta-D-glucopyranosyl-(25S)-furost-4-ene-3beta,22xi,26- triol 3-O-Ca-L-rhamnopyranosyl(1-->2)-beta-D-glucopyranoside, 26-O-beta-D-glucopyranosyl-(25R)-furost-4-ene-3beta,22xi+ ++,26-triol 3-O-alpha-L-rhamnopyranosyl(1-->2)-beta-D-glucopyranoside, and 26-O-beta-D-glucopyranosyl(25S)-furost-5-ene-3beta,22xi,26-t riol 3-O-alpha-L-rhamnopyranosyl(1-->2)-beta-D-glucopyranosyl (1-->3)-beta-D-glucopyranosyl(1--4)]-beta-D-glucopyranoside, respectively. 相似文献
14.
A high performance liquid chromatographic (HPLC) method for the quantification of 2-hydroxyfluorene (2-OHF) in normal human urine was established using deuterated 2-hydroxyfluorene (2-OHF-d9) as an internal standard with column-switching and fluorescence detection. The 2-OHF-d9 was synthesized by the metabolism of deuterated fluorene with cytochrome P450. The analytes were cleaned up on an ODS pre-column, via column-switching, and separated on an alkylamide-type reversed phase column. The internal standard eluted immediately prior to non-deuterated 2-OHF on the HPLC system and had nearly the same fluorescence characteristics as the non-deuterated 2-OHF. The detection limit was 0.03 nmol l(-1) (S/N = 3) and the calibration range of urine sample was from 0.2 to 50 nmol l(-1). The urine sample treatment involved enzymatic hydrolysis followed by solid phase extraction using a Sep-Pak C18 cartridge. 2-OHF was observed in the form of conjugates such as glucuronide and/or sulfate in human urine, and urinary metabolites were completely hydrolyzed for 2 h with beta-glucuronidase/aryl sulfatase. The proposed method was used to determine urinary 2-OHF in smokers and non-smokers, and showed that the urinary concentrations of 2-OHF in smokers were significantly higher than those in non-smokers (P < 0.01). Thus, the data suggest that urinary 2-OHF might be a sensitive and specific biological marker for the assessment of the exposure to polycyclic aromatic hydrocarbons. 相似文献
15.
Mitsuko Asai Eiji Mizuta Motowo Izawa Konomi Haibara Toyokazu Kishi 《Tetrahedron》1979,35(9):1079-1085
In this paper we report the isolation, chemical characterization and structural elucidation of Ansamitocin, a new antitumor antibiotic obtained from Nocardia No. C-15003 (N-1). Ansamitocin P-3, P-3' and P-4 with molecular formulae C32H43ClN2O9, C32H43ClN2O9 and C33H45ClN2O9, respectively, were identified as novel antibiotics. Their UV spectra resemble that of maytansine obtained from a plant source. Analysis of the PMR spectrum and spin-decoup studies of P-3 demonstrated that its skeletal structure was the same as that of maytansine. Reductive cleavage of each antibiotic gave maytansinol (P-0). Alkali hydrolysis of P-3, P-3' and P-4 gave isobutyric, butyric and isovaleric acids, respectively. P-3, P-3' and P-4 were concluded to be the isobutyrate, butyrate and isovalerate ester of maytansinol at C-3, respectively. An antitumor plant product, maytanacine, and its semisynthetic derivative, maytansinol propionate, were also produced by the same strain. 相似文献
16.
Masayuki Muroi Konomi Haibara Mitsuko Asai Kazuhide Kamiya Toyokazu Kishi 《Tetrahedron》1981,37(6):1123-1130
Macbecin I 1, C30H42N2O8, and macbecin II 2, C30H44N2O8, were shown to be 2,6-disubstituted benzoquinone and hydroquinone derivatives by an oxidation-reduction relationship, UV. 1H and 13C NMR spectra. Alkaline methanolysis of 1 gave a 2-aminobenzoquinone derivative 5, suggesting an ansa-structure for 1, and acid hydrolysis of 1 gave decarbamoyl products 9,10 and 11, indicative of the location of carbamoyloxy group in allylic position. Spin decoupling studies on 1,3 and 5clarified the partial structures [A], [B], [C] and [D]. From their mutual disposition two structures 1a and 1b, were proposed out of which 1a has been selected for the structure of 1 on the basis of the structure of oxidative degradation product 12. X-Ray analysis of the bromoacetyl derivative of 1 confirmed the above proposed structure and determined the absolute stereochemistry of 1 and 2. 相似文献
17.
Tautomeric structures of the title compounds in neutral and acidic media are discussed. In neutral solutions 3 and 4 exist as structure A and E, respectively. In weakly acidic methanol 3 exists as monocation H, whereas in aqueous solution as monocation G. In both strongly acidic aqueous and methanolic solutions 3 exists as dication K. On the other hand, 4 exists in weakly acidic and strongly acidic media as monocation L and dication M, respectively. The above conclusion can be extended to the 6-phenyl and 6-(3′-indolyl) derivatives of 3 as well as Cypridina luceferin (1) in aqueous and methanolic solutions. 相似文献
18.
Glow discharge polymerization between hexamethyldisilazane (HMDSZ) and trimethylsilyldimethylamine (TMSDMA) was compared by means of infrared spectroscopy and ESCA analysis. Infrared spectra pointed out differences in chemical structure between the polymers prepared from the two monomers, although the two polymers were mainly composed of resembling units such as Si? CH3, Si? CH2, Si? H, Si? O? Si, and Si? O? C groups: (i) The polymers prepared from TMSDMA contained N → O group, but the polymers from HMDSZ did not contain this group. (ii) Influences of the W/FM parameter (W is the input energy of rf power, F the flow rate of the monomer, and M the molecular weight of the monomer) appeared on decreasing the C? N group and increasing the C?O group in the TMSDMA system, but little influence appeared in the HMDSZ system. ESCA spectra (C1s, Si2p, and N1s core levels) supported the differences between the two polymers elucidated by infrared spectroscopy, and pointed out differences in susceptibility of the Si? N bond to plasma: The N? Si sequence of TMSDMA was completely ruptured in discharge to yield polymers, and the Si? NH? Si sequence of HMDSZ remained in considerable amount. 相似文献
19.
An automatic HPLC system for analyzing nitropolycyclic aromatic hydrocarbons (NPAHs, nitroarenes) in airborne particulates was previously described (Anal. Chim. Acta, 2001, 445, 20). Some problems with this system were that it generated a peak originating from an ascorbic acid solution that elutes at a retention time close to that of 1,6-dinitropyrene (DNP), and that it was able to analyze only 1,3-, 1,6-, 1,8-DNPs and 1-nitropyrene (I-NP). Here, we describe an improved system that effectively removes the interfering peak by introducing an ODS column just after the pump for the ascorbic acid solution, and which is capable of analyzing several additional compounds (2-, 4-NPs, 2-nitrofluorene. 6-nitrochrysene, 7-nitrobenz[a]anthracene, 3-nitroperylene and 6-nitrobenzo[a]pyrene etc.). The improved sensitivities were achieved by concentrating the compounds in a benzene-ethanol extract from airborne particulates, by increasing the loading time of the sample solution from 20 to 38 min, and by increasing the flow rate of an ascorbic acid solution from 1.3 to 1.8 mL/min. 相似文献
20.
Hwang IW Park M Ahn TK Yoon ZS Ko DM Kim D Ito F Ishibashi Y Khan SR Nagasawa Y Miyasaka H Ikeda C Takahashi R Ogawa K Satake A Kobuke Y 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(12):3753-3761
The excitation-energy-hopping (EEH) times within two-dimensional cyclic zinc(II)-porphyrin arrays 5 and 6, which were prepared by intermolecular coordination and ring-closing metathesis reaction of olefins, were deduced by modeling the EEH process based on the anisotropy depolarization as well as the exciton-exciton annihilation dynamics. Assuming the number of energy-hopping sites N = 5 and 6, the two different experimental observables, that is, anisotropy depolarization and exciton-excition annihilation times, consistently give the EEH times of 8.0 +/- 0.5 and 5.3 +/- 0.6 ps through the 1,3-phenylene linkages of 5 and 6, respectively. Accordingly, the self-assembled cyclic porphyrin arrays have proven to be well-defined two-dimensional models for natural light-harvesting complexes. 相似文献