基团电负性研究 VI. 基团电负性与烷基衍生物的标准生成热

本文试用前文建立的基团电负性, 通过研究ΔΔFH°(RX/CH3X)与基团电负性xG的定量关系, 从而建立一个简单方法用以计算几乎所有烷基衍生物RX(X=F, OH, Cl, NH2,Br, SH, I, OH3)的标准生成热。     

基团电负性研究——Ⅵ.基团电负性与烷基衍生物的标准生成热

本文研究了基团电负性x_G与标准生成热的差值[⊿⊿_f H°(RX/CH_3X)=⊿_fH°(RX)-⊿_fH°(CH_3X)]之间的定量线性关系,从而建立了一个计算烷基衍生物标准生成热的简单方法:⊿_fH°(RX)=⊿_fH°(CH_3X)+a_mx_G+b_m式中,R为烷基;X代表F,Cl,Br,I,OH,NH_2,SH和cH_3;x_G为基团X的电负性;a_m和b_m是与烷基结构相关的常数.计算的平均偏差为1.94kJ/mol.该法可进一步用于估算其它烷基衍生物的标准生成热.     

基团电负性与含氧有机物的标准生成热

本文利用作者提出的基团电负性,建立了一个计算含氧有机物标准生成热的简单方法: △fH°(RZ)=△fH°(CH_3Z)-(0.48 n~(1/2)+17.18)x_G-20.13n+69.71式中,△fH°(RZ)和△fH°(CH_3Z)分别为含氧有机物RZ和CH_3Z的标准生成热;Z-OE_e、OM_e、OH、COCH_3、CHO、CO_2H、CO_2Me、CO_2Et.CONH_2;x_G为基团Z的电负性;n是直链烷基R中的碳原子个数,48个可比较值的平均偏差为0.3kCal/mol。     

一种计算基团电负性的简单方法

基团(取代基)电负性在研究复杂分子特别是有机化合物的结构和性质中是一个重要参数。人们在这方面已作了许多工作,文献报道的基团电负性值不少于十套。但这些方法大都太繁,公式复杂且参数较多,不便运用。本文试以核磁共振谱的质子化学位移值为依据,建立一个简单的计算公式。人们熟知,核磁共振谱中的质子化学位移与围绕质子的电子密度相关,而质子周围的电子密度又与邻近的取代基的基团电负性紧密相关。电负性大的基团     

基团电负性的简易计算方法

本文建立了一种只利用pauling电负性数据直接计算各类非共轭共价基团的电负性的方法,并讨论了用电负性解释分子物理性质和化学性质的一些例子.     

电负性的研究——Ⅱ.基团电负性

近十余年来,许多学者^[1-7]对基团电负性作了不少研究工作,并提出多种计算基团电负性的方法。其中,除wilmshurst^[6],Hinze等^[7]外,所有的基团电负性都是在某种实验数据中找出经验公式而求得的。在推导这样的经验公式时,往往能够用同一方法处理的化合物的数目有限,因而公式的应用不免受到一些限制。     

超原子理论计算基团电负性的研究

依据Bratsch计算基团电负性的方程,根据Pauling原子电负性标度,提出了一种计算较大基团电负性的方法,该方法基于超原子思想。使用该方法做了大量的基团计算,并和引用其他文献计算结果做对比,结果表明提出的方法更加适用于计算较大的基团。     

逐级均分法计算基团电负性

基团电负性在化学中是一个非常重要的参数。关于基团电负性的计算，已有很多文献报道，但多数方法公式比较繁杂、或者是因为依赖于特殊的实验数据而受到一定的限制。本文在sanderson电负性均等原理的基础上，提出了一种简单的计算方法一逐级均分法。     

逐级均分计算基团电负性方法的改进

最近,李朝恩等在 Sanderson 电负性均等原理基础上,提出用逐级均分法计算基团电负性。他们认为,直接键连的基团或与一个     

基团电负性与烷基衍生物的标准汽化热

基团电负性与烷基衍生物的标准汽化热韩长日（湖北师范学院化学系黄石４３５００２）关键词：标准汽化热，基团电负性，烷基衍生物前言汽化热是反映液体分子间相互作用力大小的重要热力学参数。尽管热力学数据的实验积累要比化学其它领域的数据的实验积累丰富得多，但对于...     

基团电负性研究(Ⅹ)——基团电负性与XSiRxH3-x的标准生成热

由于含硅有机物测量所需纯样的制备困难,且有些含硅有机物燃烧不完全,难以用氧弹量热法准确测定生成热,所以它们的标准生成热大多未见报道^[1,2],而这些数据又是研究有机硅化学热力学和反应性的重要参数,因此有必要建立一套简单而准确的估算方法^[2].     

Molecular orbital electronegativities of transition metal fragments: A MO approach based on the transition operator method

The molecular orbital electronegativities χ of various transition metal fragments have been investigated by means of the “transition operator (TO) method” within a semi-empirical INDO Hamiltonian. The calculated electronegativities χ(TO) are discussed with respect to the donor and acceptor properties of the studied complexes. It is found that the values χ(TO) can be correlated with experimental and theoretical data concerning the nature of the chemical bond in transition metal derivatives.     

Correlations between F NMR chemical shifts and bond dissociation energies, enthalpies of formation and group electronegativities

Correlations between ¹⁹F NMR chemical shifts (Φ) in fluorohalohydrocarbons and enthalpies of formation, bond dissociation energies, group contribution to enthalpies of formation and enthalpies of formation of free radicals are presented. A good correlation between these properties has been found with the square root of Φ. A relationship between fluorine chemical shifts and group electronegativities is also discussed.     

A molecular electrostatic potential bond critical point model for atomic and group electronegativities

A consistent set of atomic electronegativities of main block and d-block transition elements has been obtained from the position and value of the molecular electrostatic potential bond critical point of the C-E bond of a methyl-element-hydride system, H(3)C-EH(n) (E is an element and n = 0, 1, 2, 3, 4, and 5 depending on the position of E in the periodic table). The new scale shows very good agreement with the popular electronegativity scales such as Pauling, Allen, Allred-Rochow, Mulliken, and Sanderson scales of electronegativity, especially for the main block elements. The present scale of electronegativity for transition elements is expected to be more accurate than the previously derived values because of a more consistent approach. Further, the same approach has led to the evaluation of group electronegativities when the hydrogens of E are replaced by other substituent groups. These group electronegativity values are found to correlate well with Inamoto and Mullay scales.     

Electronegativities from core-ionization energies: electronegativities of SF5 and CF3

Core-ionization energies have been measured for SF(6) (S 2p), SF(5)SF(5) (S 2p), SF(5)Br (S 2p and Br 3d), and SF(5)CF(3) (S 2p and C 1s). These results, together with others that establish correlations between core-ionization energies and Pauling electronegativities, make it possible to assign group electronegativities to SF(5) and CF(3). This method gives electronegativities for these groups comparable to that of bromine, whereas analysis of the effect of these groups on acidity indicates electronegativities comparable to that of fluorine. Other methods of estimating electronegativity fall between these extremes. These disparities can be understood in part as reflecting the effects of polarizibility of the substituent, which tends to lower both the core-ionization energy and the deprotonation energy, making the electronegativity appear to be less in one case and more in the other. In addition, and possibly more important, the core-ionization energies presented here reflect the effect of the group on an adjacent atom, whereas the acidity reflects the effect on a remote atom. It appears that fluorine has a large effect on an adjacent atom but a relatively small effect on a remote atom. By contrast SF(5) and CF(3) have a relatively small effect on an adjacent atom, but this effect falls off only slowly with distance from the substituent. Thus, the effective electronegativities of CF(3) and SF(5) relative to those of the halogens depend on the site at which the molecule is probed as well as on the process that is under consideration.     

A new scale of atomic electronegativities

A new formula for the calculation of atomic electronegativities from the atomic size and nuclear effective charge is proposed. The formula has the same dimensionality as the one used for the thermochemical scale. The calculated ionic and van der Waals atomic electronegativities are used for the interpretation of the bond nature in binary and coordination compounds (in particular, the bond ionicity is calculated in molecules and crystals of the AB type).Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 32–37, January, 1993.     

烷基衍生物标准生成焓的QSPR研究

根据分子拓扑理论,建立了一个新的拓扑指数Y~X,并用Y~X对不同系列烷基衍生物M~nL(n=1,2,3;L=F,OH,Cl,NH~2,Br,SH,I;M=Me,Et;i-Pt,t-Bu,n-Pr,n-Bu,Amyl)的标准生成焓-△~fH~m^θ进行拟合,其相关系数均在0.999以上。计算结果表明,新的拓扑指数易于计算,物量意义明确,具有良好的结构选择性和性质相关性。该法可进一步用于估算其它烷基衍生物的标准生成焓。     

19F spectra—structure correlations of fluorinated quaternary phosphonium salts

The ¹⁹F NMR chemical shifts and geminal FCP and FCH coupling constants are reported for a number of fluorinated quaternary phosphonium salts of the type \documentclass{article}\pagestyle{empty}\begin{document}$ [{\rm R}_3 \mathop {\rm P}\limits^ \oplus {\rm CFXY}]{\rm Z}^ \ominus $\end{document}, where generally R = alkyl or aryl; X, Y = hydrogen or halogen and Z = halogen. Spectral parameters remain relatively unaffected upon variance of R, Z^?, and/or solvent, except when R is a bulky alkyl group. Linear relationships accurately describe the correlation between the summation of the electronegativities of X and Y, or simply of Y if X = F, and the ¹⁹F NMR chemical shift and geminal FCP coupling constant; geminal FCH coupling constants show no such dependence. These relationships are of demonstrated analytical value, particularly for the purpose of spectral prediction.     

Dimethoxycarbonyl Groups Surrounding a Symmetric Diaminobistetrazole Ring: Exploring New Green Energetic Materials

A novel oxygen‐containing dimethoxycarbonyl diaminobistetrazole ( 1 ) was synthesized via a facile strategy. The sodium salt ( 2 ) based on this ligand was prepared and these two compounds were fully characterized by using elemental analysis, IR and mass spectrometry and single‐crystal X‐ray diffraction. Their density, heats of formation, thermal stability and sensitivity, as well as the energetic properties from EXPLO5 code were investigated. These newly synthesized compounds possess high positive heats of formation and detonation heats. Compound 1 exhibits good detonation performance and acceptable stability, and might be a potential eco‐friendly alternative of lead azide. The present study contributes to the development of tetrazole derivatives as new energetic materials.     

异质富勒烯C58P2的理论研究

用ＭＮＤＯ半径能方法研究了异质富勒烯Ｃ５８Ｐ２各异构体的结构和相对稳定性。结果表明,１,４－位取代的异构体最稳定,异构体的稳定性随杂原子同距离的增加而降低。Ｃ５５８Ｐ２分子和稳定性比全碳富勒烯Ｃ６０低,但仍具有相当的稳定性,是潜在的合成目标。杂原子磷的掺杂改善了富勒烯的氧化还原性能。考察了各异构体的整体硬度和绝对电负性,产根据绝对电负性的差异预测了富勒烯和异质富勒烯间形成聚合物时的电子转移。