THE CALCULATION OF NUCLEAR SPIN-SPIN COUPLING CONSTANTS IX THE CALCULATION OF COUPLING CONSTANTS IN DISUBSTITUTED PYRIDINES

<正> The principle and Method for calculating the coupling constants of substituted benzenes have been extended to the calculation of coupling constants in disubstituted pyridines. The parameters 13 of some substi-tuents have been provided. The calculated results of 241 J values from 95 compounds show that the standard deviations between the calculated and the experimental values are within 0.11 Hz.     

芳杂环衍生物中环质子化学位移与取代基的关系

本文提出影响芳杂环衍生物中环质子化学位移的主要因素是取代基的电子效应及取代基位置.并根据取代基团的内部结构和它所在位置的关系,推导出一套经验公式,定量地预测氮苯类、噻吩类、呋喃类、五元氮芳杂环类和氮杂萘类等化合物的15种类型约300个芳杂环衍生物中700多个环质子的化学位移,与实测值相比,偏离在±0.2ppm内的约占88%,在±0.2～±0.3ppm的约占11%,大于±0.3ppm的<1%.     

ON THE PHOSPHORUS-31 CHEMICAL SHIFTS OF SUBSTITUTED TRIARYLPHOSPHINES

Abstract

The ³¹P chemical shifts of eleven (4-ZC₆H₄)₃P compounds show a slight correlation with the Hammet [sgrave]para constant of Z. The unusually large upfield chemical shifts of (2-ZC₆H₄)₃P compounds are attributed to an extreme “gamma” effect caused by the restricted conformations due to the steric influence of the ortho substituents. Chemical shifts are given for about thirty triarylphosphines, and group contributions to phosphine chemical shifts are listed for twenty-one aryl groups.     

SEMIEMPIRICAL CALCULATION OF THE INNER SHELL BINDING ENERGY SHIFTS IN MOLECULES INVOLVING SULPHUR ATOM

Abstract

The inner core binding energy shifts of sulphur atom in various chemical environments were studied by the semiempirical self-consistent charge molecular orbital method. The relaxation energy was taken into account by using two distinct approaches:(a) reorganizatinoo potential method and (b) transition potential method. The changes in ESCA chemical shifts of sulphur are satisfactorily accounted for by the latter method, the s tandard deviation from the experimental data being 0.2 eV. It appears that the reorganization energy plays an important role in rationlizing inner core binding energy shifts of sulphur.     

THE CALCULATIOM OF CHEMXCAL SHIFTS IN SUBSTITOTED PYRIDINES

<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.     

按独立组元计算复杂化学平衡的方法

本文通过分析独立组元的本质,提出了一个按独立组元来计算复杂化学平衡的方法。这个方法中的未知数和方程数比现有的自由能最小化法、质量作用方程组的方法和反应进度的方法中的未知数和方程数显著减少,因而计算过程大为简化。例如,对于计算一个由3个元素10个组元组成的复杂化学平衡体系来说,若采用其它方法须用电子计算机,而采用独立组元法仅须使用袖珍可编程序计算器即可完成。本文叙述了独立组元法的基本原理和具体方法,并根据理论分析和计算实践,将独立组元法与其它方法的优劣作了对比。     

EFFECT OF MAGNESIUM COMPLEXATION ON THE 31P MIDDLE-GROUP CHEMICAL SHIFTS OF CHAIN AND RING PHOSPHATES

Abstract

For pure sodium polyphosphates, Na _{n + 2}P _n O_{3n + 1}, exhibiting 3 through 6 phosphorus atoms per molecule, the ³¹P chemical shift of the middle group phosphorus atoms as measured in aqueous solution (0.1 M in P) at pH 7 was seen to increase with increasing magnesium ion concentration until there was one Mg atom per polyphosphate molecule, after which the chemical shift decreased. Finally the rate of decrease diminishes and precipitation occurs. For the longer-chain phosphates, Na _{n + 2}P _n O_{3n + 1} with n = 8, 9, 10, or an average of 100, as well as for the ring phosphates, Na _n P _n O_3n for n ranging from 3 through 10, an increase in magnesium concentration simply leads to a decrease in chemical shift which diminishes at the higher concentrations. These data lend additional support to the concept that polymerized phosphate anions in solution exist in preferred conformations which depend on the nature of the counteraction.     

UNUSUAL DOWNFIELD DEUTERIUM ISOTOPE SHIFT EFFECT ON THE 31P CHEMICAL SHIFTS OF DIALKYL BENZYLPHOSPHONATES

Abstract

A surprising linear downfield effect on the ³¹P chemical shift of a benzylphosphonate of deuterium substitution on the benzyl carbon has been noted. Its potential usefulness in mechanistic studies is suggested.     

THE ROLE OF THE LABORATORY IN CHEMICAL EDUCATION

The laboratory has been given a central and distinctive role in science education.The identity of the best kinds of experiences and how these may be blended with more conventional learning experiences has not yet been objectively evaluated.A clear direction for laboratory instruction based on research is not yet available to teaching chemists.     

LIGHT-INDUCED SHIFTS IN THE ABSORPTION SPECTRUM OF CAROTENOIDS IN RED AND BROWN ALGAE

Abstract— Changes in light absorption in the region 450–540 nm were observed upon illumination of the red algae Iridaea splendens, Schizymenia pacifica and Porphyra perforata and the brown alga Pheostrophion irregulare . The difference spectra of these changes in Iridaea and Schizymenia showed maxima and minima at about 465, 480, 495, 515 nm. The spectra were similar to difference spectra earlier observed in photosynthetic bacteria, and the location of the maxima and minima suggested a shift towards longer wavelength of a compound with absorption maxima at about 440, 470, and 500 nm, probably a carotenoid. Similar, but more distorted difference spectra were observed in the other algae. Time courses and size of the signals induced by light of different wavelengths suggest that excitation of both photosynthetic pigment systems causes a shift in carotenoid absorption, with kinetics which appear to be similar to those of the well-known change at 515 nm in green plants.     

THROUGH-SPACE INTERACTION OF TETHERED GROUPS IN DIPHOSPHA PERI-SUBSTITUTED NAPHTHALENES

NMR properties of 1,8-diphosphanaphthalenes with prerequisites for strong through-space interaction were studied. The exceptional magnitude of ⁴J(PP) 246 Hz was found in Nap[P(NMe₂)₂][P(OMe)(NMe₂)] (Nap = naphthalene-1,8-diyl). The P^III, P^V mixed valence systems Nap[P(E)(OMe)₂][P(OMe)₂] (E = O, S, Se) show much lower magnitudes of through-space interaction than expected.     

THE CORRELATION BETWEEN ~(13)C CHEMICAL SHIFTS OF DNA AND INTERSTRAND PURINE-PURINE CLASH

The correlation between ~(13)C chemical shifts of DNA and structure parameters (the mainaxis helix twist angle Ω, base--plane roll angle ρ, main chain torsion angle δ and pro-peller twist angle ω) has been discovered and proved indirectly. The carbons relating tothe structure parameters have been found and interpreted theoretically. Relative variationsin chemical shifts of these carbons obviously reflect purine-purine clash (steric hindrance)and have been compared with sum functions Σ of Calladine--Dickerson rules. It would bepossible to provide the information about conformation of DNA from ~(13)C NMR spectra andto observe the structure parameters of Ω,ρ,δ and ω of DNA in solution.     

包括d轨道的NMR化学位移的INDO/GIAO微扰理论

本文推广了计算~(18)C化学位移的INDO/GIAO方法,以进行~(15)N、~(17)O以及过渡元素配合物的~(18)C化学位移计算。通过N,O及Fe的INDO参数的优化选择,计算的~(15)N、~(17)O以及配合物(C_5H_5)Fe(CO)_2CN,(C_5H_4)_2Fe(COH)_2及(C_5H_4)_2Fe(CH_2OH)_2的~(18)C化学位移符合实验结果,同时发现计算的原子净电荷ρ(M)和σ~d(M)之间存在良好的线性关系。     

SOME PRESUPPOSITIONS IN THE METAPHYSICS OF CHEMICAL REACTIONS

The project of chemistry to classify substances and develop techniques for their transformation into other substances rests on assumptions about the means by which compounds are constituted and reconstituted. Robert Boyle not only proposed empirical tests for a metaphysics of material corpuscules, but also a principle for designing experimental procedures in line with that metaphysics. Later chemists added activity concepts to the repertoire. The logic of activity explanations in modern times involves hierarchies of activity concepts, transitions between levels through non-dispositional groundings. Such hierarchies terminate in powerful particulars, such as elementary charged particles. Do these have a fundamental place in the most recent accounts of molecular architecture, stabilities and transformations? However, a close study of the contemporary chemistry of substances transforming reactions discloses a hybrid metaphysics, making use of both the Boylean corpuscles and Faradayan fields. This is illustrated by an analysis of the metaphysics inherent in John Polanyi’s use of “chemoluminescence” to follow the formation of products in chemical reactions. A brief sketch of a resolution of the tension between the two metaphysical schemes is drawn from Niels Bohr’s radical metaphysics extended from the quantum realm proper to chemistry (and perhaps beyond).     

化学计量学在分析化学中的应用

从化学定量构效关系、模式识别法、人工神经网络、波谱化学、多元校正分析法等方面对化学计量学在分析化学中的应用进行了综述。阐明了化学计量学在分析化学中的作用及广阔的应用前景。     

方差分析在化学助剂评价中的应用

介绍用方差分析的方法处理化学助剂评价试验的数据,有效去除试验误差对评价的影响,使评价的结论科学,合理,而又正确。     

内氢键对芳环~(13)C化学位移的影响

本文讨论水杨醛、邻——基苯乙酮及2——基雌甾化合物的分子内氢键对芳环~13C化学位移的影响。采用量子化学CNDO/2方法,计算取代芳烃各原子的净电荷,从碳原子的净电荷与化学位移的对应关系进一步论证了此种影响.首次得到形成内氢键的甲甲基、乙乙基及及基对所在碳的取代基增量的校正值,经校正后化学位移的计算值与实测值很好符合。     

慈竹沥化学成分的研究

慈竹沥化学成分的研究黄世德，夏厚林，卢先明，高景莘（成都中医学院中药系６１００７５）关键词：慈竹沥，氨基酸，有机酸，酚类还原糖中药竹沥具有清热化痰的功效，临床上用于治疗肺热咳嗽痰多、气喘胸闷、中风舌强、痰涎壅盛、小儿痰热惊风等疾患［１］。传统中药竹沥...