CX_3NO(X=H,F,Cl)分子结构稳定性的Ab initio研究

CH_3NO(1)、CH_2FNO(2)、CHF_2NO(3)、CH_2ClNO(4)、CHCl_2NO(5)、CHCIFNO(6)、CF_3NO(7)和CCl_3NO(8)是一类重要的光化学分子,它们稳定性差、寿命短,实验研究其结构及稳定性较困难,仅CH_3NO、CF_3NO和CCl_3NO分子有理论研究,其余均未见报道,本文用ab initio方法在STO-3G水平上研究了上述分子结构稳定性,还用STO/     

钒硫团簇V2S2+、V3S4+的结构和稳定性

用ab initio分子轨道方法(RHF,UHF)和密度泛函(DFT)方法研究了团簇V2S2+、V3S4+的各种可能的几何构型和电子结构,所得理论计算能较好地解释有关实验结果.     

钴硫团簇ConSn+-1(n=2,3)的结构和稳定性

用ab initio分子轨道方法(RHF,UHF)和密度泛函(DFT)方法研究了团簇Co2S+,Co3S2+的各种可能的几何构型和电子结构,并计算了相应的较稳定构型的振动光谱,发现Co2S+和Co3S2+团簇最稳定结构均具有C,对称性.对团簇的成键作用机理进行了理论分析.     

CX_3NO(X=F、Cl)分子结构和稳定性的ab initio研究

本文用STO-3G基组对分子CF_3NO(1)、CF_2ClNO(2)、CFCI_2NO(3)和CCl_3NO(4)的各种可能存在的稳定构型进行了研究.结果表明:(1)卤素与氧在同侧的构型比其它构型稳定;(2)在同一分子中,Cl与O同侧比F与O同侧更为稳定;(3)分子从1至4稳定性下降.本文计算结果与实验符合较好。     

CX3NO(X=F、Cl)分子结构和稳定性的ab initio研究

本文用STO-3G基组对分子CF_3NO(1)、CF_2ClNO(2)、CFCI_2NO(3)和CCl_3NO(4)的各种可能存在的稳定构型进行了研究. 结果表明:(1) 卤素与氧在同侧的构型比其它构型稳定; (2) 在同一分子中, Cl与O同侧比F与O同侧更为稳定; (3) 分子从1至4稳定性下降. 本文计算结果与实验符合较好。     

CO2与HCN,NH3,H2O分子络合物的从头计算研究

用ab initio能量梯度法(3-21G基组)分别优化CO_2与HCN、NH_3、H_2O_3个分子络合物的平衡几何构型。结果表明HCN、NH_3和H_2O中的N或O原子与CO_2中的C原子之间形成较弱的范德华键,三者的范德华键键长分别为0.2865、0.2775、0.2543nm,稳定化能分别为14.8、27.0、31.2kJ·mol~(-1),3个分子络合物的构型都呈T型,对3个分子络合物的稳定化能的能量分解研究表明它们的形成主要靠静电作用能。     

B~4元素簇的结构与成键特征

在ab initio 6-31G水平上, 用能量梯度法优化了不同构型B~4元素簇的几何结构参数。用组态相互作用方法对相应于7种几何构型的8个电子态, 进行了相关能计算。通过简正坐标分析, 确证了三种稳定构型, 其对应态的能序为:1^Ag(D~2h)<1^A~1(C~20)<3^A~a(T~d)>1^A~1(T~b)。此外, 用定域化分子轨道方法对稳定态的成键性质进行了讨论。     

亚烷基卡宾与亚烷基锂氟类卡宾化学键结构的量子拓扑研究

用ab initio(3-21G)方法对亚烷基卡宾H_2C—C的单线态及三线态结构进行了电子密度拓扑分析,说明了它们的亲电、亲核反应方向,讨论了亚烷基锂氟类卡宾H_2C—CLiF的4种构型,论证了该分子中不存在四元环结构、Li—C键以静电作用为主的特性,并预测了加成反应机理。     

乙醛二聚体的从头计算

用ab initio分子轨道法在STO-3G和6-31G水平上, 全构型优化, 对二聚乙醛的各种稳定构型进行了研究。结果表明, 在STO/6-31G水平上, 最稳定的乙醛二聚体为具有对称中心的环状结构, 包含由醛基氢和醛基氧组成的二个C—H…O氢键。结合能为-20.17 kJ·mol~(-1), 与实验估计的结合能-22.39±0.15 kJ·mol~(-1)比较接近。STO-3G过低估计了乙醛二聚体的结合能, 在不同构型的相对稳定性方面也与6-31G不一致。     

C4Om-4(m=0,1,2,3,4)的从头算研究 2.化学键、电离势和振动频率

在第1报优化的几何构型的基础上,用Boys定域化方法和QSU90程序计算了C4Om-4(m=0,1,2,3,4)的定域化分子轨道,讨论了其成键特征和电离势.在6-31G水平用ab initio解析方法计算它们的谐振动频率.     

CF3C(O)F水合作用的热力学和动力学理论研究

由于氟氟烃（CFCs）对大气臭氧层有破坏作用，人们拟以另外的化合物来代替它，CF3CX2H（X＝H，CI，F）可能是一类合适的取代物．但人们对它及其反应产物对大气的影响还不清楚.CFaC（0）F是CFaCX。H大气光氧化过程的终产物之一[1－3］，其在大气中的后继反应行为将直接关系到CF2     

双自由基CF2与O3的反应机理

主要用作致冷剂和发泡剂的氯氟烃（CFCs）是破坏臭氧层的主要物质之一．对氯氟烃类化合物及其降解产物（包括光解、光氧化、化学反应产物等）在大气中行为问题的研究是大气化学研究的重要内容．前人[1-3]从理论和实验两方面研究了自由基与臭氧的反应机制，但是氯氟烃光解过程中     

CF3CO和CF3C（O）O自由基分解反应理论研究

利用文献结果，用统计热力学和过渡态理论计算了ＣＦ３ＣＯ和ＣＦ３Ｃ（Ｏ）Ｏ自由基分解反应的热力学和动力学数据。计算结果表明，计算值与最新实验数据甚相符合，并据此判断，ＣＦ３ＣＯ和ＣＦ３Ｃ（Ｏ）Ｏ均很不稳定，不可能参加Ｏ３分解的循环催化反应。     

Synthesis and Crystal Structure of Mn(phen)(CF_3COO)(H_2O)_3·NO_3

1 INTRODUCTION The manganese(II) ion is a biologically essential element. Knowledge of its importance is increasing as more and more enzymes are found to contain manganese ions at the active center[1, 2]. The X-ray crystallographic structures of a consi…     

Semiempirical (AM1) and ab initio calculations of 2-X-adenine (X = H, F, Cl) and β-D-1-amino-2,3-didehydro-1,2,3-trideoxyribofuranose

We performed semiempirical (AM1) and ab initio (3-21G and 4-31G^**) calculations, with complete optimization of geometry, for 2-X-adenine (X = H, F, Cl) and selected conformers of β-D-1-amino-2,3-didehydro-1,2,3-trideoxyribo-furanose. Together (as 2-X-2',3'-didehydro-2',3'-dideoxyadenosine), or in separate conjunction with similar fragments, these structures belong to a group of 2',3'-dideoxynucleosides with potential anti-HIV activity.

The 2-X-adenine molecules are basically flat. For the halogenated species, especially the chlorine derivative, the results of the semiempirical method differ from the ab initio findings more widely than for adenine.

The results for the ribose derivative show the existence of conformers differing very little in energy. Ring puckering does not appear to depend on exocyclic torsion angles, structures with different conformations around the exocyclic C-C bond having similar ring conformations in all the cases analysed. The AMI method yielded geometries similar to those obtained ab initio with 3-21G.     

Vibrational spectra, structure, and theoretical calculations of 2-fluoro- and 3-fluoropyridine

The infrared and Raman spectra of liquid and vapor-phase 2-fluoropyridine and 3-fluoropyridine have been recorded and assigned. Ab initio and DFT calculations were carried out to compute the molecular structures and to verify the vibrational assignments. The observed and calculated spectra agree extremely well. The ring bond distances of the fluoropyridines are very similar to those of pyridine except for a shortening of the C-N(F) bond in 2-fluoropyridine. The C-F bond stretching frequencies are similar to that in fluorobenzene reflecting the influence of the ring π bonding.     

Infrared and Raman spectra, ab initio calculations of structure and vibrational assignment of 1-fluoro-2-butyne.

The infrared spectra (3500-50 cm(-1)) of the gas and solid and the Raman spectra (3500-50 cm(-1)) of the liquid and solid have been recorded for 1-fluoro-2-butyne, CH3-C-triple bond-C-CH2F. Equilibrium geometries and energies have been determined by ab initio and hybrid DFT methods using a number of basis sets. A vibrational assignment is proposed based on the force constants, relative intensities, depolarization ratios from the ab initio and DFT calculations and on vibrational-rotational band contours obtained using the calculated equilibrium geometries. From calculated energies it is shown that the CH3 group exhibits almost completely free rotation which is in agreement with the observation of Coriolis sub-band structure in two of the degenerate methyl vibrations. The results are compared to the corresponding quantities for some similar molecules.     

连续二氧化碳激光敏化氧化CF2HCL,CF2=CF2,CF2=CFCl,CHCl3,CHCl=CCl2和CH2=CH2

本文报道了连续二氧化碳激光敏化氧化CF_2HCl,CF_2==CF_2,CF_2==CFCL,CHCl_3,CHCl==CCl_2和CH_2==CH_2的反应,讨论了某些反应的机制。结果表明,激光敏化方法可以使不能直接吸收激光的反应物分子在气相中发生反应,并有可能产生卡宾。     

Conformational stability of CH3CH2PH2BH3 from temperature dependent FT-IR spectra of xenon solutions and r0 structural parameters

Variable temperature (-55--100 degrees C) studies of the infrared spectra (3500-400 cm(-1)) of ethylphosphine-borane, CH3CH2PH2BH3, and ethylphosphine-borane-d5 dissolved in liquid xenon have been recorded. From these data, the enthalpy difference has been determined to be 86 +/- 8 cm(-1) (1.03 +/- 0.10 kJ/mol), with the trans conformer the more stable rotamer. Complete vibrational assignments are presented for both conformers, which are consistent with the predicted frequencies obtained from the ab initio MP2/6-31G(d) calculations. The optimized geometries, conformational stabilities, harmonic force fields, infrared intensities, Raman activities, and depolarization ratios have been obtained from RHF/6-31G(d) and/or MP2/6-31G(d) ab initio calculations. These quantities are compared to the corresponding experimental quantities when appropriate as well as with some corresponding results for some similar molecules. The r0 structural parameters have been obtained from a combination of the previously reported microwave rotational constants and ab initio predicted parameters.