A force field study of diacetylene molecule by kinetic constant method

The potential constants of diacetylene molecule has been evaluated using kinetic constants. The other molecular constants such as the generalised vibrational mean amplitudes, shrinkage constants, Coriolis coupling constants and centrifugal distortion constants are also calculated using the vibrational frequencies and the results discussed.     

Molecular dynamics of germylacetylene

A complete vibrational analysis has been carried out for germylacetylene and germylacetylene-d₃ molecules and a set of molecular constants, i.e. kinetic constants and potential constants, is reported. The physical understanding of the nature of the potential constants and kinetic constants in molecules leads to a stringent application of provisions of group theoretical technique, introduced by Wilson in the study of molecular vibrations. This procedure is applied here to the evaluation of mean amplitudes of vibration. Coriolis coupling constants and centrifugal distortion constants of these cases, with highly satisfactory results. The values of Coriolis coupling constants and centrifugal distortion constants are in good agreement with the observed values for the germylacetylene molecule showing the significance of the procedure adopted in the present study.     

配合物的稳定性与配位体的酸碱强度之间的直线自由能关系VIII:N,N'-双(对位取代苯基)乙二胺与铜(II),镍(II)生成配合物的稳定性研究

在25℃, I=0.1mol.dm^-^3NaClO4的条件下,在混合溶剂[50%(υ/υ)二氧六环和70%(υ/υ)乙醇]中用pH法测定了N,N'-双(对位取代苯基)乙二胺的质子化常数及其与铜(II),镍(II)生成二元配合物的生成常数.结果表明:在配位体的质子化常数与配合物的生成常数之间,在配位体的σ'值与Hammett方程中的取代基常数σ之间,以及稳定化因子S~f与σ值之间,均存在着良好的线性关系.从实验进一步验证了在配位化学中直线自由能关系存在的普遍性.     

Ab initio study of spectroscopic constants and anharmonic force field of 74GeCl2

The equilibrium structure, spectroscopy constants, and anharmonic force field of germanium dichloride have been calculated at MP2, B3LYP, and CCSD(T) levels of theory employing two basis sets, cc-pVDZ and cc-pVTZ, respectively. The computed geometries, rotational constants, and vibration-rotation interaction constants, and quartic centrifugal distortion constants are compared with the available experimental data. The harmonic frequencies, anharmonic constants, and cubic and quartic force constants are predicted. The calculated results show that the MP2 results are in excellent agreement with experiment and represent a substantial improvement over the results obtained from B3LYP. The CCSD(T) method is also an advisable choice to study anharmonic force field of molecules.     

对、间位卤代苯甲酸在水-乙醇混合溶剂中电离过程的焓、熵贡献

用LKB-2277Bioactivity Monitor测定了25℃时间氯、对氯和对氟苯甲酸在水-乙醇混合溶剂中的标准电离焓, 计算了相应体系的标准电离熵。利用Hammett方程对溶剂中酸的取代基常数σ进行了计算, 求取了对应的焓、熵取代基常数σH和σS值及熵反应常数ρS, 利用内部-环境模型和上述常数对溶剂效应和取代基效应进行了解释。     

电导法测定杂多酸在非水溶液中的离解常数

本文以电导法测定了１２－磷钨、１２－硅钨酸在一些醇、酯、醛、酮等含氧有机溶剂以及乙腈中的离解常数，得到的结果表明，两种酸在同种溶液中的离解常数接近，磷钨酸的略高，同一种酸在不同溶剂中的离解常数则与溶剂的介电常数有密切关系。在醚中，因杂多酸与溶剂发生缔合作用，用电导法得不到其离散常数。     

Investigation of the extraction of some copper(II) chelates using isotope64Cu

The extraction of copper(II) 8-hydroxyquinolinate, 5,7-dichloro-8-hydroxyquinolinate and 2-thenoyltrifluoroacetonate was investigated and the stability constants and distribution constants of the complexes were determined. The dependence of thepH values for 50% extraction and of the distribution constants of the copper complexes on the dissociation constants and distribution constants of the corresponding agents are discussed.     

Structural effects on the rates of the ion molecule reactions of organic heterocycles

Rate constants for proton transfer reactions of seven heterocyclic amines, eight heterocyclic ethers and propylene sulfide have been measured by photoionization mass specrometry. Rate constants for dimerization of four sulfides have also been measured. The measured rate constants have also been compared to the theoretical (ADO) rate constants. In all cases the ADO rate constants show only small variations with structure. In fact for the mono-heterocycles all but one of the ADO rate constants are between 2.0 and 1.5 × 10^?9 cc molec^?1 sec^?1. The observed rate constants show considerable dependence on chemical structure. The amines react faster than the oxides which in turn react faster than the sulfides. N-Methyl substitution on pyrrolidine and piperidine lowers their rate constants by about a factor of two while, propylene oxide reacts eighteen percent faster than ethylene oxide. Examination of the variation in the observed rate constants as a function of ring size for each group of heterocycles indicates a distinct structure-reactivity correlation although we have not attempted to rationalize this correlation. There is also a structure-reactivity dependence observed in the six-membered oxygen heterocycles having a second heteroatom O, NH, or S in the 4-position. The rate constants increase with the electronegativity of the second heteroatom.     

Molecular dynamics of some X2Y3 systems

A complete vibrational analysis has been carried out for ¹⁰B₂O₃, ¹¹B₂O₃, and sulfur dicyanide and a set of molecular constants, i.e. kinetic constants, potential constants, compliance constants, vibrational mean amplitudes, Coriolis coupling constants and centrifugal distortion constants, is reported. The values of the centrifugal distortion constants of S(CN)₂, are in good agreement with the observed values, which bears out the significance of the method of kinetic constants adopted in this work.     

Theoretical study of anharmonic force field and spectroscopic constants for 1-chlorophosphaethene,CH2PCl and CD2PCl

The anharmonic force field and spectroscopy constants for CH₂PCl are determined using CCSD(T), VPT2, and density functional theory employing cc-pVQZ basis sets. The molecule structure, rotational spectroscopic constants, and vibrational wave numbers are compared with the available experimental data. Anharmonicity constants, vibration-rotation interaction constants and cubic force constants are predicted. Vibrational wave numbers and rotational constants for CD₂PCl are also determined using the same levels. The isotopic shifts of vibrational wave numbers are remarkable by D atom substitution for 1-chlorophosphaethene.     

Mathematical Modeling of Ru(VI)-catalyzed Oxidation of Alcohols by Hexacyanoferrate(III)

The title kinetics reaction has been modeled with a system of ordinary differential equations, for the concentrations of the compounds. In these equations, the velocity constants are unknown. In this work, the four constants had been evaluated by minimizing a mean squares expression comparing the experimental measures of the concentration of hexacyanoferrate(III) with the solution of the system of ordinary differential equations. This problem has not a unique solution and there is an infinite set of constants which minimize the expression. Several sets of possible constants have been analyzed. One of them has been obtained estimating two of the constants with the stationary state approach. For the model to be well posed the constants must fulfill a condition. Information about the order of magnitude of the constants has been reached.     

Chiral force constants: Recommendations for the presentation of internal coordinate force constants

Some force constants associated with the internal coordinates that sense handedness or chirality can have opposite signs in the enantiomers of chiral molecules. Examples of such force constants include interaction force constants between a torsional and stretching or bending internal coordinates. The sign reversal for these force constants in the enantiomers of chiral molecules or in opposite-handed molecular segments is best recognized by labeling them as chiral force constants. Recognition of chiral force constants suggests that certain guidelines are to be followed in the presentation of internal coordinate force constants. © 1993 by John Wiley & Sons, Inc. © John Wiley & Sons, Inc.     

Hydrolysis of Fischer carbene complexes. Steric effects of the pi-donor group

Rate constants for the hydrolysis of Fischer carbenes (CO)5Cr=C(OR)Ph (R = n-propyl, neopentyl, isopropyl, and menthyl) in 50% MeCN-50% water (v/v) at 25 degrees C are reported. The rate constants for the addition of -OH to the carbene carbon are 5.3, 3.7, 0.84, and 0.01 M(-1) s(-1), respectively. These rate constants give linear correlations with the corresponding rate constants for the hydrolysis of esters such as acetate, benzoate, and formiate. The slopes of the plots of the observed rate constants for the carbenes vs the rate constants for the esters are 1.4 and 1.2 for acetate and benzoate, respectively, indicating that the factors that decrease the reactivity of the two types of compounds are similar, but the carbenes show higher sensitivity. The rate constants are well correlated with several steric parameters giving a value of -3.84 for the Charton's psi parameter. The results show that the steric bulkiness of the R group is the main factor determining the reactivity differences for these carbene complexes.     

在胆汁酸盐背景中n种氨羧配位剂的加质子常数及其钙配合物稳定常数

为测定在胆酸盐和脱氧胆酸盐存在下氨提配位剂的加质子常数和钙配合物稳定常数,对常规电住法做了一些修正。用所建立的方法测定了EDTA、DTPA、EGTA及NTA的有关常数及其随胆汁酸浓度的变化。     

用诱导自洽方法计算振动力常数的研究

本文提出一种迭代方法计算振动力常数,可以比较清楚地显示基频与振动力常数之间的关系,从而能方便地选择合适的力常数限制条件,得到合理的结果.用本方法对一系列不同分子作了计算,结果比较满意,对计算中一些具体问题作了讨论.     

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.     

Spectrophotometric study of acidity constants of Alizarine Red S in various water-organic solvent

The acidity constants of Alizarine Red S were determined spectrophotometrically at 25 degrees C and at constant ionic strength 0.1 M (KNO3) in pure water as well as in aqueous media containing variable mole percentages (5-70%) of organic solvents. The organic solvents used were methanol, ethanol, N,N-dimethyl formamide (DMF), dimethyl sulfoxide (DMSO), acetonitrile and dioxan. The acidity constants of all related equilibria are estimated using the whole spectral fitting of the collected data to an established factor analysis model. DATAN program was applied for determining of acidity constants and pure spectra of different form of Alizarine Red S. The obtained results indicated that acidity constants decrease as the content of an organic solvent in the medium increases. There are linear relationship between acidity constants and the mole fraction of various organic solvents in the solvent mixtures. Effect of various solvents on acidity constants and pure spectrum of each component are also discussed.     

Determination of dissociation constants for some pyrogallol azo derivatives and stability constants of their complexes with rare-earth metals

The dissociation constants of some haloazo derivatives of pyrogallol and the stability constants of their complexes with rare-earth metals (La, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) are determined by potentiometric titration in aqueous ethanol (3: 7). A correlation between the dissociation constants of the reagents and the stability constants of their complexes is found.     

Potentiometric Study of the Chelates of Al(III), Ce(IV) and Th(IV) with Alizarin Red S

The stepwise metal-ligand stability constants of ARS chelates with Al³⁺, Ce¹⁺ and Th⁴⁺ have been determined by using Bjerrum-Calvin technique. Various computational methods were used to determine the stability constants. The thermodynamic stability constants were also calculated by determining the stepwise stability constants at various ionic strengths and then by extrapolating to zero ionic strength. The order of stability constants was found to be: Th>Al>Ce.     

A comparative study of the application of the method of least-squares in the potentiometric determination of protonation constants

Methods of simple and multiple linear regression applied to the potentiometric determination of protonation constants of diprotic and triprotic acids are studied critically. The best way of fitting the data, according to the order of magnitude of the constants, is established. The conclusions are checked by calculating the protonation constants of succinic and citric acids.