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931.
Lei Liu Wes Lee Cassandra R. Youshaw Mingbin Yuan Michael B. Geherty Peter Y. Zavalij Osvaldo Gutierrez 《Chemical science》2020,11(31):8301
A highly chemoselective iron-catalyzed three-component dicarbofunctionalization of unactivated olefins with alkyl halides (iodides and bromides) and sp2-hybridized Grignard reagents is reported. The reaction operates under fast turnover frequency and tolerates a diverse range of sp2-hybridized nucleophiles (electron-rich and electron-deficient (hetero)aryl and alkenyl Grignard reagents), alkyl halides (tertiary alkyl iodides/bromides and perfluorinated bromides), and unactivated olefins bearing diverse functional groups including tethered alkenes, ethers, protected alcohols, aldehydes, and amines to yield the desired 1,2-alkylarylated products with high regiocontrol. Further, we demonstrate that this protocol is amenable for the synthesis of new (hetero)carbocycles including tetrahydrofurans and pyrrolidines via a three-component radical cascade cyclization/arylation that forges three new C–C bonds.A highly selective iron-catalyzed three-component dicarbofunctionalization of unactivated alkenes with alkyl halides and sp2-hybridized Grignard reagents is reported. 相似文献
932.
Ab initio molecular orbital theory and density functional theory have been used to study nine isomers of N7 ionic clusters with low spin at the HF/6-31G*, MP2/6-31G*, B3LYP/6-31G*, and B3LYP/6-311(+)G* levels of theory. All stationary
points are examined with harmonic vibrational frequency analyses. Four N7
+ isomers and five N7
− isomers are determined to be local minima or very close to the minima on their potential-energy hypersurfaces, respectively.
For N7
+ and N7
−, the energetically low lying isomers are open-chain structures (C
2
v
and C
2
v
or C2). The results are very similar to those of other known odd-number nitrogen ions, such as N5
+, N9
+, and N9
−, for which the open-chain structures are also the global minima. This research suggests that the N7 ionic clusters are likely to be stable and to be potential high-energy-density materials if they could be synthesized.
Received: 16 July 2001 / Accepted: 8 October 2001 / Published online: 21 January 2002 相似文献
933.
o-Dianisidine (ODA)-H2O2-horseradish peroxidase (HRP) voltammetric enzyme-linked immunoassay system has firstly been used for the detection of tobacco mosaic virus (TMV). HRP catalyzes strongly the oxidation reaction of ODA by H2O2, the product of which produces a sensitive second order derivative linear sweep voltammetric peak at potential of −0.56 V (versus SCE) in Britton–Robinson (BR) buffer. HRP activity has been measured with this voltammetric peak and TMV detected through immunoreaction. The detection limit for HRP is 9.25×10-7 mU l−1 and the linear range is 2.5×10−6–5.0×10−4 mU l−1. The detection limit for the clarified TMV is 0.25 ng ml−1 and the highest dilution ratio detected for the infected leaf sap is 1:8×105. The sensitivity for TMV detection with this method is higher than that with the enzyme-linked immunosorbent spectrophotometric assay (ELISA) using ODA-H2O2-HRP system. The processes of the enzyme-catalyzed reaction and the electro-reduction of the product of the enzyme-catalyzed reaction have been described. 相似文献
934.
Enhanced and selective removal of mercury ions was achieved with chitosan beads grafted with polyacrylamide (chitosan-g-polyacrylamide) via surface-initiated atom transfer radical polymerization (ATRP). The chitosan-g-polyacrylamide beads were found to have significantly greater adsorption capacities and faster adsorption kinetics for mercury ions than the chitosan beads. At pH 4 and with initial mercury concentrations of 10-200 mg/L, the chitosan-g-polyacrylamide beads can achieve a maximum adsorption capacity of up to 322.6 mg/g (in comparison with 181.8 mg/g for the chitosan beads) and displayed a short adsorption equilibrium time of less than 60 min (compared to more than 15 h for the chitosan beads). Coadsorption experiments with both mercury and lead ions showed that the chitosan-g-polyacrylamide beads had excellent selectivity in the adsorption of mercury ions over lead ions at pH < 6, in contrast to the chitosan beads, which did not show clear selectivity for either of the two metal species. Mechanism study suggested that the enhanced mercury adsorption was due to the many amide groups grafted onto the surfaces of the beads, and the selectivity in mercury adsorption can be attributed to the ability of mercury ions to form covalent bonds with the amide. It was found that adsorbed mercury ions on the chitosan-g-polyacrylamide beads can be effectively desorbed in a perchloric acid solution, and the regenerated beads can be reused almost without any loss of adsorption capacity. 相似文献
935.
936.
OUH体系的结构和分析势能函数 总被引:3,自引:0,他引:3
采用密度泛涵B3LYP方法优化出了OUH分子的各种结构,确定了最稳定构型和离解能,以及它们的谐性力常数,并导出双原子分子UH,UO的Murrell-Sorbie势能函数及其光谱数据。采用多体项展式方法,导出OUH(X^4A')基态分子的分析势能函数,获得OUH(X^4A')体系的势能面,考察了这个势能函数的基本性质,正确地复现出OUH分子的平衡结构特征,结果表明:U+OH,O+UH,H+UO的反应均为无阈能的放热能反应。为进一步探讨OUH体系的反应动力学过程打下了基础。 相似文献
937.
Xiu-Lin Zeng Wang-Hua Chen Jia-Cong Liu Jin-Lin Kan 《Journal of Molecular Structure》2007,810(1-3):47-51
Three density-functional methods (B3P86, B3PW91, and B3LYP) are employed to investigate the O–NO2 bond lengths, frontier orbital energies, and O–NO2 bond dissociation energies (BDEs) of n-propyl nitrate (NPN), isopropyl nitrate (IPN), 2-ethylhexyl nitrate (EHN), triethylene glycol dinitrate (Tri-EGDN), and tetraethylene glycol dinitrate (Tetra-EGDN). It is found that the O–NO2 bond lengthens (destabilizes) in the order of IPN, NPN, EHN, Tetra-EGDN, and Tri-EGDN. From the data of frontier orbital energies (EHOMO, ELUMO), and energy gaps (ΔE), we estimate the relative thermal stability ordering of five nitrates and their corresponding radicals. The predicted BDEs of O–NO2 bond in NPN, IPN, EHN, Tri-EGDN, and Tetra-EGDN, are 176.6, 174.5, 168.1, 156.1, and 159.3 kJ mol−1, respectively. Based on the finding that the present results of BDEs are well coincident with the experimental results of apparent activation energies from the literature, we can draw a conclusion that the experimental thermolysis of five nitrates is only unimolecular homolytical cleavage of the O–NO2 bonds. 相似文献
938.
Wen-xun Guo Zong-li Shi Kui Liang Yan-li Liu Xian-hong Chen Wei Li 《Polymer Degradation and Stability》2007,92(3):407-413
New unsaturated polyesters of poly(fumaric acid-glycol-sebacic acid) copolymers and poly(maleic anhydride-glycol-sebacic acid) copolymers were prepared by melt polycondensation of the corresponding mixed monomers: sebacic anhydride, fumaric acid or maleic anhydride and glycol. Methyl-methacrylate (MMA) was used as crosslinker and dimer acid was used as thinner.In vitro studies showed that those copolymers are degradable in phosphate buffer at 37 °C and poly(fumaric acid-glycol-sebacic acid) has proper drug release rate as drug carriers. The biocompatibility of poly(fumaric acid-glycol-sebacic acid) copolymers under mice skin was also evaluated; macroscopic observation and microscopic analysis demonstrated that the copolymer is biocompatible and well tolerated in vivo. The injected poly(fumaric acid-glycol-sebacic acid) [molar ratio Mfumaric acid:Mglycol:Msebacic acid = 1.75:2.20:0.25] containing 5% adriamycin hydrochloride (ADM) in the mice bearing Sarcoma-180 tumor exhibited a good antitumor efficacy. The volume doubling time (VDT) (18 ± 2.5 days) of the tumor growth by this treatment was longer than that (7 ± 0.9 days) by the subcutaneous injection of ADM. 相似文献
939.
The coordination compounds of acctylacetonate-5,10,15,20-tctrasubstituted phcnyl-porphyrin with Yttrium, Y(o-Cl)Tppacac, Y(m- Cl)Tppacac, Y(p-Cl)Tppacac, Y(o-CH3O) Tppacac, and Y(p-CH3O)Tppacac (H2Tpp: tetraphcnylporphyrin, Hacac: acetylacctonc), were prepared and characterised on the basis of elemental analysis, infrared spectra, UV-visiblc spectra and thermal analysis. 相似文献
940.
The adsorptive stripping voltammetric determination of germanium(IV) based on the adsorptive accumulation of the germanium(IV)-pyrogallol complex on a hanging mercury drop electrode is reported. The reduction current of the adsorbed germanium complex is measured by differential-pulse cathodic stripping voltammetry. The peak potential is at -0.42 V vs. Ag AgCl (saturated KCL). The effects of various parameters (ligand concentration, supporting electrolytic composition and concentration, accumulation potential and collection time) on the response are discussed. With controlled accumulation for 3 min, the detection limit is 1.2 x 10(-9) M germanium. The relative standard deviation (at 1.2 x 10(-8) M germanium) is 3.6%. Possible interferences are evaluated. The applicability of the method to the determination of germanium(IV) in ore samples was also successfully carried out. 相似文献