Theoretical Study and NBO Analysis of the Decomposition Kinetics of Oxetane, 2-Methyloxetane and 2,2-Dimethyloxetane

A theoretical study of the thermal decomposition kinetics of oxetane (1), 2-methyloxetane (2), and 2,2-dimethyloxetane (3) has been carried out at the B3LYP/6-311+G**, B3PW91/6-311+G**, and MPW1PW91/6-311+G** levels of theory. The MPW1PW91/6-311+G** method was found to give a reasonable good agreement with the experimental kinetics and thermodynamic parameters. The decomposition reaction of compounds 1～3 yields formaldehyde and the corresponding substituted olefin. Based on the optimized ground state geometries using MPW1PW91/6-311+G** method, the natural bond orbital (NBO) analysis of donor-acceptor (bond-antibond) interactions revealed that the stabilization energies associated with the electronic delocalization from σC3-C4 bonding to σ*O1-C2 antibonding orbitals decrease from compounds 1 to 3. The σC3-C4→σO1-C2 resonance energies for compounds 1～3 are 2.63, 2.59 and 2.45 kcal mol-1, respectively. Further, the results showed that the energy gaps between σC3-C4 bonding and σ*O1-C2 antibonding orbitals decrease from compounds 1 to 3. Also, the decomposition process in these compounds are controlled by σ→σ* resonance energies. Moreover, the obtained order of energy barriers could be explained by the number of electron-releasing methyl groups substituted to the Csp3 atom (which is attached to oxygen atom). NBO analysis shows that the occupancies of σCsp3-O bonds decrease for compounds 1～3 as 3<2<1, and those of σCsp3-O bonds increase in the opposite order (3 > 2 > 1). This fact illustrates a comparatively easier thermal decomposition of the sCsp3-O bond in compound 3 compared to compound 2, and in compound 2 compared to compound 1. NBO results indicate that these reactions are occurring through a concerted and asynchronous four-membered cyclic transition state type of mechanism.     

反相高效液相色谱法同时测定人膀胱癌T24细胞中三磷酸腺苷及其代谢物的含量北大核心CSCD

所有生物过程都伴随着能量代谢,细胞内的能量供应主要依赖于线粒体合成的三磷酸腺苷(ATP)[1-2]。因此,建立有效的细胞内ATP及其代谢产物[二磷酸腺苷(ADP)和一磷酸腺苷(AMP)]的定量方法是非常有必要的。ATP、ADP和AMP的结构和理化性质非常相似,同时测定会有一定困难。     

气相中W~+活化CO_2分解的自旋禁阻反应机理

用密度泛函理论中的UB3LYP方法,对W采用相对论校正赝势基组(SDD),对C、O采用6-311+G(3d)基组,研究了气相中不同自旋态W+活化CO2分解的反应机理.计算结果表明,W+活化CO2分解反应以六重态进入反应通道,经过六重态势能面到四重态势能面的系间窜越(ISC),最后产物WO+和CO以四重态离开反应通道.运用Harvey方法优化出最低能量交叉点(MECP),并计算了MECP处的自旋-轨道耦合(SOC)常数(494.95cm-1),势能面的交叉和在MECP处较强的自旋-轨道耦合作用降低了自旋禁阻反应能垒,为反应提供了一条低能反应路径,反应总放热量为122.33kJ.mol-1.     

Adsorption of Benzene and Propylene in Zeolite ZSM-5： Grand Canonical Monte Carlo Simulations

The adsorption behavior of benzene and propylene in zeolite ZSM-5 was studied by Grand Canonical Monte Carlo(GCMC) simulations. It could be found that benzene and propylene molecules showed different adsorption behavior in the zeolite cavities. The loadings of propylene were significantly larger than those of benzene at 100 kPa. From the figures of potential energy distribution,the potential energy of benzene/zeolite was more negative than that of propylene/zeolite,so benzene could be adsorbed more stably t...     

大连化物所高比能量锂硫二次电池研究取得新进展

<正>近日,中国科学院大连化学物理研究所燃料电池研究部陈剑研究员领导的先进二次电池研究组(DNL0306组)在高比能量锂二次电池方面取得新进展,研制成功额定容量15 Ah的锂硫电池,并形成小批量制备能力。这是迄今世界上已见报道的容量最大的锂硫电池。第三方(中国科学院物理研究所)检测结果表明,电池的比能量大于430 Wh/kg,超过了Sion Power公司报道的由其研制的锂硫电池的技术指标     

钝体绕流的分隔板控制技术研究进展

钝体是工程中一种常见结构,流体绕过钝体时产生的旋涡脱落易诱发结构振动,进而导致结构破坏．钝体后安装分隔板是一种典型的被动控制技术,分隔板推迟钝体尾流区剪切层之间的相互作用,进而有效改变钝体后旋涡脱落及尾迹特性,延长结构寿命,并且可以利用钝体一分隔板结构进行能量收集．本文全面回顾了利用分隔板进行流动控制和能量收集的研究及...     

磁暴形态类型与行星际磁云特征

本文分析了6个不同特征的行星际磁云所引起的急始型磁暴形态的类型差别,得到的主要结论是:磁云前高密度结构是决定磁暴初相特征的重要因素;在磁云磁场强度相近的条件下,背景太阳风及磁云的速度均影响着磁暴主相的发展;磁暴强主相的开始及恢复决定于磁云磁场矢量相对于黄道面倾角的指向;强正磁云引起的磁暴的主要特征是主相长时间的延迟;磁云过后,太阳风流速仍继续影响着磁暴主相的恢复.