CH_3CN+CH_3→CH_2CN+CH_4氢消除反应的直接动力学研究

采用直接动力学方法,对乙腈与甲基的反应进行了理论研究.在BHandHLYP/6-311G(d,p)和MP2/6-311G(d,p)水平下获得,稳定点的几何结构、振动频率及最小能量路径(MEP),在G3(MP2)和MC-QCISD水平下对能量信息进一步确认.利用正则变分过渡态理论,结合小曲率隧道效应校正(CVT/SCT)方法计算了该反应在220K～2000K的速率常数,与实验值符合得很好.     

Quantum superchemistry of de Broglie waves: New wonderland at ultracold temperature

The experimental realization of atomic Bose-Einstein condensation at ultracold temperature has led to rapid advances in creating and manipulating cold molecules, and which has given birth to a new research field of quantum matter-wave superchemistry. Contrary to the classical Arrhenius law, the tunneling-dominated ultracold reactions can be realized through the highly-controlled magneto-optical technique. Novel quantum effects have been identified in these cold reactions, such as the super-selectivity rule in dissociating triatomic molecules, and the quantum size (vessel-shape) effect. In this review, we focus on a variety of new achievements in this fascinating matter-wave wonderland, including the quantum finite-number effect and double-slit interference in assembling cold molecules, the quantum noise in triggering collective abstraction reaction, and the magnetic phase transition in a laser-catalyzed quantum spin-mixing gas. The practical applications of matter-wave superchemistry are also introduced, such as the optical information storage via quantum photo-association, and the laser-enhanced creation of spinor or even chiral molecules.     

Reflective abstraction in computational thinking

Computational thinking has become an increasingly popular notion in K-12 and college level education. Although researchers have accepted that abstraction is a central concept in computational thinking, they are quick to disagree on the meaning of it. A focus on reflective abstraction has led to the development of APOS Theory in Mathematics education. This has resulted in many cases of improved student learning in Mathematics (Arnon et al., 2013). Our main aim in this paper is to construct a theoretical bridge between computational thinking and APOS Theory and show that reflective abstraction can be used in the context of computational thinking.     

Effect of Lewis acids and low temperature initiators on the allyl transfer reaction involving phthalimido-N-oxyl radical

Previously, we reported allyl transfer reactions of allyl bromide and allyl phthalimido-N-oxyl substrates with hydrocarbons that result in CC bond formation. In both cases, efficient chain transfer processes along with high reaction yields were observed. Since PINO chemistry leads to an environmentally friendly method of hydrocarbon functionalization, additional studies were performed in order to improve the process. To expand the utility of this reaction, we carried out experiments to optimize reaction conditions and tested the effect of Lewis acids and low temperature initiators. Although allyl-PINO substrates reacted slightly slower than the bromides, the reactions were cleaner with little or no side products. The chain lengths for these reactions were compromised at lower temperatures, attributable to the high activation energy required for the hydrogen atom abstraction by PINO. The addition of a Lewis acid catalyst (AlCl₃) improves the product yield and reaction rate, possibly due to the formation of a PINO/AlCl₃ complex which lowers the activation energy for hydrogen abstraction step.     

Kinetic Modeling of Hydrogen Abstractions Involving Sulfur Radicals

One of the requisites for the development of detailed reaction networks is the availability of accurate kinetic data. Group additivity based models linking the Arrhenius parameters to structural characteristics of the transition state have proven to be a valuable tool to obtain those data. In this work, group additivity values are presented to allow a broad range of C H and S H hydrogen abstraction reactions by S radicals to be modeled. Rate coefficients in the temperature range from 300 to 1500 K are obtained by using the CBS-QB3 method in the high-pressure limit and are corrected for tunneling and anharmonicity of rotation about the transitional bond. A total of 149 reactions are studied. From these reactions, a total of 52 group additivity values and 35 resonance corrections are derived. The general applicability of the group additivity method is demonstrated for a test set containing 25 reactions. At 300 K, rate coefficients are on average reproduced within a factor of 2.8. The mean absolute deviations on the Arrhenius parameters are 2 kJ mol⁻¹ for the activation energy and 0.38 for log A in which A is the pre-exponential factor.     

1-乙酰基-2,3-吲哚二酮的光诱导氢转移反应的CIDNP研究

采用CIDNP方法对UV光照条件下的1-乙酰基-2, 3-吲哚二酮与几类氢给体的光诱导氢转移反应进行了研究.     

浅谈在高等数学教学中如何将基本概念形象化

高等数学中的基本概念具有高度抽象性，是教师讲授的难点，也是学生学习的重点，而基本概念的掌握是学生学习理解高等数学的关键，也是培养学生学习兴趣的前提．本总结了多种方法，将基本概念形象化变为可“听”，可“看”，可“摸”，降低了基本概念的教与学难度，提高了学生学好高等数学的兴趣。     

Positional and compositional disorder in a ruthenium(II) piano‐stool complex

In (η⁶‐p‐cymene)(difluorophosphinato‐κO){2‐[(1H‐pyrazol‐1‐yl)methyl‐κN²]pyridine‐κN}ruthenium(II) 0.85‐hexafluorophosphate 0.15‐tetrafluoroborate, [Ru(PO₂F₂)(C₁₀H₁₄)(C₉H₉N₃)](PF₆)_0.85(BF₄)_0.15, (I), the [PO₂F₂]⁻ ligand exhibits positional disorder due to one F atom and one O atom sharing the same two positions related by a mirror reflection across the O—P—F plane. The correct composition of this coordinated anion was successfully determined to be [PO₂F₂]⁻ by refining the complex with various tetrahedral anions in which terminal atoms have similar atomic form factors. The noncoordinated counter‐ion is compositionally disordered between [PF₆]⁻ and [BF₄]⁻. The difficulty in determining the correct composition of this anion illustrates the importance of a crystallographer remaining impartial and open to encountering unexpected moieties in the process of elucidating a structure.     

Poly(vinyl alcohol)–Thioxanthone as One‐Component Type II Photoinitiator for Free Radical Polymerization in Organic and Aqueous Media

A novel one‐component type II polymeric photoinitiator, poly(vinyl alcohol)–thioxanthone (PVA–TX), is synthesized by a simple acetalization process and characterized. PVA–TX enables photopolymerization of methyl methacrylate and acrylamide in both organic and aqueous media. Photopolymerization proceeds even in the absence of a co‐initiator since PVA–TX possesses both chromophoric and hydrogen donating sites in the structure.

     

Emergence of a New [NNN] Pincer Ligand via Si−H Bond Activation and β-Hydride Abstraction at Tetravalent Cerium

The cerium(IV) pyrazolate complexes [Ce(Me₂pz)₄]₂ and [Ce(Me₂pz)₄(thf)] initiate β-hydride abstraction of the bis(dimethylsilyl)amido moiety, to afford a heteroleptic cerium(IV) species containing a dimethylpyrazolyl-substituted silylamido ligand, namely [Ce(Me₂pz)₃(bpsa)] (bpsa=bis((3,5-dimethylpyrazol-1-yl)dimethylsilyl)amido; Me₂pz =3,5-dimethylpyrazolato), along with some cerium(III) species. Remarkably, the nucleophilic attack of the pyrazolyl at the silicon atom and concomitant Si−H-bond cleavage is restricted to the tetravalent cerium oxidation state and appears to proceed via the formation of a transient cerium(IV) hydride, which engages in immediate redox chemistry. When [Ce(Me₂pz)₄]₂ is treated with [Li{N(SiMe₃)₂}], that is, in the absence of the SiH functionality, any redox chemistry did not occur. Instead, the ceric ate complex [LiCe₂(Me₂pz)₉] and the stable mixed-ligand ceric species [Ce(Me₂pz)₂{N(SiMe₃)₂}₂] were obtained.