Transients in the vibrational excitation of cyclobutane decomposition using the variable encounter method

The probability of reaction of cyclobutane molecules in a fixed time interval after experiencing a known variable number of collisions with a hot surface at temperatures between 749 K and 1126 K has been determined using the Variable Encounter Method. Calculations utilizing exponential or gaussian models for energy transfer enable the average amounts of energy transferred for deactivating collisions, <ΔE′?, to be estimated. The exponential model fits the experimental data the best and, using this model, <ΔE′? is 2430 cm^?1 at 749 K and decreases to 1470 cm^?1 at 1126 K. Incubation times are derived from the mean first passage times.     

Vibrational analysis of 1-iodopropane, 1-iodobutane and 1,3-diiodopropane

Normal coordinate calculations were made for the trans and gauche conformations of n-propyl and n-butyl iodides and for the tt, tg and gg conformations of 1,3-diiodopropane. Nineteen force constants of a 48-parameter modified valence force field were adjusted to provide the best fit for 114 frequencies (excluding C-H) of all these conformations except for gg, 1,3-di-iodopropane. The average difference between observed and calculated wavenumbers was 6.6 cm^?. Previous vibrational assignments were revised.     

Intermolecular energy transfer in two-channel unimolecular reactions: the pyrolysis of 1-iodopropane

Pressure-dependent unimolecular reaction rate coefficients have been obtained for the two channels of decomposition of 1-iodopropane (dilute in Ne), using very low-pressure pyrolysis (VLPP). The interpretation, taking finite diffusion rates into account, gives convincing evidence for “weak” gas/gas collisions and “strong” gas/wall collisions.     

Collisional relaxation of transient vibrational energy distributions in a thermal unimolecular system. The variable encounter method

A method has been developed, called the Variable Encounter Method, for the study of the relaxation of an initial vibrationally cold ensemble of molecules into a vibrationally hot distribution by a known and variable number of successive collisions with a hot wall. The theory of the experiment is presented. The system studied was the isomerization of 1,1-cyclopropane-d₂ with a fused quartz wall temperature of 800 K to 1175 K, and average number of collisions from 2.3 to 22.3. Various modified gaussian and exponential models of energy transfer were found to give agreement with the data. The average down-step size was found to decline from ≤ 3500 cm^?1 at the lowest temperature to ≈ 2500 cm^? at the highest on the basis of a gaussian model. A mathematical analysis of the relation between mean first passage times and incubation times is given. Incubation times increase from ≈ 7 to ≈ 12 collisions with increasing temperature. Transient population distributions and the sequential reaction probabilities as a function of collision number are calculated.     

SCFMO calculation of the 1∶1 charge-transfer complex between benzene and p-benzoquinone by the variable integrals method II

The charge-transfer complex system between benzene and p-benzoquinone is treated as a single conjugated system of -electrons and its electron states are calculated by the Variable Integrals Method II. For three models of the charge-transfer complex, potential energy curves, stabilization energies, orbital energy diagrams, electron densities, bond orders, dipole moment and electronic transition energies are discussed. The agreement between theory and experiment is satisfactory as for as the electronic spectra are concerned.

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Zusammenfassung Der Ladungsübertragungs-Komplex zwischen Benzol und p-Benzochinon wird als ein einziges konjugiertes -Elektronensystem behandelt. Seine -Elektronenzustände werden nach der Methode II der Variablen Integrale berechnet. Für drei Modelle des Komplexes werden die Potentialkurven, die Stabilisierungsenergien, die Diagramme der Orbitalenergien, die Elektronendichten, die Bindungsordnungen, die Dipolmomente sowie die elektronischen Übergangsenergien untersucht. Die Übereinstimmung mit dem Experiment ist für die Elektronenspektren zufriedenstellend.

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Résumé Calcul des états électroniques par la méthode des intégrales variables II pour le complexe de transfert de charge entre le benzène et la p-benzoquinone considéré comme un système conjugé unique. Discussion de trois modèles de complexe de transfert de charge: courbes d'énergie potentielle, énergies de stabilisation, diagrammes d'énergie orbitale, densités électroniques, moment dipolaire et énergies de transition électronique. L'accord entre théorie et expérience est satisfaisant tout au moins pour les spectres électroniques.

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Presented at the 2nd Symposium on Structural Organic Chemistry, Osaka, November, 1969.     

F原子与i-C3H7I反应的动力学研究

本文利用交叉分子束技术和激光诱导萤光方法, 研究了F+i-C3H7I→IF+i-C3H7反应的动力学过程. 获得了产物IF相对初生振动分布和相对细致反应速率常数. 初生态布居接近于模型III下的统计理论斯待值, 这不仅表明反应经过长寿命“配合物", 而且也说明自由基i-C3H7的内态是激发的. 另外, 确定了反应的产物IF内部能量分配和总反应截面σ, σ=(3.6±0.5)×10^-^1^6cm^2.     

Thermodynamic Investigation on the Pyrolysis of 1-Hexene

<正>The pyrolysis of 1-hexene can act as a prototype of pyrolytic mechanism in petroleum processing. Details of C-C bond cleavage in the 1-hexene pyrolysis were investigated at the MP2/6-311++G~(**) basis set level. The equilibrium geometries and key thermodynamic parameters such as Gibbs free energies and thermal enthalpies were gained. Our theoretical results show that the entropy effect plays a significant role in dissociative processes. The dissociation of 1-hexene-4-yl radical into C_4H_6 and C_2H_5 is not an elementary reaction, but a process involving H-transfer and C-C rupture.     

Pyrolysis of 1-phenyl-3-pyrazolidinone

Pyrolysis of 1-phenyl-3-pyrazolidinone (phenidone) was examined in static air atmosphere by the conventional dynamic heating technique in a derivatograph. The thermal stability of 1-phenyl-3-pyrazolidinone, its melting point and the kinetic parametersE, A andn of the first partial process of the pyrolysis at different heating rates were determined. It is shown that the thermal decomposition of 1-phenyl-3-pyrazolidinone in the presence of oxygen is a rather complicated process composed of several overlapping reactions. The pyrolysis is influenced by the conditions of thermal analysis.

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Zusammenfassung Die Pyrolyse von 1-Phenyl-3-pyrazolidinon (Phenidon) wurde mit einem Derivatographen in einer statischen LuftatmosphÄre und bei konventioneller dynamischer Aufheizung untersucht. Die thermische StabilitÄt und der Schmelzpunkt von 1-Phenyl-3-pyrazolidinon sowie die kinetischen ParameterE, A undn des ersten Teilprozesses der Pyrolyse für verschiedene Aufheizgeschwindigkeiten wurden bestimmt. Es stellte sich heraus, da\ die in Gegenwert von Sauerstoff verlaufende thermische Zersetzung von 1-Phenyl-3-pyrazolidinon ein ziemlich komplizierter, aus mehreren sich überlappenden Teilschritten bestehender Proze\ ist. Die Pyrolyse wird durch die Bedingungen der thermischen Analyse beeinflu\t.

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1--3 () . , E, A n , . , 1--3- , . .

     

裂解气相色谱法分析铸造用聚苯乙烯泡沫塑料热解产物

采用裂解气相色谱法研究了汽化模铸造工艺用聚苯乙烯泡沫塑料在４５０～１０００℃温度范围内热分解产物的分布,定量测定了４种主要蒸气态热分解产物的含量。结果表明,所采用的分析方法对研究铸造用高分子材料热分解产物行之有效,而且方法简单、快速、准确。     

Pyrolysis of propane in the presence of14C2H4 studied by the kinetic isotope method

The kinetic isotope method was used to explain the role of ethylene in the pyrolysis of propane. The mechanism of the radioactivity appearance in methane and propylene is proposed.     

Pyrolysis kinetics and combustion of thin wood by an advanced cone calorimetry test method

Pyrolysis kinetics analysis of extractives, holocellulose, and lignin in the solid redwood over the entire heating regime was possible by specialized cone calorimeter test and new mathematical analysis tools. Added hardware components include: modified sample holder for the thin specimen with tiny thermocouples, the methane ring burner with stainless-steel mesh above cone heater, and the water vapor sensor in heated gas sampling lines. Specialized numerical deconvolutions were applied to the oxygen and water vapor analyzer signals to synchronize with the rapid-responding CO/CO₂ analyzer signals. From this data, the mass flow rates of carbon, hydrogen, and oxygen within the wood volatiles as function of time were obtained, which allowed deducing the mass flow rate of significant molecules of wood volatiles that have their origins in the wood constituents of extractives, holocellulose, and lignin. Accurate analytical solution of pyrolysis kinetics of appropriate competitive reactions that continuously conserved carbon, hydrogen, and oxygen mass flow rates was obtained for piecewise exponentially-shaped, spatially uniform temperature within the specimen as implemented conveniently in MS Excel spreadsheet.     

高温热解法制备硒化镉纳米晶

以脂肪酸和三辛基氧化膦为表面活性剂,采用高温热解硒与镉的前聚体,制备出分散性好的CdSe纳米晶.吸收光谱和荧光光谱研究表明,控制反应时间可以改变CdSe纳米晶的荧光强度.     

1-己烯热裂解基元反应选择性分析

1-己烯在873～973 K温度区间热裂解转化反应经历自由基链式反应机理, 主要产物包括C₁~C₃烷烃、C₂~C₄烯烃、丁二烯、环戊烷、环戊烯、焦炭和氢气. 各种产物的生成涉及不同的基元反应途径, 并具有不同的基元反应或然率(Reaction path probability, RPP). 提高反应温度有利于反应物分子的热均裂(链引发)和焦炭生成反应. 随着反应温度从873 K提高到973 K, 标志链式反应特征的动力学链长(KCL)从5.86缩短为5.19.     

Rates and mechanisms for the reactions of chlorine atoms with iodoethane and 2-iodopropane

The reaction of Cl atoms with iodoethane has been studied via a combination of laser flash photolysis/resonance fluorescence (LFP-RF), environmental chamber/Fourier transform (FT)IR, and quantum chemical techniques. Above 330 K, the flash photolysis data indicate that the reaction proceeds predominantly via hydrogen abstraction. The following Arrhenius expressions (in units of cm3 molecule(-1) s(-1)) apply over the temperature range 334-434 K for reaction of Cl with CH3CH2I (k4(H)) and CD3CD2I (k4(D)): k4(H) = (6.53 +/- 3.40) x 10(-11) exp[-(428 +/- 206)/T] and k4(D) = (2.21 +/- 0.44) x 10(-11) exp[-(317 +/- 76)/T]. At room temperature and below, the reaction proceeds both via hydrogen abstraction and via reversible formation of an iodoethane/Cl adduct. Analysis of the LFP-RF data yields a binding enthalpy (0 K) for CD3CD2I x Cl of 57 +/- 10 kJ mol(-1). Calculations using density functional theory show that the adduct is characterized by a C-I-Cl bond angle of 84.5 degrees; theoretical binding enthalpies of 38.2 kJ/mol, G2'[ECP(S)], and 59.0 kJ mol(-1), B3LYP/ECP, are reasonably consistent with the experimentally derived result. Product studies conducted in the environmental chamber show that hydrogen abstraction from both the -CH2I and -CH3 groups occur to a significant extent and also provide evidence for a reaction of the CH3CH2I x Cl adduct with CH3CH2I, leading to CH3CH2Cl formation. Complementary environmental chamber studies of the reaction of Cl atoms with 2-iodopropane, CH3CHICH3, are also presented. As determined by relative rate methods, the reaction proceeds with an effective rate coefficient, k6, of (5.0 +/- 0.6) x 10(-11) cm3 molecule(-1) s(-1) at 298 K. Product studies indicate that this reaction also occurs via two abstraction channels (from the CH3 groups and from the -CHI- group) and via reversible adduct formation.     

Methane Pyrolysis Stimulated by Admixture of Atomic Hydrogen: 1. An Experimental Study

A method for enhancing the hydrocarbon pyrolysis process by introducing atomic hydrogen into the reaction medium from an arcjet plasma source was considered. It was shown that hydrogen atoms could effectively be introduced by mixing under low pressure. The atomic hydrogen–stimulated methane pyrolysis process was experimentally studied in a continuous stirred reactor with a plasma plume. When hydrogen atoms were present in the plasma jet, the amount of the valuable product increased by a factor of two.     

Li1-xMxFePO4阴极材料的合成和电化学性能

应用聚丙烯酸盐热解法合成掺杂Cr3+或Mg2+、Mn2+、Ni2+的LiFePO4正极材料,研究掺杂离子对目标化合物电化学性质的影响.XRD和SEM实验表明,该材料微米级颗粒是由约200nm的粒子团聚而成的,具有橄榄石型结构,且未出现杂质相.电化学测试表明,掺Cr3+的LiFePO4在高倍率(3C)放电下的首周放电容量为97mAh/g,相当于0.15C率容量的66%,其循环性能优异,充分显示离子掺杂能显著改善材料的高倍率放电性能和循环性能.     

苯并环丁二酮的热解法合成

报道了闪式真空热解法（Flah Vacuum Pyrolysis）合成取代的苯并环丁二酮。由取代苯酐经NaBH4还原得取代的羟基苯酞，其三氟乙酸酯在500－550℃及13.3-133.3Pa下经石英管热解，得相应的取代苯并环丁二酮，产率中等。     

Iterative solution of the master equation for thermal unimolecular reactions by the method of variable successive overrelaxation

A new algorithm which we have called the variable successive overrelaxation (VSOR) method is suggested to solve iteratively the master equation for thermal unimolecular reactions. The rate of convergence using this method is at least six times faster than using the well-known Tardy-Rabinovitch algorithm. A comparative study of various iterative techniques has been carried out on a well-known system (the thermal isomerization of cyclopropane-1.1-d₂).