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Scan rate and concentration dependence of the voltammograms of substituted phenols on electrodes with different size, diffusion coefficients of phenols in different solvents 取代苯酚在不同尺寸电极上的扫描速率和浓度依赖性,苯酚在不同溶剂中的扩散系数
IF 1.1 4区 化学 Q3 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2023-02-24 DOI: 10.1139/cjc-2022-0096
L. Kiss, S. Kunsági-Máté
In this work, the effects of the scan rate and the concentration of the substituted phenols on the peak currents or current plateaus have been investigated. Voltammetric curves recorded by a platinum microelectrode varied significantly under different experimental conditions in cases of 4-chlorophenol, 4- tert-butylphenol, and 4-nitrophenol. In the case of 4-methoxyphenol and 4- tert-butylphenol, when the experiments were performed in the lower concentration range in acetonitrile, the plateau current and peak current showed linear dependence on phenol concentration. Therefore, these ranges offer opportunity for further characterization. The electrode reaction of 4-methoxyphenol was found to be a diffusion-controlled process in the solvents applied (water, acetonitrile, dimethyl sulfoxide, dimethyl formamide, nitrobenzene, acetone, dichloromethane, methanol, ethanol, 1-propanol, 1-butanol, and 1-pentanol). Diffusion coefficients of 4-methoxyphenol were determined with a microelectrode using the steady-state voltammograms. Diffusion coefficients of other phenols were measured only in acetonitrile with a macroelectrode. In agreement with known theories, the diffusion coefficients showed inversely proportional relationships with the solvent viscosities. Special care was needed in 1-pentanol solvent since the increasing anodic peaks appeared after the first scan and overlaid with the sigmoidal-shaped regular microelectrode voltammograms. This observation is probably due to formation of adhering residual electroactive products.
在这项工作中,研究了扫描速率和取代酚的浓度对峰值电流或电流平台的影响。在4-氯苯酚、4-叔丁基苯酚和4-硝基苯酚的不同实验条件下,铂微电极记录的伏安曲线变化显著。以4-甲氧基苯酚和4-叔丁基苯酚为例,在乙腈中较低浓度范围内进行实验时,平台电流和峰值电流与苯酚浓度呈线性关系。因此,这些范围为进一步表征提供了机会。4-甲氧基苯酚的电极反应在不同溶剂(水、乙腈、二甲基亚砜、二甲基甲酰胺、硝基苯、丙酮、二氯甲烷、甲醇、乙醇、1-丙醇、1-丁醇和1-戊醇)中呈扩散控制过程。采用稳态伏安法测定了4-甲氧基苯酚的扩散系数。其他酚类化合物仅用大电极在乙腈中测定扩散系数。与已知理论一致,扩散系数与溶剂粘度呈反比关系。在1-戊醇溶剂中需要特别注意,因为在第一次扫描后出现了增加的阳极峰,并与s型规则微电极伏安图重叠。这种观察结果可能是由于粘接残余电活性产物的形成。
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引用次数: 0
Synthesis of 1,2,4,5-oxadiazaboroles by three-component condensations of hydroxylamines, nitriles, and diarylborinic acids 羟胺、腈和二酰基硼酸三组分缩合合成1,2,4,5-恶二唑硼醚
IF 1.1 4区 化学 Q3 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2023-02-23 DOI: 10.1139/cjc-2022-0200
Zhenlu Ge, A. Lough, M. Taylor
A method for the synthesis of substituted 1,2,4,5-oxadiazaboroles is described, in which hydroxylamines, nitriles, and diarylborinic acids engage in a three-component condensation reaction. The protocol provides access to a substitution pattern that is not readily available through other methods—namely, 2,3-disubstitution, with a tetracoordinate boron center. Structures of representative members of this class of heterocycles were determined by single crystal X-ray diffraction analysis.
描述了一种合成取代的1,2,4,5-恶二唑硼的方法,其中羟胺,腈和二烷基硼酸参与三组分缩合反应。该方案提供了通过其他方法难以获得的取代模式,即具有四配位硼中心的2,3-二取代。用单晶x射线衍射分析确定了这类杂环化合物的代表性分子的结构。
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引用次数: 0
Convenient access to β-substituted cysteines and β- and γ-mercapto prolines 方便地获得β-取代半胱氨酸和β-和γ-巯基脯氨酸
IF 1.1 4区 化学 Q3 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2023-02-15 DOI: 10.1139/cjc-2022-0161
Jacob C. Hansen, Marco Rabuffetti, L. Bunch
Herein we describe a convenient method for the synthesis of the β-substituted Cys analogs 1a, b and trans-β-mercapto proline 1c, from their corresponding α,β-unsaturated-α-amino esters using p-methoxybenzyl mercaptan as the sulfur source. The intermediate β-thioethers are stable toward chromatographic purification, and after global deprotection the β-mercapto amino acids 1a–c are obtained in good to high yields (64%–99%).
本文介绍了一种以对甲氧苄硫醇为硫源,以α、β-不饱和α-氨基酯为原料,合成β-取代的半胱氨酸类似物1a、b和反式β-巯基脯氨酸1c的简便方法。中间体β-硫醚在色谱纯化方面是稳定的,经过全局脱保护后得到的β-巯基氨基酸1a-c收率较高(64%-99%)。
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引用次数: 0
Dicarbon defect in hexagonal boron nitride monolayer - a theoretical study 六方氮化硼单层碳缺陷的理论研究
IF 1.1 4区 化学 Q3 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2023-02-15 DOI: 10.1139/cjc-2022-0291
T. Korona, J. Jankowska, Emran Masoumifeshani
A comprehensive theoretical study of the lowest electronic vertical excitations of the CBCN defect in the monolayer of hexagonal boron nitride has been performed. Both the periodic boundary conditions approach and the finite-cluster simulation of the defect have been utilized at the density-functional theory (DFT) level. Clusters of increasing sizes have been used in order to estimate artefacts resulting from edge effects. The stability of the results with respect to several density functionals and various basis sets has been also examined. High-level ab initio calculations with methods like EOM-CCSD, ADC(2), and TD-CC2, were performed for the smallest clusters. It turns out that TD-DFT with the CAM-B3LYP functional gives similar lowest excitation energies as EOM-CCSD, ADC(2), and TD-CC2. The lowest excitation energies resulting from the periodic-boundary calculation utilizing the Bethe-Salpeter equation are in agreement with the results for finite clusters. The analysis of important configurations and transition densities shows that for all studied methods, the lowest excited state is localized on two carbon atoms and their closest neighbours and has a large dipole transition moment. The optimized geometries for the lowest two excited states indicate that in both cases the carbon-carbon bond becomes a single bond, while for the second excited state additionally one from boron-nitrogen bonds looses its partially double character. The calculation of the excitation energies at the respective optimal geometry reveals that these two energies become about 0.5 eV lower than vertical excitations from the ground-state geometry.
本文对六方氮化硼单层中CBCN缺陷的最低电子垂直激发进行了全面的理论研究。在密度泛函理论(DFT)水平上,利用周期边界条件方法和有限簇模拟缺陷。为了估计由边缘效应产生的伪影,已经使用了尺寸不断增加的簇。本文还检验了结果对几种密度泛函和各种基集的稳定性。使用EOM-CCSD、ADC(2)和TD-CC2等方法对最小的簇进行高级从头计算。结果表明,具有CAM-B3LYP泛函的TD-DFT具有与EOM-CCSD、ADC(2)和TD-CC2相似的最低激发能。利用Bethe-Salpeter方程的周期性边界计算得到的最低激发能与有限簇的结果一致。对重要构型和跃迁密度的分析表明,在所有研究方法中,最低激发态都定位于两个碳原子及其最近邻,并且具有较大的偶极子跃迁矩。最低两个激发态的优化几何结构表明,在这两种情况下,碳碳键都变成了单键,而在第二激发态中,硼氮键失去了部分双键特征。在各自最优几何形状下的激发能计算表明,这两个能量比基态几何形状的垂直激发低约0.5 eV。
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引用次数: 1
Do we need delocalised wavefunctions for the excited state dynamics of 1,1-difluoroethylene? 1,1-二氟乙烯的激发态动力学需要离域波函数吗?
IF 1.1 4区 化学 Q3 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2023-02-14 DOI: 10.1139/cjc-2022-0267
Sandra G'omez, N. Singer, L. Gonz'alez, G. Worth
In this work we set up a model Hamiltonian to study the excited state quantum dynamics of 1,1-difluoroethylene, a molecule that has equivalent atoms exchanged by a torsional symmetry operation leading to equivalent minima on the potential energy surface. In systems with many degrees of freedom where the minimum energy geometry is not unique, the ground state wavefunction will be delocalised among multiple minima. In this small test system, we probe the excited state dynamics considering localised (in a single minimum) and delocalised (spread over among multiple minima) wavefunctions and check whether this choice would influence the final outcome of the quantum dynamics calculations. Our molecular Hamiltonian comprises seven electronic states, including valence and Rydberg states, computed with the MS-CASPT2 method and projected onto the vibrational coordinates of the twelve normal modes of 1,1-difluoroethylene in its vibrational ground state. This Hamiltonian has been symmetrised along the torsional degree of freedom to make both minima completely equivalent and the model is supported by the excellent agreement with the experimental absorption spectrum. Quantum dynamics results show that the different initial conditions studied do not appreciably affect the excited state populations or the absorption spectrum when the dynamics is simulated assuming a delta pulse excitation. Future work will look at whether initial superpositions can be formed that guide the system, e.g. to a single minimum.
在这项工作中,我们建立了一个模型哈密顿量来研究1,1-二氟乙烯的激发态量子动力学,该分子具有通过扭转对称操作交换的等效原子,导致势能表面上的等效极小值。在多自由度系统中,最小能量几何不是唯一的,基态波函数将在多个最小值之间离域。在这个小型测试系统中,我们考虑局域(在单个最小值中)和非局域(分布在多个最小值中)波函数来探测激发态动力学,并检查这种选择是否会影响量子动力学计算的最终结果。我们的分子哈密顿量包括7个电子态,包括价态和里德堡态,用MS-CASPT2方法计算,并投影到1,1-二氟乙烯在振动基态的12个正态的振动坐标上。该哈密顿量沿扭转自由度对称,使两个极小值完全等效,模型与实验吸收光谱非常吻合。量子动力学结果表明,当采用δ脉冲激励模拟动力学时,所研究的不同初始条件对激发态居群或吸收光谱没有明显影响。未来的工作将着眼于是否可以形成引导系统的初始叠加,例如单个最小值。
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引用次数: 0
Predicting Reaction Barriers in Solid-State Systems Under Stress via Second-Order Energy Expansion 利用二阶能量膨胀预测应力下固体体系的反应势垒
IF 1.1 4区 化学 Q3 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2023-02-14 DOI: 10.1139/cjc-2022-0278
L. Laverdure, N. Mosey
Solid state transformations are important in many areas of science and technology. Herein, a model for predicting the relative energies of stationary points along the reaction pathways for stress-induced solid state transformations is assessed and applied. The model is based on a second-order expansion of the energy of the system with respect to changes in the unit cell, and requires a small number of parameters that can be obtained through quantum chemical calculations. Comparison of the model with the results of quantum chemical calculations indicates that the model accurately reproduces changes in energy occurring during stress-induced transformations over a reasonable range of stresses. A procedure for applying the model to identify stress tensors that are most likely to promote a desired reaction is illustrated. The results also indicate that this procedure provides insight into the connection between the form of a stress tensor and the changes in energy occurring during a stress-induced solid state transformation.
固态变换在许多科学技术领域都很重要。在此,一个模型用于预测稳态点的相对能量沿反应路径应力诱导的固体转化进行了评估和应用。该模型基于系统能量相对于单元胞的变化的二阶展开,并且需要少量的参数,这些参数可以通过量子化学计算获得。该模型与量子化学计算结果的比较表明,该模型在合理的应力范围内准确地再现了应力诱导转化过程中能量的变化。说明了应用该模型识别最可能促进期望反应的应力张量的程序。结果还表明,这一过程提供了对应力张量的形式与应力诱导的固态转变过程中能量变化之间的联系的见解。
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引用次数: 0
Award Lecture Paper: Nickel-Catalyzed N-Arylation of Optically Pure Amino Acid Esters with Activated (Hetero)aryl Electrophiles 获奖演讲论文:镍催化光学纯氨基酸酯与活化的(杂)芳基亲电试剂的n -芳基化
IF 1.1 4区 化学 Q3 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2023-02-02 DOI: 10.1139/cjc-2022-0290
Travis Lundrigan, Joseph P. Tassone, M. Stradiotto
An efficient method for the C–N cross-coupling of (hetero)aryl (pseudo)halides with optically pure α-amino acid esters employing a commercially available nickel catalyst and weak inorganic base was developed. This is the first example of Ni-catalyzed N-arylation of amino acid esters without the use of electrochemistry, which was shown to effectively couple a variety of amino acid tert-butyl esters with (hetero)aryl chlorides, bromides, and tosylates in high yields and excellent enantioretention. Base-mediated racemization was revealed during control experiments, but increasing the steric bulk of the amino acid ester group limited the amount of racemization of the product.
建立了一种利用市售镍催化剂和弱无机碱催化(杂)芳基(伪)卤化物与光学纯α-氨基酸酯进行C-N交联反应的有效方法。这是第一个不使用电化学的镍催化氨基酸酯n -芳基化的例子,该方法被证明可以有效地将各种氨基酸叔丁基酯与(杂)芳酰氯、溴化物和甲酰酸盐偶联,收率高,对映保持性好。在对照实验中发现了碱基介导的外消旋,但增加氨基酸酯基的空间体积限制了产物的外消旋量。
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引用次数: 0
Note of appreciation 感谢信
4区 化学 Q3 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2023-02-01 DOI: 10.1139/cjc-2023-0007
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引用次数: 0
Thermal and electrical transport conductivities of novel ordered double two-dimensional MXenes via density functional theory 基于密度泛函理论的新型有序双二维MXenes的热导率和电导率
IF 1.1 4区 化学 Q3 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2023-01-19 DOI: 10.1139/cjc-2022-0070
Ekwevugbe Omugbe, O. Osafile, O. Nenuwe, E. Enaibe, E. E. Elemike
In this paper, we examined the effects of transition metal replacement and ordering in 2D M3C2O2 MXene on the electronic structure, thermal and electrical conductivities using the density functional theory and also the Boltzmann transport theory within the constant relaxation time approximation. We derived the following oxygen functionalized ordered double metal MXenes Ti2YC2O2, Y2TiC2O2 Sc2YC2O2, and Y2ScC2O2 through the surface and sub-layer tuning. The results revealed that the ordered MXenes give rise to different electronic structure and transport properties. The electronic thermal conductivities obtained in terms of the relaxation time increase with increase in absolute temperature, while the electrical conductivities decrease with increase in temperature. The respective transport properties of Y2TiC2O2 and Sc2YC2O2were found to be enhanced due to the increased squared band velocity, density of state and low Seebeck coefficient compared to Ti2YC2O2 and Y2ScC2O2 MXenes. Generally, the MXene materials investigated in this work were found to possess metallic properties with the existence of energy overlap around the Fermi level. The computed formation energies support chemical stability in all the materials.
本文利用密度泛函理论和恒定弛豫时间近似下的玻尔兹曼输运理论,研究了二维M3C2O2 MXene中过渡金属置换和有序对其电子结构、导热性和电导率的影响。我们通过表面和亚层调谐得到了以下氧功能化有序双金属MXenes Ti2YC2O2, Y2TiC2O2, Sc2YC2O2和Y2ScC2O2。结果表明,有序的MXenes产生了不同的电子结构和输运性质。根据弛豫时间计算得到的电子导热系数随绝对温度的升高而增大,而电导率随温度的升高而减小。与Ti2YC2O2和Y2ScC2O2 MXenes相比,Y2TiC2O2和sc2yc2o2各自的输运性能都得到了增强,这是因为它们的平方带速度、态密度和塞贝克系数都有所提高。一般来说,在这项工作中研究的MXene材料被发现具有金属性质,并且在费米能级周围存在能量重叠。计算得到的形成能支持所有材料的化学稳定性。
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引用次数: 1
Synthesis and thermal stability of a novel polyfunctional pyridine-based derivative featuring amino, nitro, and guanidine groups 一种新型氨基、硝基和胍基多官能团吡啶衍生物的合成和热稳定性
IF 1.1 4区 化学 Q3 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2023-01-17 DOI: 10.1139/cjc-2022-0057
Xu-Qing Liu, Lina Hao, Renfa Zhang, Congming Ma, P. Ma
A new pyridine derivative 1-(4-amino-3,5-dinitropyridin-2-yl) guanidine (ADG) was synthesized through nitration and substitution reaction using 4-amino-2-cholopyridine as raw material. Its structure was characterized by spectroscopy, nuclear magnetic resonance, and mass spectrometry. The crystal of ADG is monoclinic, space group Pbca with crystal parameters of a = 7.23 Å, b = 14.56 Å, c = 17.93 Å, α = β= γ= 90 Å, V = 1911 Å3, μ = 0.143 mm−1, and Z = 8. This new molecule exhibits moderate density ( ρ= 1.677 g cm−3), good thermal stability with a decomposition temperature of 217 °C, and moderate detonation property with detonation pressure of 20.83 GPa and detonation velocity of 7.00 km s−1. The Hirshfeld surface analysis revealed a significant contribution of weak interactions to the packing forces for molecules. Electron localization function analysis indicates that there is substantial electron localization in regions of C–H, N–H, and N–O covalent bond sites.
以4-氨基-2-胆吡啶为原料,经硝化取代反应合成了一种新的吡啶衍生物1-(4-氨基-3,5-二硝基吡啶-2-基)胍(ADG)。用光谱学、核磁共振和质谱法对其结构进行了表征。ADG晶体为单斜晶,空间群Pbca,晶体参数为a = 7.23 Å, b = 14.56 Å, c = 17.93 Å, α = β= γ= 90 Å, V = 1911 Å3, μ = 0.143 mm−1,Z = 8。该分子具有中等密度(ρ= 1.677 g cm−3)、良好的热稳定性(分解温度为217℃)和中等爆轰性能(爆轰压力为20.83 GPa,爆轰速度为7.00 km s−1)。Hirshfeld表面分析揭示了弱相互作用对分子堆积力的重要贡献。电子定位函数分析表明,在C-H、N-H和N-O共价键位点存在大量的电子定位。
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引用次数: 1
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Canadian Journal of Chemistry
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