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991.
The intergrowth of 1,10-decanedicarboxylic acid and urea give infinite hydrogen-bonded chains of the guest included in the hexagonal urea host. A deuterium high-resolution solid-state NMR study of the selectively deuterated intergrowth compound 1,10-decanedicarboxylic acid/hydrogenated urea at variable temperature in the range 90 < or = T < or = 300 K was performed on a single crystal. The analysis of the second moment as a function of temperature is shown to be compatible with the known phase transition occurring near T(c) = 203 K. Moreover, the spectra indicate that the orientational disorder is strong, and is compared to an axial uniform disorder. For this purpose, the general equation for the second moment of a system with uniform two-dimensional axial orientational disorder is given, and a method to take into account the non-uniform excitation of the pulse sequence is proposed. 相似文献
992.
Barontini F. Marsanich K. Cozzani V. 《Journal of Thermal Analysis and Calorimetry》2004,78(2):599-619
The TG-FTIR technique was used in the present study to investigate the thermal degradation behaviour of materials containing
brominated flame retardants under fire conditions. Time-temperature profiles and oxygen concentrations typical of selected
fire scenarios were reproduced in the thermogravimetric analyzer, while the characterization of the gaseous products generated
was performed by the simultaneous FTIR analysis. FTIR analysis combined with the use of specific calibration procedures allowed
the quantitative estimation of the gaseous products evolved as a function of experimental conditions. The results obtained
allowed the straightforward assessment and the comparison of the quantities of hydrogen bromide formed in the oxidation and
thermal degradation of pure brominated flame retardants and of flame retarded materials of industrial interest. Hydrogen bromide
yields resulted dependent on the experimental conditions used, such as oxygen concentration and heating rate. Although TG-FTIR
experiments only provide a representation of the actual heterogeneous combustion products in real fire conditions, the coupled
TG-FTIR technique proved to be a straightforward experimental methodology allowing one to obtain reference data on the nature
and quantities of the macropollutants generated in a fire.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
993.
Monitoring nitrite with optical sensing films 总被引:1,自引:0,他引:1
Ali A. EnsafiA. Kazemzadeh 《Microchemical Journal》2002,72(2):193-199
A new, low-cost nitrite sensor was developed by immobilizing a direct indicator dye in an optical sensing film for food and environmental monitoring. This sensor was fabricated by binding Safranine O to a cellulose acetate film that had previously been subjected to an exhaustive base hydrolysis. The membrane has good durability (>12 months) and a short response time (<8 s). Nitrite can be determined for the range of 0.005-2.00 μg ml−1 with 3δ detection limits of 0.001 μg ml−1. The method is easy to perform and uses acetylcellulose as a carrier. The reagents used for the activity of the cellulose support are inexpensive, non-toxic and widely available. 相似文献
994.
E. V. Tretyakov S. E. Tolstikov G. V. Romanenko Yu. G. Shvedenkov R. Z. Sagdeev V. I. Ovcharenko 《Russian Chemical Bulletin》2005,54(9):2169-2181
A new approach to the synthesis of polyfunctional pyrazolyl-substituted nitronyl nitroxides was developed based on the presynthesized
pyrazole derivatives prepared by 1,3-dipolar cycloaddition. The structures of the resulting mono-and biradicals were confirmed
by X-ray diffraction.
Dedicated to Academician A. L. Buchachenko on the occasion of his 70th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2105–2116, September, 2005. 相似文献
995.
996.
Shaul M. Aharoni 《先进技术聚合物》1995,6(6):373-382
The preparation of rigid aromatic, highly branched polyamides is described. Owing to the method of preparation and the chosen ratio of difunctional to trifunctional monomers, these entities are highly porous and not dendrimeric in nature. They better conform with the fractal model and are therefore called fractal polyamides (FPs). The effects of variations in the polymerization procedure, in total monomer concentration, in the ratio of amine to carboxyl groups and in the duration of the polycondensation reaction are investigated. Some characterization was performed and the results are presented and briefly discussed. 相似文献
998.
Kalevi Pihlaja Reijo Sillanpää Martti Dahlqvist Géza Stájer Markku Ahlgren 《Structural chemistry》1993,4(3):203-210
3-Oxo-1,3-oxathiane (1) and its monomethyl derivatives were prepared by oxidation of the corresponding 1,3-oxathianes. The structural analysis was carried out by1H and13C NMR, FTIR, and mass spectrometry. At 298 K compound1 was a 1 1 (at 173 K a 3 1) mixture of the SO(ax) and SO(eq) chair forms. The major oxidation products of methyl 1,3-oxathianes attained exclusively the SO(ax), Me(eq) chair forms except that of the 5-methyl derivative, which consisted of 7% of the SO(eq), Me(ax) chair conformation in CDCl3 solution. The minor products of oxidation existed in anancomeric SO(eq), Me(eq) chair conformations. The oxidation of 2-methyl- 1,3-oxathiane, however, led to 3,3-dioxo derivative (6) in addition to thetrans [SO(eq)] monoxide. The crystal structures of6 andtrans-3-oxo-5-methyl-1,3-oxathiane were solved by X-ray diffractometry. 相似文献
999.
1000.