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61.
Ji-Lai Li Cai-Yun Geng Xu-Ri Huang Chia-Chung Sun 《Theoretical chemistry accounts》2007,117(3):417-429
The reaction of atomic radical F with propyne has been studied theoretically using ab initio quantum chemistry methods and
transition state theory. The potential energy surface was calculated at the CCSD(T)/aug-cc-pVDZ (single-point) level using
the UMP2/6-311++G(d,p) optimized structures. Two reaction mechanisms including the addition–isomerization–elimination reaction
mechanism and the directed hydrogen abstraction reaction mechanism are considered. For the hydrogen abstraction reactions,
i.e., the most probable evolution pathway in the title reaction, the HF formation occurs via direct abstraction mechanism
dominantly and the H atom picked up by the atomic radical F should come mostly from the methyl group of normal propyne. On
the other hand, for the addition–isomerization–elimination mechanism, the most feasible pathway should be the atomic radical
F attacking on the C≡C triple bond in propyne (CH3C≡CH) to form a weakly-bound adduct A1 with no barrier, followed by F addition to the C≡C triple bond to form the low-lying
intermediate isomer 5. Subsequently, isomer 5 directly dissociates to P3 H2CCCHF + H via transition state TS5/P3. The other reaction pathways on the doublet PES are less competitive due to thermodynamical or kinetic factors. Furthermore,
based on the analysis of the kinetics of all channels through which the addition and abstraction reaction proceed, we expect
that the competitive power of reaction channels may vary with experimental conditions for the title reaction. The present
work will provide useful information for understanding the processes of atomic radical F reaction with other unsaturated hydrocarbons.
This material is available from author via E-mail. 相似文献
62.
《Electroanalysis》2003,15(3):225-229
The interaction between avidin and biotin was evaluated electrochemically by monitoring the change in the electrode response of redox markers. Biotin was immobilized on the electrode surface by means of the electrochemical polymerization of biotinylated pyrrole and pyrrole. When avidin was introduced onto the biotinylated polypyrrole electrode surface, the large change in the electrode response of the redox marker was detected. The fact that the change in the electrode response of a marker ion could be attributed to the electrostatic interaction between avidin on the electrode surface and the redox marker ion present in a solution was verified by replacing avidin with NutrAvidin. At a pH lower than the isoelectric point of avidin, the electrode response of ferrocyanide as an anionic marker ion increased linearly within the range of 5.0×10?9 ?3.0×10?8 M avidin. The relative standard deviation at 1.5×10?8 M avidin was about 5.4% (n=5). The detection of biotin was also performed using a competitive reaction between biotin in solution and biotin that had been immobilized on the electrode surface in the form of the biotinylated polypyrrole. 相似文献
63.
Katarina D. Karljiković Branislava S. Stanković Emil B. Milosavljević Zlatko J. Binenfeld 《Monatshefte für Chemie / Chemical Monthly》1986,117(5):661-670
Mixed acidic constants (pK
a
) of quinolinium oximes [1-(2-phenyl-2-hydroxyiminoethyl)-1-quinolinium chloride (F-1), 1-(2-phenyl-2-hydroxyiminoethyl)-1-isoquinolinium chloride (F-2), 1-(2-phenyl-2-hydroxyiminoethyl)-1-(4-methyl)-quinolinium chloride (F-3), and 1-(2-phenyl-2-hydroxyiminoethyl)-1-(6-methyl)-quinolinium chloride (F-4)] have been determined via their UV absorption spectra recorded in the series ofBritton-Robinson's buffer solutions in thepH region 8.74–11.28 (t=25±0.5°C, =0.2). The obtainedpK
a
values are in good agreement with those achieved by applying graphical methods. The followingpK
a
values have been obtained: 9.93 forF-1, 9.90 forF-2, and 10.02 forF-3 andF-4.On the basis of potentiometric titrations thermodynamic acidic constants (pK
a
) of compoundsF-1,F-2,F-3, andF-4 have been determined and they were found to be 9.82, 9.71, 9.91, and 9.86, respectively. The values obtained by transferringpK
a
intopK
a
are in good agreement with the values obtained spectrophotometrically.
Bestimmung der Aciditätskonstanten einiger Phenyl-hydroxyiminoethylchinolin-Verbindungen
Zusammenfassung Die Mischaciditätskonstanten (pK a ) der Chinolin-Oxime 1-(2-Phenyl-2-hydroxyiminoethyl)-1-chinolinium chlorid (F-1), 1-(2-Phenyl-2-hydroxyiminoethyl)-1-isochinolium chlorid (F-2), 1-(2-Phenyl-2-hydroxyiminoethyl)-1-(4-methyl)-chinolinium chlorid (F-3) und 1-(2-Phenyl-2-hydroxyiminoethyl)-1-(6-methyl)-chinolinium chlorid (F-4) wurden durch ihre UV-Absorptionspektren in einer Reihe vonBritton-Robinson-Pufferlösungen impH-Intervall 8.74–11.28 (t=25±0.5°C; =0.2) bestimmt. Die berechnetenpK a -Werte stimmen mit den über graphische Methoden erhaltenen Ergebnissen überein. DerpK a -Wert beträgt 9.93 für die VerbindungF-1 und 9.90 fürF-2, sowie 10.02 fürF-3 andF-4.Auf Grund der potentiometrischen Titration wurden auch die thermodynamischen Aciditätskonstanten (pK a ) berechnet: 9.82 fürF-1, 9.71 fürF-2, 9.91 fürF-3 und 9.86 fürF-4. Wenn man diese Konstanten in Mischaciditätskonstanten überträgt, erhält man Werte, die mit den durch spektrophotometrischen Bestimmungen erhaltenen Werten gut übereinstimmen.相似文献
64.
Potential energy surfaces for rotations around two central CN bonds in N-(deoxyguanosin-8-yl)-2-acetylaminofluorene (AAF–dG) and its deacetylated derivative (AF–dG) were studied using Amber 95 molecular mechanics. Both of these adducts are known to be strong mutagens and carcinogens. New Amber 95 force field parameters were derived for the linkage connecting guanine and fluorene moieties in AAF–dG and AF–dG. For this purpose, we determined ab initio MP2/cc-pVDZ//B3-LYP/6-31G* and polarized continuum model Hartree–Fock/6-31G* potential energy surfaces of smaller model systems that included the N-methylimidazole–acetylaniline and N-methylimidazole–aniline adducts. The molecular mechanics parameters were adjusted to minimize differences between the gas-phase ab initio and molecular mechanics surfaces of these model systems. The resulting parameters were transferred to AF–dG and AAF–dG. The barrier for the rotation of the fluorene residue in AF–dG was found to be less than 2 kcal/mol. Such a small barrier renders the fluorene moiety freely rotatable at room temperature. In contrast, the fluorene rotation in AAF–dG is hindered by a significantly larger barrier of 10 kcal/mol. This barrier corresponds to conformations in which the fluorene and acetyl groups lie in the same plane, and is largely due to steric repulsion. Similarly, the coplanar arrangement of guanine and the bridging amino or acetyl groups is disfavored by 5–10 kcal/mol, with AAF–dG again being the more rigid of the two molecules. Energy minima for a rotation around a bond between guanine and the bridging nitrogen are found at ±80° in AAF–dG, and at 120° and –90° for AF–dG. Overall, the fluorene–dG linkages in AF–dG and AAF–dG adducts have significantly different equilibrium structures and torsional flexibilities. These differences may be contributing factors for the observed disparity in mutagenic effects of these adducts.Electronic Supplementary Material: Supplementary material is available in the online version of this article at Acknowledgements. This work was supported by the NSF REU grant no. CHE-0243825 to Loyola University Chicago. We thank to Tom Ellenberger and Shuchismita Dutta for providing us with their results prior to publication. 相似文献
65.
Michael I. Bruce Mark A. Buntine Benjamin G. Ellis Paul J. Low Brian W. Skelton 《Journal of organometallic chemistry》2004,689(21):3308-3326
The preparation of several ruthenium complexes containing cyanocarbon anions is reported. Deprotonation (KOBut) of [Ru(NCCH2CN)(PPh3)2Cp]PF6 (1) gives Ru{NCCH(CN)}(PPh3)2Cp (2), which adds a second [Ru(PPh3)2Cp]+ unit to give [{Ru(PPh3)2Cp}2(μ-NCCHCN)]+ (3). Attempted deprotonation of the latter to give the μ-NCCCN complex was unsuccessful. Similar chemistry with tricyanomethanide anion gives Ru{NCC(CN)2}(PPh3)2Cp (4) and [{Ru(PPh3)2Cp}2{μ-NCC(CN)CN}]PF6 (5), and with pentacyanopropenide, Ru{NCC(CN)C(CN)C(CN)2}(PPh3)2Cp (6) and [{Ru(PPh3)2Cp}2{μ-NCC(CN)C(CN)C(CN)CN}]PF6 (7). The Ru(dppe)Cp* analogues of 6 and 7 (8 and 9) were also prepared. Thermolysis of 6 (refluxing toluene, 12 h) results in loss of PPh3 and formation of the binuclear cyclic complex {Ru(PPh3)Cp[μ-NC{C(CN)C(CN)2}CN]}2 (10). The solid-state structures of 2-4 and 8-10 have been determined and the nature of the isomers shown to be present in solutions of the binuclear cations 7 and 9 by NMR studies has been probed using Hartree-Fock and density functional theory. 相似文献
66.
CO2选择性氧化甲烷制C2烃催化剂La2O3/ZnO的氧化还原和CO2吸附性能 总被引:6,自引:0,他引:6
La2O3/ZnO催化剂体系在以二氧化碳作为氧化剂的甲烷氧化偶联反应中具有很高的C2烃选择性和稳定性.采用CO2-TPD-MS和TPR技术考察了La2O3/ZnO对CO2的吸附性质及其氧化还原行为.结果表明:(1)La2O3/ZnO催化剂体系存在着强、弱两种碱中心,其中弱碱中心数量随样品中La2O3含量增加而减少,强碱中心强度随样品中La2O3含量增加而增强.(2)由于组分相互作用,高温下,La2O3/ZnO易产生晶格氧空位,使之对CO2的吸附增强,吸附后的CO2与晶格氧作用形成立方晶型La2O2CO3.(3)La2O3/ZnO表面的La3+和Zn2+可以部分被还原,由于组分间的相互作用,使得二者的还原都较单一组分存在时更难.(4)H2-CO2-H2氧化还原循环实验表明,La2O3/ZnO表面被部分还原后,CO2可以将部分被还原的表面再氧化.在此基础上对La2O3/ZnO催化剂上甲烷与CO2转化为C2烃的机制也进行了讨论. 相似文献
67.
G. Chambaud W. Gabriel T. Schmelz P. Rosmus A. Spielfiedel N. Feautrier 《Theoretical chemistry accounts》1993,87(1-2):5-17
Summary The three-dimensional potential energy functions have been calculated from highly correlated multireference configuration interaction electronic wavefunctions for theX
3
B
1,a
1
A
1, andb
1
B
1 states of the NH
2
+
ion. For the quasi-linear electronic ground state this information and the electric dipole moment functions have been used to calculate spectroscopic constants, line intensities and rotationally resolved absorption spectra. For thea
1
A
1-b
1
B
1 bent/quasi-linear Renner-Teller system ro-vibronic energy levels have been obtained from a variational approach accounting for anharmonicity, rotation-vibration and electronic angular momenta coupling effects. The vibronic levels are given for energies up to 13 500 cm–1 for the bending levels and up to 8000 cm–1 for the stretching and combination levels.Dedicated in the honor of Prof. Werner Kutzelnigg 相似文献
68.
Maksymilian Ignaczak Andrzej Grzejdziak 《Monatshefte für Chemie / Chemical Monthly》1986,117(10):1123-1132
The values of standard potentials of redox systems formed by the complexes of Ag(II) and Ag(I) with 2,2-bipyridine and 1,10-phenanthroline in acetonitrile have been determined. The properties of the above systems in water and acetonitrile are compared. The possibility of application of these systems for the construction of electrodes with a constant potential in different solvents is discussed.
Charakteristik der Systeme Ag(bipy) 2 2+ /Ag(bipy) 2 + und Ag(phen) 2 2+ /Ag(phen) 2 + in Acetonitril
Zusammenfassung Die Standardpotentialwerte der Redoxsysteme, die durch Komplexbildung von Ag(II)- und Ag(I)-Ionen mit 2,2-Bipyridin und 1,10-Phenantrolin gebildet werden, wurden in Acetonitril bestimmt. Die Eigenschaften dieser Redoxsysteme in Wasser und Acetonitril wurden verglichen.Es wurde weiterhin die Möglichkeit der Anwendung dieser Systeme zur Konstruktion einer Elektrode mit unveränderbarem Potential in verschiedenen Lösungsmitteln diskutiert.相似文献
69.
氧化-还原低温引发甲基丙烯酸甲酯/丙烯酸丁酯超浓乳液聚合研究 总被引:10,自引:0,他引:10
以乳化剂十二烷基硫酸钠 (SDS)和共乳化剂十六烷醇 (HD)作为复合乳化体系 ,过氧化二苯甲酰(BPO)和N ,N 二甲基苯胺 (DMA)作为氧化还原引发体系 ,甲基丙烯酸甲酯 丙烯酸丁酯 (MMA BA)作为混合单体 ,制备了分散相占 83 %以上的稳定的超浓乳液 ,然后在低温下引发聚合 .探讨了引发剂浓度、氧化剂与还原剂的摩尔比、乳化剂的浓度、液膜增强剂的种类、聚合温度等因素对聚合稳定性和聚合速率的影响 ,测定并计算得到了聚合速率的公式 ;用激光散射粒度分布仪测定了聚合物乳胶粒子的大小及粒径分布 ,用透射电子显微镜观察了聚合物乳胶粒的形态 ,讨论了乳化剂浓度、聚合温度等对乳胶粒形态、大小的影响 相似文献
70.
Many studies have focused on effective ways to exploit enzyme immobilization on an electrode surface to help improve the performance of enzymatic electrochemical biosensors. Herein, a novel glucose sensor was fabricated by immobilizing glucose oxidase (GOx) onruthenium-based conjugated polymer (CP) and metal-organic framework (MOF) nanocomposites. This has not only reduced the applied potential to 0.2 V (vs. Ag/AgCl), but also improved the effective surface area for enzyme immobilization.PPG@Ru@UiO-66-NH2 was tailored by controlled chemical synthesis from a pre-synthesized water-soluble conjugated polymer (poly(N-phenylglycine)) and metal-organic framework (UiO-66-NH2). The resulting nanocomposites were characterized using Fourier transform infrared spectroscopy, X-ray fluorescence, scanning electron microscopy, and cyclic voltammetry. The PPG@Ru@UiO-66-NH2/GOx coated electrodedisplayed a linear measurementrange for glucose from 1 mM to 10 mM, with a sensitivity of 45.92 μA ⋅ mM−1cm−1 and limit of detection of5 μM( ). Furthermore, the practical application of the fabricatedglucosesensor was tested in simulative blood samples with satisfactoryaccuracy. This approach alsoopens a new door for applications regarding both enzymatic electrochemical biosensors and enzymatic biofuel cells (EBFCs). 相似文献