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《结构化学》1988,(1)
<正> A new quantitative relationship between the coupling constants 3JH-H of substituted ethylenes and the electronegativities Ex of the substi-tuents has been proposed. It can thus be conveniently used to estimate the values of 3JH-H of substituted ethylenes, thereby identifying the type of substituents and determining the molecular configuration of disubstituted ethylenes. It is shown from the calculations of 664 3J values carried out for 414 compounds that the standard deviation between the calculated and the experimental values is 0.26 Hz.In addition, it also provides a new method for determining the electronegativities of functional groups.The electrone-gativity data of 98 substituents determined so far suffice to indicate that most of them agree fairly well with Pauling's or revised Pauling's electrone-gativity data of a atoms in the substituents. 相似文献
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为了研究自然杂化轨道计算结果与核自旋偶合常数的相关性,本文进行了从头算级别的自然杂化轨道计算。采用STO-3G基组,利用Lowdin正交化原子轨道基组下的密度矩阵,得到了分子中各原子的杂化轨道、净电荷与^13C-H、^13C-^13C键自旋偶合常数^1Jcn和^1Jcc之间关系式。利用这些式子计算得到的结果与实验数据非常一致。 相似文献
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In this paper,calculations of force constants of molecular vibrations are carried out by using Wilson GF matrix method.In the determination of force constants from frequencies and factorization of Gmatrix,an ordering relationship of A matrix(may be n dimensional) relative to L matrix was found according to the ordering of symmetry coordinates.With the help of inverse unitary transformation,a general method to calculate Ft from constants Fs was established.The additivity of Fr depending on the symmetry block was determined to be true.All the force constants in non-planar and planar of urea,thiourea and sclenouroa molecules were calculated by using the general va-leine force field.The calculated values of frequencies were com-pairec with other data given in the literature,and it was shown that the present calculation is in good agreement with the experimental 相似文献
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《结构化学》1985,(3)
<正> The principle and method for calculating the chemical shifts of substituted benzenes have been extended to the calculation of chemical shifts in disubstituted naphthalenes. We have set up a series of empirical parameters for the calculation of chemical shifts. The calculated results of 439 8 values from 78 compounds show that the standard deviation between the calculated and the experimental values is 0.08 ppm. The combination of this calculation with that of the coupling constants can be used to provide a criterion .for the determination of molecular structure in disubstituted naphthalenes as well as to assign NMR parameters for the experiment of proton simulated spectra of disubstituted naphthalenes. 相似文献
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在研究自由基聚合反应动力学时,将单体浓度、引发剂浓度和溶剂浓度之间的摩尔比相对固定,并使之同步改变,由此获得一系列的R_p值。从时间—聚合转化率关系各直线部分截取转化率低于0.10质量分数、相对偏差小于±0.010质量分数的聚合物,测定它们的数均相对分子质量,于是关系式: 1/ _n=R_t/R_p+∑R_(tr)/R_p被简化为1/ =R_t/R_p+K链终止方式可从附表中判定。从1/ =k_1/K_p~2·R_p/c~2(M)+K(双基终止),1/ =k'_1/K_p·1/c(M)+K(单基终止)、或1/ =1/2·fk_dk_(prt)/(K_1·K_2)·c(I)/c~2(M)+K(初级自由基终止)计算出k_t/k_p~2·k_1'/k_p或1/2·fk_dk_(prt)/(k_1·k_p)值,并在各给定的实验条件下得C_1、C_s和C_M值。本文详细地阐述了1/ =K和1/ ≠K条件下计箅C_I、C_s和C_M值的实例。并由此佔价链转移反应机理。 相似文献
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《结构化学》1986,(3)
<正> The principle and method for the calculation of chemical shifts of substituted benzenes have been extended to calculation of the cheiiical shifts in substituted pyridines. We have set up a series of empirical parameters for calculation of the chemical shifts. The calculated results of 154 δ values frou 54 compounds show that the standard deviation between the calculated and the experimental values is 0 . 09 ppm. The combination of the coupling constants can be used to provide a criterion for the determination of molecular structure in substituted pyridines and to assign NMR parameters for the experiment of proton simulated spectra of substituted pyridines. 相似文献
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Additivity of substituent effects on the proton-proton coupling constants of disubstituted pyridines
From the spin-spin coupling constants of pyridine and monosubstituted pyridines the effects of several substituents have been calculated- Assuming an additivity relationship when two of these substituents are present in the same molecule, the spin-spin coupling constants for 11 disubstituted pyridines have been calculated.The NMR spectra of 13 disubstituted pyridines have been studied to obtain accurate values of their coupling constants. The experimental values of these constants are in very good agreement with those calculated using the additivity relationships. 相似文献
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V. Galasso 《Magnetic resonance in chemistry : MRC》1974,6(1):5-7
INDO–MO calculations have been performed on the ESR hyperfine coupling constants of the pyridinyl radical and the radical anions of pyrimidine, quinoline, isoquinoline, acridine and benzcinnoline. The nuclear spin coupling constants and the 14N nuclear quadrupole coupling constant of pyridine have also been calculated. In general, calculated values are in satisfactory agreement with the experimental data. 相似文献
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Coriolis coupling constants and the inertia defect for cis- and trans-1,2-dichloroethylene have been calculated, using force constants obtained by the iterative consistency method. The results obtained are compared with those of previous workers and it is shown that two sets of force constants which reproduce the vibrational frequencies satisfactorily lead to completely different values for the Coriolis coupling constants. 相似文献
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络合物稳定常数的计算 总被引:2,自引:0,他引:2
陈与德 《高等学校化学学报》1980,1(1):9
本文介绍了计算络合物稳定常数的八种方法,它们是:1.lgK1=Az2/r+Bx±+C.2.两相似金属离子与一系列配位体络合时,lgK1间一的线性关系。3.两相似配位体与一系列金属离子络合时,lgK1间的线性关系。4.一系列相似配位体与同一金属离子络合时,lgK1与∑pKa间的线性关系。5.一系列相近z2/r的金属离子与同一配位体络合时lgK1与x±间的线性关系。6.一系列相近x的金属离子与同一配位体络合时lgK1与z2/r间的线性关系。7.金属离子随z2/r和x而变化的络合次序。8.∑pKa较大的配位体与z2/r较大的金属离子匹配,电负性较小的配位体与电负性大的金属离子匹配。 相似文献
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Gupta VP Sharma A 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,65(3-4):759-769
A detailed analysis of the vibrational spectra of carbonyl cyanide, diethynyl ketone and acetyl cyanide has been conducted in harmonic and anharmonic approximations. RHF, MP2 and density functional theory (DFT) methods with 6-311++G(2df,2p) basis sets and B3LYP functionals have been employed. Spectroscopic constants such as anharmonicity constants, rotational and centrifugal distortion constants, rotation-vibration coupling constants and Coriolis coupling coefficients have been calculated for each molecule and compared with the experimental data, where available. A close agreement between the calculated and experimental values of the spectroscopic constants has been obtained. Complete assignments have been provided to the fundamental bands, overtones and combination tones of the molecules. Density functional theory based anharmonic frequencies compare well with the experimental frequencies within +/-18 cm(-1) on an average. RHF and MP2 methods, however, give much higher values for the frequencies that need scaling even in the anharmonic approximation. 相似文献
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温度对4-甲基丙烯酸2,2,6,6-四甲基哌啶醇酯与苯乙烯自由基共聚活性的影响 总被引:1,自引:0,他引:1
本文研究了4-甲基丙烯酸2,2,6,6-四甲基哌啶醇酯和苯乙烯在不同温度下的自由基共聚合反应。发现在石油醚、苯和二甲基甲酰胺等溶剂中,反应温度对共聚活性的影响不同。用NMR法测定了单体与溶剂的络合常数;计算了单体与溶剂相互作用的活化能和活化熵,依此对共聚活性与温度之间的关系进行了讨论。 相似文献