Polarization effect in the sorption and retention of sorbates in gas chromatography

The influence of substituents on the chromatographic retention parameters is investigated. With six series of substances, it is shown that the considered parameters correlate with the Hammett-Taft constants. It is established that, in gas adsorption and gas-liquid chromatography, the influence of substituents on the retention parameters is a combination of three components: inductive, resonance, and polarization effects.     

Methylpyridylbenz-X-azoles. lH NMR Study

The shielding parameters of benz-X-azolyl substituents in various positions of the pyridine nucleus were determined by means of a regression analysis procedure. Analogously the shielding contributions of pyridyl substituents on homocyclic protons of benz-X-azoles were derived. The results evidence some interactions between the two heterocyclic systems when the benz-X-azolyl substituents are linked at the pyridine α-position.     

Charge density and NMR parameters. Aliphatic derivatives

The charge distribution in several substituted aliphatic derivatives was determined by a parametric MOLCAO method. The charges were successfully employed to interpret NMR parameters, namely proton and carbon chemical shift and vicinal proton-proton coupling constants in ethyl derivatives and carbon-proton coupling constants. The linear correlations found between NMR parameters and charge densities are restricted to substituents of the same row of the periodic system. The decay along the aliphatic chain of the perturbation induced by substituents on proton chemical shift is also reproduced by charge distribution. Some results also seem to indicate that the substituents affect the hybridization of the attached carbon atom.     

127I and79Br NQR spectra of halo-substituted phenols and phenylmercury phenoxides

The full¹²⁷I NQR spectra of a series of iodo-substituted phenols and phenylmercury phenoxides have been studied. The quadrupole coupling constants and asymmetry parameters have been determined. The character of the OH...Hal hydrogen bond has been found to depend on the nature of substituents in the ring. Correlation dependences of the asymmetry parameters on the sum of the substituents resonance constants have been found for both coordinated as well as for non-coordinated iodine atoms.     

O-烷基O-取代苯基硫代磷酰胺酯类化合物的合成及其结构与杀虫活性的定量关系

合成了19种O-烷基O-取代苯基硫代磷酰胺酯类化合物,在定量测定其杀虫活性的基础上,对该类化合物进行了结构与活性定量关系的解析。结果表明,分子中芳基上取代基的电子效应与2,3-位上取代基的疏水性质对活性有重要影响。     

Effect of bulky substituents on the photochromic properties of indoline spiropyrans containing an annelated aromatic or heteroaromatic fragment

Novel indoline spiropyrans containing bulky neopentyl substituents at the nitrogen atom of the indoline fragment were prepared. The structure of the obtained compounds was established by a set of physicochemical methods of analysis. Comparison was made for the spectral absorption and kinetic parameters of the obtained compounds and their analogs containing methyl and benzyl substituents instead of neopentyl ones.     

Processus de rotation empéchée autour de la liaison C?N dans les anilines

In anilines, intramolecular exchange of amino protons appears at low temperatures. Relations between activation parameters and electronic effects of substituents are studied and NMR parameters discussed.     

Quantitative Studies on Structure－Activity Relationships （QSAR） of Cytokinin－Active Phenyl Urea Derivatives（PUD）

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The influence of the nature of substituents on adsorbability and the rate of liquid-phase hydrogenation of nitrobenzenes

The influence of the nature of substituents on the rate of liquid-phase hydrogenation of nitrobenzenes on Raney nickel was studied in an aqueous solution of 2-propanol. Interrelation between the rate of the reaction on the equiaccessible surface of the catalyst and solvation parameters, reactivity indices, and adsorption values of hydrogenated compounds containing electron acceptor (4-nitrobenzoic acid) and electron donor (4-nitroaniline) substituents was considered.     

Carbon-13 magnetic resonance studies of cyclic compounds. 2. Carbon-13 chemical shift parameters for equatorial and axial substituents in cyclohexane: The substituents methyl,ethyl, isopropyl,methoxy and phthalimido

Carbon-13 chemical shift parameters for equatorial and axial substituents in cyclohexane are reported for methyl, ethyl, isopropyl, methoxy and phthalimido substituents. The usefulness of the alkyl parameters is demonstrated by the agreement between calculated and observed ¹³C shifts for trans-1,4-dialkylcyclohexanes (alkyl = Me, Et, i-Pr) and for both conformations of cis-1,4-dialkylcyclohexanes (alkyl = Me, Et, i-Pr).     

Structure-reactivity correlation in the pyridinolysis of substituted phenyl acetates

The pyridinolysis of substituted phenyl acetates in acetonitrile was investigated with an electric conductivity method. The rates of these reactions were increased with electron-donating group in pyridine and electron-withdrawing group in phenyl acetate, ϱ_x (X;substituents in phenyl ring) values increase gradually according to the electron-donating ability in pyridine substituents, but the |ϱ_y|(Y;substituents in pyridine ring) values decrease with that of substituents. The β values increase with increasing electron-withdrawing ability of the substituents in the phenyl ring, it can be inferred that N---C bond formation increases progressively p-methyl to p-nitrophenyl acetates. This is in agreement with prediction of substituent effects for a simple S_N2 displacement reaction. The sensitivity parameters, β and ϱ, are inter-related and are themselves sensitive to the reactivity of the system. All above results are interpreted in terms of a dissociative S_N2 mechanism involving a metastable tetrahedral intermediate.     

13C NMR spectra of adamantane derivatives

The carbon-13 chemical shifts of mono- and 1,3-disubstituted adamantanes are reported. The effects caused by the substituents are compared with those met in aliphatic and alicyclic compounds. It is shown that the 1,4-interactions have only minor importance in l-substituted adamantanes. The influence of polar groups on the chemical shifts of γ- and δ-carbon atoms is a typical ‘through-the-bonds’ interaction and correlates with inductive parameters of the substituents.     

取代基物化参数及其在药物定量构效关系中的应用

把取代基电性、立体及疏水性物化参数组合建立一种新取代基描述方法, 对环尿素类和N,N-二甲基-2-溴苯乙胺类衍生物进行结构表征. 对训练样本集通过逐步回归筛选变量, 所建多元线性回归方程R2分别为0.853和0.960, 留一法交互检验Rcv2分别为0.723和0.901；用预测集样本作外部预测, 所得Qext2分别为0.7617和0.7653. 结果显示：环尿素类化合物结构中苯环邻位立体、间位疏水、对位疏水及立体因素对该类药物抗HIV活性产生阻抑作用； N,N-二甲基-2-溴苯乙胺类苯环上取代基立体因素及对位给电子效应有利于提高肾上腺素能阻断活性.     

1-芳基-1，4二氢-3芳酰肼基甲酰基-6甲基-4-哒嗪酮的合成及对黄瓜子叶生根作用的构效关系研究

合成了一系列的1-芳基-1，4-二氢-3-芳酰肼基甲酰基-各甲基斗哒嗪酮类化合 物，并用离体黄瓜子叶生根法测试其生物活性，生测结果表明，所有的化合物均显 示出一定的生物活性，并且芳环上的取代基对活性有重要影响．采用化合物的物理 化学参数及化合物促进黄瓜子叶生根的活性，进行了结构与活性定量关系研究，建 立了较好的结构与活性的相关式，化合物的亲脂性和取代基的电性对化合物的生物 活性具有重要的影响．研究结果对3-芳酰肼基甲酰基斗哒嗪酮类化合物的改性或新 类似物的合成具有指导意义．     

Phosphorus–nitrogen rotation barriers: Further studies

Phosphorus–nitrogen rotation barriers have been determined by low temperature NMR methods in a variety of compounds of the type RP(X)NR₂′. The observed activation parameters are concentration and solvent independent. Increasing the bulk of substituents on nitrogen increases the barrier. Phosphonamidous fluorides (X = F) have lower barriers than the corresponding chlorides (X = Cl). Increasing the bulk of substituents on phosphorus decreases the barrier.     

On The Steric Hindrance of Bulky Substituents – Determination of Their Cone Angles

A series of simple halogen compounds was studied with respect to steric hindrance by means of quantum mechanical methods utilizing the M062X/aug‐cc‐pvdz level of theory. The maximal cone angles of the halogen compounds R–E were computed for a series of different substituents (R carbon or silyl based substituents, E = halogen). Depending on the substitution pattern and the bulkiness of the substituent R a correlation between the cone angle and structural parameters is discussed. Estimates for the cone angles of any element attached to R are provided, that allows comparison of cone angles of different substituents at different distances, which can facilitate synthesis. Additionally, the bonding situation was assessed by natural bond orbital (NBO) analysis indicating that significant electronic effects should be considered when changing from silyl to carbon based substituents. Silyl based substituents display a considerably larger charge transfer to E compared to carbon based once.     

Effects of bay substituents on the racemization barriers of perylene bisimides: resolution of atropo-enantiomers

The activation parameters for the interconversion of atropisomers (P- and M-enantiomer) of core-twisted perylene bisimides have been determined by dynamic NMR spectroscopy (DNMR) and time- and temperature-dependent CD spectroscopy. By comparing the activation parameters of a series of perylene bisimides containing halogen or aryloxy substituents in the bay area (1,6,7,12-positions), a clear structure-property relationship has been found that demonstrates that the kinetic and thermodynamic parameters for the inversion of enantiomers are dependent on the apparent overlap parameter Sigmar* of the bay substituents. This study reveals a high stability (DeltaG(368 K) = 118 kJ/mol) for the atropo-enantiomers of tetrabromo-substituted perylene bisimide in solution. Accordingly, the enantiomers of this derivative could be resolved by HPLC on a chiral column. These enantiomers do not racemize in solution at room temperature and, thus, represent the first examples of enantiomerically pure core-twisted perylene bisimides.     

Carbon-13 chemical shifts of monosubstituted cyclohexanes

The carbon-13 chemical shifts of monosubstituted cyclohexane derivatives are compared with those of aliphatic compounds. The polar substituents exert a similar influence on the α-, β- and γ-carbons in both series of compounds. The δ-effect is shown to be characteristic mainly to the cyclic compounds, however. The appearance of a δ-effect is discussed as a possible consequence of electron delocalization in alicyclic molecules. A correlation of these δ-effects with inductive parameters of the substituents is presented.