共查询到20条相似文献,搜索用时 62 毫秒
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绿色化学与有机合成及有机合成中的原子经济性 总被引:28,自引:0,他引:28
本文概述了有机合成和绿色化学的关系, 并介绍了原子经济性的概念及其在有机合成中的重要性。对21 世纪的化学发展提出了希望。 相似文献
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火焰原子吸收光谱分析多元干扰体系中干扰效应的计算消除方法研究:I… 总被引:5,自引:0,他引:5
研究了火焰原子吸收光谱分析中多元混合干扰效应的计算消除方法,提出用多项式作为定量描述主测元素与干扰元素之间关系的通用数学模型,并对计算机自动寻找适宜的数学模型作了探讨。运用和尝试了一种新的下降算法-搜索法,本文是对多元统计方法在原子光谱分析中的应用的探索,在对多组分体系进行分析时,利用其元素间相互干扰时所形成的体系总吸光度与各级一分浓度间的函数关系,用增量法去形成所需的系数矩阵,从而实现了在产皮长 相似文献
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火焰原子吸收光谱法化学干扰研究的新进展 总被引:5,自引:1,他引:4
综述后10年火焰原子吸收光谱法中存在的化学干扰及消除方法的研究进展,评述了消除方法包括加入释放剂、保护剂、表面活性剂、络合剂、复合试剂和流动注射合并带法以及计算方法。共引用文献32篇。 相似文献
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Pingfan Li 《大学化学》2020,35(7):179-180
单原子催化,是由我国化学家提出的一个新概念,近年来在多相催化领域引领了一波研究热潮。单原子气体,是中学化学教育中的重要知识点。单原子催化这一术语,在文字上与单原子气体非常相似,但又有着完全不同的意义,存在一定的误导性,值得商榷。 相似文献
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温和条件下以CO2为原料制备高附加值化学品, 是CO2资源化利用的重要方法, 在众多CO2转化方法中, 电催化CO2还原(e-CO2RR)具有绿色、 清洁及条件可控等优势, 可以促进碳中和, 实现可持续发展. 然而, 由于其缓慢的动力学和较低催化剂活性, CO2电催化还原仍然存在低选择性, 低电流密度的问题. 单原子催化剂具有最大的原子利用率和明确定义的催化活性位点, 同时因其良好的配位结构和独特的电子结构极大地促进了CO2电催化还原的动力学过程, 是CO2电还原领域极具发展潜力的催化材料. 本文讨论了过渡金属和主族金属基单原子催化剂用于电催化CO2还原的研究进展, 系统总结了杂原子配位, 双/单原子位点, 金属-载体相互作用, 空间限域和分子桥联等策略调控单原子的微环境进而优化催化的性能, 揭示了单原子催化剂在 e-CO2RR领域内的突出优势和广阔的应用前景. 最后, 分析了单原子催化剂在CO2电催化转化过程中面临的挑战, 并对其未来进行了展望. 相似文献
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原子连接次序的一些经验规则 总被引:1,自引:0,他引:1
在有关物质分子结构的教学中 ,经常有学生问起一些类似这样的问题 :(1)次磷酸H3PO3与PF3是等电子体 ,H3PO3为什么具有 POHO OHH的四面体结构而不与PF3相似呈 P··HO OHOH的三角锥结构(2种结构式中的P都为 + 3氧化态 ,都是sp3杂化 ) ;(2 )N2 O为什么具有线性的··N—N—O· · ··· ·· ···结构 (方框表示π4 3键 ) ,但具有同样线性和键级的结构··N—O—N· ·· ·· ·· ···却不存在 (2种结构式中中心原子的N、O均为sp杂化 ) ;(3)CO与HCN也相当于等电子体 ,CO的结构… 相似文献
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HEPT类化合物的QSAR研究 总被引:3,自引:0,他引:3
为定量结构/活性相关性研究提取了量子化学参数,拓扑指数Am,分子连接性指数^mxt及疏水性常数,同时应用正交变换和最佳变量子集算法(Leaps-and-Bonds)进行了变量压缩和选择,进而实施了多元回归分析,并由此结果进行了HEPT类化合物(1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)-thymine derivatives)的结构/活性关系的理论解释,进行了人工神经网络法对于该类化合物的活性预测,其结构明显好于多元回归法。 相似文献
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V. P. Lezina N. A. Andronova L. D. Smirnov K. M. Dyumaev 《Chemistry of Heterocyclic Compounds》1971,7(11):1438-1440
The dependence of the chemical shifts of the ring protons on the pH of the medium for a number of 4-hydroxyquinoline derivatives was studied by means of PMR spectroscopy. The dipolar and uncharged hydroxy forms exist in equilibrium in aqueous solutions. The effect of intramolecular hydrogen bonding on the character of the dependence of the chemical shift on the pH of the medium in the case of 3-piperidinomethyl-4-hydroxyisoquinoline was investigated. The possibility of the separate protonation of the ring nitrogen and the side-chain nitrogen in 3-piperidinomethyl-4-hydroxyisoquinoline was established. The distribution of the -electron density in 4-hydroxyisoquinoline is in good agreement with its chemical behavior.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1546–1549, November, 1971 相似文献
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V. P. Lezina N. A. Andronova L. D. Smirnov K. M. Dyumaev 《Chemistry of Heterocyclic Compounds》1971,7(11):1433-1437
The dependence of the chemical shift of the ring protons on the pH of the medium for a number of 3-hydroxyquinoline derivatives was studied by PMR spectroscopy. The regions of ionization of the molecules, which correspond to the ranges of acidic, neutral, and alkaline media, were found. In D2O, 3-hydroxyquinoline is present only in the uncharged hydroxy form. The presence of intramolecular hydrogen bonding in 4-dimethylaminomethyl-3-hydroxyquinoline has a substantial effect on the character of the dependence of the chemical shift on the pH of the medium; the existence of separate protonation of the nitrogen atoms of the ring and the side chain of 4-dimethylaminomethyl-3-hydroxyquinoline was established. The distribution of the -electron density in the 3-hydroxyquinoline molecule is in good agreement with its chemical behavior during electrophilic substitution.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1540–1545, November, 1971. 相似文献
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通过在LS55型荧光-磷光-发光分光光度计上加装液滴产生及调节附件,采用计算机采集与分析处理数据,成功地研制了双通道液滴光化学传感装置.利用葡聚糖凝胶对复合维生素B中不同组分的选择性吸附来达到分离与同时检测的目的,并将其用于复合维生素B药片的分析,取得了满意的结果. 相似文献
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Tangney P 《The Journal of chemical physics》2006,124(4):044111
The theory underlying the Car-Parrinello extended-Lagrangian approach to ab initio molecular dynamics (CPMD) is reviewed and reexamined using "heavy" ice as a test system. It is emphasized that the adiabatic decoupling in CPMD is not a decoupling of electronic orbitals from the ions but only a decoupling of a subset of the orbital vibrational modes from the rest of the necessarily coupled system of orbitals and ions. Recent work [J. Chem. Phys. 116, 14 (2002)] has pointed out that, due to the orbital-ion coupling that remains once adiabatic decoupling has been achieved, a large value of the fictitious mass mu can lead to systematic errors in the computed forces in CPMD. These errors are further investigated in the present work with a focus on those parts of these errors that are not corrected simply by rescaling the masses of the ions. It is suggested that any comparison of the efficiencies of Born-Oppenheimer molecular dynamics (BOMD) and CPMD should be performed at a similar level of accuracy. If accuracy is judged according to the average magnitude of the systematic errors in the computed forces, the efficiency of BOMD compares more favorably to that of CPMD than previous comparisons have suggested. 相似文献
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