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591.
López-Cara LC Carrión MD Camacho ME Gallo MA Espinosa A Choquesillo-Lazarte D Gonzalez-Pérez JM Entrena Guadix A 《Magnetic resonance in chemistry : MRC》2008,46(9):878-885
The (1)H and (13)C NMR resonances of 22 1-alkyl-pyrazole and 25 1-alkyl-pyrazoline derivatives were assigned completely using the concerted application of one- and two-dimensional experiments (DEPT, gs-HMQC and gs-HMBC). Nuclear Overhauser enhancement (NOE) effects, conformational analysis and X-ray crystallography confirm the preferred conformation of those compounds. 相似文献
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593.
In this work, a new 2-(2-oxoethyl)hydrazine carbothioamide modified silica gel (SG-OHC) sorbent was prepared and applied for preconcentration of trace mercury(II) prior to the measurement by inductively coupled plasma atomic emission spectrometry (ICP-AES). The optimization of some analytical parameters affecting the adsorption of the analyte such as acidity, shaking time, sample flow rate and volume, eluent condition, and interfering substances were investigated. At pH 3, the maximum static adsorption capacity of Hg(II) onto the SG-OHC was 37.5 mg g−1. The quantitative recovery (>95%) of Hg(II) could be obtained using 2 mL of 0.5 mol L−1 HCl and 1% CS(NH2)2 solution as eluent. Common coexisting substances did not interfere with the separation of mercury(II) under optimal conditions. The detection limit of present method was 0.10 ng mL−1, and the relative standard deviation (RSD) was lower than 4.0% (n = 8). The prepared sorbent was successfully applied for the preconcentration of trace Hg(II) in certified and water samples with satisfactory results. 相似文献
594.
苯甲酰肼在多壁碳纳米管修饰玻碳电极上的电催化氧化及其电化学动力学性质 总被引:1,自引:0,他引:1
研究了苯甲酰肼(BH)在MWCNT/GCE上的电化学行为。实验结果表明,BH在GCE上的直接电化学氧化十分迟缓,无氧化峰出现,但在MWCNT/GCE上BH在0.20 V处出现了一个不可逆氧化峰,且峰电流大幅度增大,表明MWCNT/GCE对BH电化学氧化具有良好的催化作用。同时用计时库仑法(Chro-nocoulometry,CC)和计时电流法(Chronoamperometry,CA)测定了电极过程动力学参数:扩散系数D=8.73×10-5cm2.s-1,电子转移系数α=0.85,电极反应速率常数kf=1.45×10-3s-1。稳态电流-时间实验结果表明,电流响应信号随其浓度成比例增长,响应时间小于6 s,最低响应浓度为1×10-6mol/L。该方法可用于BH电化学定量测定。 相似文献
595.
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597.
Dr. Benoît Crousse 《Chemical record (New York, N.Y.)》2023,23(9):e202300011
This review provides a recent overview of the different synthetic routes of the N-CF3 group. This scaffold can be prepared from the desulfurization of thiocabamoyl fluorides or isothiocyanates with fluoride ions. Electrophilic and radical trifluoromethylations are also a great way to generate this motif. This report also focuses on the valorization of some N-CF3 compounds, which leads to new unknown N-trifluoromethyl derivatives. Finally, the first metabolic stability studies will be given for certain structures. 相似文献
598.
《Arabian Journal of Chemistry》2023,16(5):104687
Newly synthesized benzoyl kappa carrageenan (Bz-?car) was successfully produced by the Friedel Craft acylation method. The successful substitution of benzoyl molecule into kappa carrageenan (?car) polymeric chain was confirmed by the FTIR analysis based on the formation of new carbonyl (CO) and CC bonds in Bz-?car. 1H NMR analysis further proved the benzoylation by the appearance of new multiple resonances peaks at δ = 6.6–9.50 ppm, which belonged to the characteristic signals of protons in the aromatic benzoate group. XRD analysis showed reduced crystallinity of the synthesised carrageenan, while elemental analyser analysis revealed the increased percentages of carbon in Bz-?car upon the substitution. The highest degree of substitution obtained was 0.27. TGA showed lower degradation temperature in the synthesised carrageenan, while water contact angle analysis demonstrated that Bz-?car was less hydrophilic as compared to the pristine ?car. Solubility tests showed that Bz-?car was best dissolved in ethylene glycol. The benzoylation also improved the ionic conductivity of Bz-?car to 3.10 × 10?4 Scm?1 at ambient temperature. 相似文献
599.
Density functional theory has been used to elucidate the mechanistic underpinnings of the regeneration of ammonia-borane (H3B−NH3, AB ) from polyborazylene (BxNxHx, PBz ) in the presence of hydrazine (H2N−NH2, Hz ). Herein, borazine (B3N3H6, Bz ) is used as the simplest relevant model of PBz for the regeneration process. Digestion of Bz using Hz was found to occur by a string of Lewis acid base adduct (between B atoms of Bz and Hz molecule) formation and Hz assisted proton transfer processes. Later, B−H bonds of HB(NHNH2)2, the Bz digested product, are redistributed to form hydrazine-borane (H3B−NH2NH2, HzB ) and B(NHNH2)3. Redistribution of B−H bonds occurs through hydroboration and concerted proton-hydride transfer. Another B−H redistributed product, B(NHNH2)3, produces HzB as a result of proton and hydride transfer from cis-diazene ( Dz ), the oxidized product of Hz in presence of O2. 相似文献
600.
《Mendeleev Communications》2023,33(2):203-205
Novel β-arylethylamines bearing 5-pyrazolone substituent in the ortho-position of aryl moiety were obtained by the hydrazine-induced recyclization of 1-(alkoxycarbonyl-methylidene)-1,2,3,4-tetrahydroisoquinolines. These amines can exist in a highly unstable betaine form in the solid phase. 相似文献