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991.
二安替比林基-4-羟基苯基甲烷及其与铬(Ⅵ)显色反应的研究 总被引:2,自引:0,他引:2
合成了二安替比林基-4-羟基苯基甲烷(DApHM),研究了它与铬(Ⅵ)的显色反应,建立了两个测定铬(Ⅵ)的新体系.在Mn(Ⅱ)和磷酸存在下,DApHM与 Cr(Ⅵ)反应生成橙红色产物,λ_max为435nm.CTMAB和Tween-80对该体系有明显增敏效果,其中CTMAB-DApHM-Cr(Ⅵ)体系ε为1.0 ×10~6;Tween-80-DApHM-Cr(Ⅵ)体系ε为6.9×10~5.Cr(Ⅵ)量在0.1~0.7μg/25mL间符合比尔定律.用于电镀废液和自来水中Cr(Ⅵ)的测定,结果满意. 相似文献
992.
993.
A new quantum chemical definition of oxidation number is proposed, in the present paper, as a direct generalization of the corresponding classical definition. According to the proposed general definition, the oxidation number can be calculated by use of molecular orbital data and a population analysis method or by use of other quantum chemical methods. For the practical calculation, we present a corresponding concrete calculation procedure within the framework of the maximum overlap population principle, which is very simple and very easy to use. The calculated numerical results are, on the whole, in good agreement with chemists' intuitive concepts of chemical bonding. 相似文献
994.
Photoinduced reactions of chloranil with 1,1-diarylethenes and product photochemistry-intramolecular 总被引:1,自引:0,他引:1
Photoinduced reactions of chloranil (CA) with 1,1-diarylethenes 1 [(p-X-Ph)(2)C=CH(2), X = F, Cl, H, Me] in benzene afforded products 4-14, respectively, with the bicyclo[4.2.0]oct-3-ene-2,5-diones 4, the 6-diarylethenylcyclohexa-2,5-diene-1,4-diones 5, and 2,3,5, 6-tetrachlorohydroquinone 13 as the major primary products. The cyclobutane products 4 are formed via a triplet diradical intermediate without involvement of single electron transfer (SET) between the two reactants, while 5 is derived from a reaction sequence with initial SET interaction between (3)CA and the alkene. The 9-arylphenanthrene-1,4-diones 6 and its 10-hydroxy-derivatives 7 are secondary photochemical products derived from 5. The isomeric cage products 9-11 are formed from 4 via intramolecular benzene-alkene [2 + 2] (ortho-)photocycloadditions induced by the triplet excited enedione moiety. The relative amount of the two groups of products (4 and its secondary products 9-11 via non-SET route vs 5 and its secondary products 6, 7, 8, 12, and 14 via SET route) shows a rather regular change, with the ratio of non-SET route products gradually increasing with the increase in oxidation potential of the alkenes and in the positive free energy change for electron transfer (DeltaG(ET)) between (3)CA and the alkene, at the expense of the ratio of the products from the SET route. The competition between the SET and non-SET routes was also found to be drastically influenced by solvent polarity, with the SET pathways more favored in polar solvent. Photo-CIDNP investigations suggest the intermediacy of exciplexes or contact ion radical pairs in these reactions in benzene, while in acetonitrile, SET process led to the formation of CA(*)(-) and cation radical of the alkene in the form of solvent separated ion radical pairs and free ions. 相似文献
995.
测量高聚物粘度的方法很多。对高粘度样品经常采用拉伸蠕变方法,这时测定的是拉伸粘度习η_T: σ=η_T(?)_f其中σ是拉伸应力,(?)_f是由此引起的拉伸流动的应变速率。由于高聚物是粘弹性材料。因此必须设法区分弹性形变和流动形变,才能得到η_T值。Bueche和Kraus等曾分别用拉伸蠕变方法研究聚甲基丙烯酸甲酯和聚顺丁二烯的本体粘度。他们所用的处理方法有三 相似文献
996.
Jin Yi Xu Qian Ran Wei Yi Hua Xiao Ming Wu Qiu Juan Wang Jing Zhang 《中国化学快报》2007,18(3):251-254
A series of 2-alkylbenzimidazole derivatives 9a-n have been designed and synthesized as a novel class of non-peptide angiotensin Ⅱ AT1 receptor antagonists. The synthesized compounds were evaluated for their antagonism of angiotensin Ⅱ, induced contraction in the rabbit thoracic aortic ring and the results showed that compounds 9a, 9g and 9j exhibited potent antagonistic activity of AT1 receptor. 相似文献
997.
Hong-wu Xu Lin Pin Jin-xia Li Zhong-ning Chen Ji-gui Wu 《Transition Metal Chemistry》2007,32(6):781-783
A novel heterohexanuclear complex [Ni2Ag4(μ-dppm)4(pymt)6](SbF 6)2 · 2DMF · H2O (1), was synthesized by self-assembly with [Ag2(μ-dppm)2(MeCN)2](SbF6) 2 and [Et4N][Ni(pymt)3] (dppm = bis(diphenylphosphino)methane, pymt = pyrimidine-2-thiolate) as components and characterized by IR spectra, elemental analysis,
1H-NMR spectrum, 31P-NMR spectrum and Visible-Ultraviolet spectrum. Structure of the complex was determined by X-ray analysis. 相似文献
998.
Xiufang Xu Yumei Xing Xia Yang Guichang Wang Zunsheng Cai Zhenfeng Shang Yinming Pan Xuezhuang Zhao 《International journal of quantum chemistry》2005,101(2):160-168
A total of eight possible isomers of C50O, an oxide of fullerene C50 (D5h), have been investigated by B3LYP/3‐21G calculations. The isomer, which has an annulene‐like structure with oxygen bridging across a [5,6] type C? C bond at the site between the pole and the equatorial belt, is found being the ground state of C50O. Four isomers are relatively more stable and the energy differences between them are not large. This result indicates that more than one C50O isomer will coexist once C50O is synthesized. The relative stabilities of the C50O isomers may be determined mainly by the strain release and by the formation of the cyclic phenylene substructure at the equatorial belt of the cage. The calculated nucleus independent chemical shifts (NICS) of the C50O isomers will be useful because from them one can expect outstanding NMR properties that can lead to their identification and characterization. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 相似文献
999.
1000.
A library of 1,2,3-triazoles, isoxazoles, 1,2,4-oxadiazoles, and isoxazoline-containing 1,2-di-heterocyclic-substituted compounds with three points of diversity linked by an E double bond were prepared. Key steps include a 1,3-dipolar cycloaddition and Porco's two-step, one-pot condensation and alpha-alkylation reaction of selenium resins. 相似文献