化学能转化成电能的实验设计

以常见的铜锌原电池反应为例,设计了一组对比实验装置,即化学反应装置与原电池装置。以化学反应装置中的能量变化为依据,展示了化学反应中释放出的能量具体形式为“热”与“功”;通过与原电池装置的比较,证明原电池实验装置中的“热”转化为了电能。     

String model of chemical reaction coordinate

A geometrical model for estimating the effects of external fields upon a reaction path is proposed. The reaction path is defined as the intrinsic reaction coordinate (IRC) which is treated as a string. The IRC frame is introduced in order to uniquely determine the attitude of the string with respect to the reaction medium. The string is thrown in the external fields of the reaction medium, and slides or rotates, and is deformed. The cell structure attached to the string is also deformed. A perturbational approach to the reaction rate formula is presented.     

Determination of the Kinetic Significance of Elementary Steps in the Reaction of Ethylbenzene Oxidation Inhibited by Ionol

The kinetic significance of elementary steps in the liquid-phase reaction of ethylbenzene oxidation inhibited by ionol (2,6-di-tert-butyl-4-methylphenol) was determined with the use of the value method. The nature of the effectiveness of ionol from the class of ortho-substituted phenols was considered. It consists in a ponderable role of the reaction of chain carriers (peroxy radicals) with the inhibitor with a decrease in the contribution of the reverse reaction. In this case, the relatively weak participation of the antioxidant at the step of degenerate chain branching and the high reaction rate constant of the interaction of phenoxy radicals with each other are of considerable importance. The value ranking of steps allowed us to diminish them; this simplified the reaction mechanism under various initial conditions. A satisfactory agreement between base reaction mechanisms, which describe experimental results and the behavior of the inhibited reaction under new reaction conditions, is considered as a reliability criterion for the prediction made.     

Direct dynamics trajectory study of vibrational effects: can polanyi rules be generalized to a polyatomic system?

We present an ab initio direct dynamics trajectory study of the hydrogen abstraction reaction: H2CO+ + CD4 --> H2COD+ + CD3, with methane excited in two different distortion modes (nu4 and nu2). The trajectory simulations were able to reproduce experimental results and for the first time show how vibrational enhancement originates in reaction of small polyatomic species. Roughly equal contributions from two vibrational enhancement mechanisms were found. The "distortion" mechanism correlates the vibrational effects with vibration-induced reactant distortions, and the "velocity" mechanism correlates vibrational effects with vibrational velocities of the constituent atoms. This reaction has a reactant-like transition state and, thus, would correspond to an "early" barrier system in the context of the well-known Polanyi rules for predicting effects of vibration and collision energy. Straightforward application of these rules would predict that vibration should be ineffective in driving reaction, in disagreement with both experiment and trajectory results. Using the trajectories for guidance, we were able to construct a two-dimensional cut through the reaction potential energy surface that does suggest a predictive, Polanyi-type rule.     

Time-variable Method for Studying Reaction Rates in a Calorimeter

A novel method for the determination of rate constants of reactions, the time-variable method, is proposed in this paper. The method needs only three time points (t), peak heights () and pre-peak areas (), obtained from the measured thermoanalytical curve. It does not require the thermokinetic reaction to be completed. It utilizes data-processing on a computer to give the rate constants. Four reaction systems, including a first-order reaction, second-order reactions (with equal concentrations and with unequal concentrations) and a third-order reaction, were studied with this method. The method was validated and its theoretical basis was verified by the experimental results.This revised version was published online in November 2005 with corrections to the Cover Date.     

Phase space geometry of dynamics passing through saddle coupled with spatial rotation

Nonlinear reaction dynamics through a rank-one saddle is investigated for many-particle system with spatial rotation. Based on the recently developed theories of the phase space geometry in the saddle region, we present a theoretical framework to incorporate the spatial rotation which is dynamically coupled with the internal vibrational motions through centrifugal and Coriolis interactions. As an illustrative simple example, we apply it to isomerization reaction of HCN with some nonzero total angular momenta. It is found that no-return transition state (TS) and a set of impenetrable reaction boundaries to separate the "past" and "future" of trajectories can be identified analytically under rovibrational couplings. The three components of the angular momentum are found to have distinct effects on the migration of the "anchor" of the TS and the reaction boundaries through rovibrational couplings and anharmonicities in vibrational degrees of freedom. This method provides new insights in understanding the origin of a wide class of reactions with nonzero angular momentum.     

Synthesis and some chemical transformations of N-(2,4-dichloro-s-triazin-6-yl)-N-alkyl-N′-alkylchloroformamidines

The reaction of cyanuric acid chloride (2,4,6-trichloro-1,3,5-triazine) with a number of dialkylcarbodiimides was investigated. It is shown that the corresponding N-(2,4-dichloro-s-triazin-6-yl)-N-alkyl-N-alkylchloroformamidines are formed as a result of the reaction. The reaction of the synthesized chloroformamidines with primary and secondary amines was investigated. It is shown that the reaction takes place with substitution of the chlorine atom in the triazine ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 121–123, January, 1982.     

The Diels-Alder reaction of C60 and cyclopentadiene in mesoporous silica as a reaction medium

As a new organic reaction medium, a periodic mesoporous inorganic material was found to function as a "solid solvent" in a Diels-Alder reaction of C(60) with cyclopentadiene. This finding was supported by a concentration effect and a kinetic study of the reaction.     

Solid-Phase Synthesis of Calcium Carbide in a Plasma Reactor

A laboratory-scale spout-fluid bed reactor with a dc plasma torch was used to study the solid-phase synthesis of calcium carbide. Calcium oxide powder with a mean particle size of 170 m was reacted with graphite powder (130 m). Argon was used to initiate the plasma and hydrogen gas was then added to increase power and raise the plasma jet enthalpy. Experimental results showed that the reaction took place in the vicinity of the plasma jet and that conversion to calcium carbide increased linearly with reaction time. The rate of conversion increased exponentially with plasma jet temperature, indicating that chemical reaction was the controlling mechanism. Microscopic analysis of the solid product showed that calcium carbide was formed around both reactants, and that the reaction followed a shrinking core model. Although melting and agglomeration of partially reacted particles occurred at high temperature, resulting in instability of the bed and impeding the reaction progress, high conversions are expected in a continuous process with optimized reactor design.     

Determination of the reactive surface area of silica

Summary The surface area available for reaction in silylation reactions has been determined by reaction of the silica with a radioactively labelled alkyldimethylchlorosilane followed by liquid scintillation counting of either a solid or a dissolved silica sample. The results are compared with values obtained by nitrogen adsorption and the pore size distributions of the products before and after reaction.Presented at the 14th International Symposium on Chromatography London, September, 1982     

Grignard reaction with 2, 6-dialkoxydihydro- and -tetrahydropyrans

The Grignard reaction with 2, 6-dialkoxytetrahydropyran and 2, 6-dialkoxy-5, 6-dihydro-2H-pyran has been studied. In both cases the reaction takes place with the opening of the pyran ring and the formation of alkoxy-substituted saturated or , -unsaturated alcohols.During the complption of our work, a paper appeared in which the Grignard reaction with 2, 6-diethoxytetrahydropyran was studied [1].     

Glycosidation with a disarmed glycosyl iodide: promotion and scope

[reaction: see text] Glucuronyl iodide 1 has been studied in detail as a "disarmed" glycosyl donor. In a model reaction, using N-iodosuccinimide (NIS) as a promoter and 2-phenylethanol as acceptor, best results were obtained using NIS with I(2), followed by trimethylsilyltrifluoromethanesulfonate (TMSOTf). When a series of primary and secondary alcohols was glycosylated using these conditions, yields of 60-83% of beta-glucuronides were obtained. Various "nonheavy" metal salts also effectively catalyzed the model reaction but led to significant amounts of alpha-product with less reactive secondary alcohols.     

Mechanism and activity of ruthenium olefin metathesis catalysts: the role of ligands and substrates from a theoretical perspective

The reaction mechanism of olefin metathesis by ruthenium carbene catalysts is studied by gradient-corrected density functional calculations (BP86). Alternative reaction mechanisms for the reaction of the "first-generation" Grubbs-type catalyst (PCy(3))(2)Cl(2)Ru=CH(2) (1) for the reaction with ethylene are studied. The most likely dissociative mechanism with trans olefin coordination is investigated for the metathesis reaction between the "first-" and the "second-generation" Grubbs-type catalysts 1 and (H(2)IMes)(PCy(3))Cl(2)Ru=CH(2) (2) with different substrates, ethylene, ethyl vinyl ether, and norbornene, and a profound influence of the substrate is found. In contrast to the degenerate reaction with ethylene, the reactions with ethyl vinyl ether and norbornene are strongly exergonic by 8-15 kcal/mol, and this excess energy is released after passing through the metallacyclobutane structure. While the metallacyclobutane is in a deep potential minimum for degenerate metathesis reactions, the energy barrier for the [2+2] cycloreversion vanishes for the most exergonic reactions. On the free energy surface under typical experimental conditions, the rate-limiting steps for the overall reactions are then either metallacyclobutane formation for 1 or phosphane ligand dissociation for 2.     

An unexpected highly diastereoselective double Baylis-Hillman reaction of per- (or poly)fluorophenyl aromatic aldimines with methyl vinyl ketone

Aza-Baylis-Hillman reaction of per- (or poly)fluorophenyl aromatic aldimines 1 with methyl vinyl ketone (MVK) was studied. It was found that both the used Lewis base and solvent can significantly affect the reaction. Using triphenylphosphine as a Lewis base, the reaction of 1 with MVK proceeded smoothly to give the normal Baylis-Hillman adduct 2 along with the double Baylis-Hillman adduct 3 as by-product in THF. When 1,4-diazabicyclo[2.2.2]octane was used as a Lewis base in DMF, the aza-Baylis-Hillman reaction of 1 with MVK gave the double aza-Baylis-Hillman adduct 3 exclusively in moderate to good yields with excellent diastereoselectivities. The double Baylis-Hillman adduct 3 was conveniently converted to fluorine-containing 4-alkylidene-2-cyclohexen-1-ones under mild reaction conditions in good yields.     

煤氧化增重现象中的控制反应及其动力学解析

以热重实验中的煤氧化增重现象为线索, 对400 ℃前煤氧化的反应机理和动力学过程进行了理论研究. 借助于平行反应理论, 将煤低中温氧化过程简化为3 个平行的竞争反应, 包括水分析出、氧吸附和固相氧化产物分解的反应以及直接的“burn-off”反应. 通过对不同氧体积浓度(10%, 21%和40%)下的实验数据全过程上的非线性最小二乘法拟合, 确定出各反应的动力学参数以及相应的温度作用范围. 模化的结果与实验数据高度贴近, 证明了反应模型和计算方法的可靠性. 煤低中温氧化过程中的质量变化, 主要是由氧吸附反应和固相氧化产物的分解反应所控制的; 由直接的“burn-off”反应所引起的质量变化则相对较小. 煤氧化增重现象对应的反应及动力学过程并不能由单一反应模型来近似. 氧浓度的提高导致氧吸附反应和固相氧化产物的分解反应加剧, 而“burn-off”反应受氧浓度的影响并不显著, 这是由用于解析动力学参数而选定的实验数据的温度范围和特征所决定的.     

均相催化的醇和胺借氢反应

醇和胺的借氢反应是一种制备胺类化合物的绿色途径。本文介绍了借氢反应的概念,并重点介绍了均相催化的醇和胺之间借氢反应的起源、重要进展以及未来的发展趋势。     

Acid–Base Behavior in Supercritical Water: β-Naphthoic Acid–Ammonia Equilibrium

Equilibrium constants for the reaction of -naphthoic acid and ammonia, K _BHA, were measured with UV-vis spectroscopy in water from 25°C to 400°C. At high density K _BHA decreases with temperature, the normal behavior for an exothermic reaction of a stronger acid and base to a weaker acid and base. At low density, the reaction becomes endothermic as the solvation of the ionic products becomes weaker. These data were combined with literature results for the dissociation of water and ammonia to determine equilibrium constants for the dissociation of -naphthoic acid and the reaction of -naphthoic acid and OH^- Whereas the density (and dielectric constant) of water have only a modest effect on the isocoulombic reaction of -naphthoic acid and OH^-, they have a large effect on all of the other reactions which are ionogenic.     

Ab initio study of catalyzed and uncatalyzed amide bond formation as a model for peptide bond formation: Ammonia-Glycine reactions

As a model reaction for peptide and bond formation, the S_N2 reactions between glycine and ammonia have been studied with and without amine catalysis: using ab initio molecular-orbital methods. For each of the catalyzed and uncatalyzed reactions, two reaction mechanisms have been examined: a two-step and a concerted mechanism. The stationary points of each reaction, including intermediate and transition states, have been identified and free energies calculated for all geometry-optimized reaction species to determine the thermodynamics and kinetics of the reaction. The calculations demonstrate that a second ammonia molecule catalyzes amide bond formation, and that the two-step mechanism is more favorable than the concerted one for the catalyzed reaction, while for the uncatalyzed reaction both mechanisms are competitive.     

SULFATION OF PACHYMAN WITH CHLOROSULFONIC ACID USING THE IMPROVED WOLFROM METHOD

High purity polysaccharide of pachyman was isolated from the powder of Poria cocos sclerotium with an yield of 77.8%. The intrinsic viscosity of polysaccharide was found to be 78.95 mL/g in DMSO solution at 25℃. The isolated polysaccharide was reacted with chlorosulfonic acid to obtain pachyman sulfate using the improved Wolfrom method. The results of the orthogonality experiment on the sulfation reaction identified that the effectiveness of the reaction conditions on the degree of sulfation and the value of intrinsic viscosity is in the following order: molar ratio of chlorosulfonic acid to glucoside (3-5) ＞ reaction temperature (60-80℃) ＞ reaction time (1-2 h). The kinetic studies of the pachyman sulfationindicated that the hydrolysis is accompanied with the sulfation process. The decrease in intrinsic viscosity of the sulfated pachyman is proportional to the increase in the degree of sulfation under the mild reaction conditions of ＜ 80℃,chlorosulfonic acid/glucoside mole ratio ＜ 5, and reaction time ＜ 2 h. Beyond the above reaction conditions, excessive loss of -OH group occurs during hydrolysis. The NMR results indicated a complete sulfation on C-6 and a partial sulfation on the C-2 and C-4 of glucoside.     

Graphene layer growth chemistry: five- and six-member ring flip reaction

Reaction pathways are presented for hydrogen-mediated isomerization of a five- and six-member carbon ring complex on the zigzag edge of a graphene layer. A new reaction sequence that reverses the orientation of the ring complex, or "flips" it, was identified. Competition between the flip reaction and the "ring separation" was examined. Ring separation is the reverse of the five- and six-member ring complex formation reaction, previously reported as "ring collision". The elementary steps of the pathways were analyzed using density functional theory (DFT). Rate coefficients were obtained by solution of the energy master equation and classical transition-state-theory utilizing the DFT energies, frequencies, and geometries. The results indicate that the flip reaction pathway dominates the separation reaction and should be competitive with other pathways important to the graphene zigzag edge growth in high-temperature environments.