Empirical procedure for the calculation of ionization constants of organic compounds in water from their molecular volume

An empirical procedure was used to calculate 278 ionization constants of 271 organic compounds, including phenols, NH acids, benzoic acid derivatives, and mono- and dihydric carboxylic acids, in water. The examined compounds were divided into 11 structural groups. The ionization constants for compounds belonging to a single group were calculated from constant empirical coefficients, molecular volumes, and formulas with an average error of less than 3.5%, the maximal error not exceeding 9.9%.     

Supported Zr-and Hf-cene Catalysts for Propylene Polymerization

The supported metallocene catalysts were obtained on the layered silicate montmorillonite (MMT), using AlMe₃ and AliBu₃ for synthesis of alkylaluminoxane directly on a support surface, followed by metallocene supporting. It was shown that the MMT-H₂O/AliBu₃ forms with ansa-Zr-cenes of C₁ and C₂-symmetry the significantly more active supported metal-alkyl complexes in propene polymerization, than MMT-H₂O/AlMe₃. The MMT-H₂O/AliBu₃ is the effective activator of the ansa-Hf-cenes, in contrast to MAO and MMT-H₂O/AlMe₃, giving the high active supported catalysts for synthesis of isotactic and elastic polypropene. The character of influence of metallocene fixation on support on the isotactic pentad [mmmm] content in polymer, compared to homogeneous analogues, depends on the metallocene nature. The introduction of borate Ph₃CB(C₆F₅)₄ in the case of both Zr-cene and Hf-cene catalysts increases significantly the activity at the reduced ratio of Al/Zr, Hf (100–500 instead of 2000–3000) and stabilizes the catalytic complexes.     

Investigation of azlactones and azlactams by IR spectroscopy

The IR spectra of a number of azlactones and their structural analogs, viz., azlactams, in solutions in carbon tetrachloride and in chloroform and in the solid phase were obtained. The character of the interaction of the carbonyl group of the heteroring with substituents with different electronic natures has a substantial effect on the frequencies of the stretching vibrations of the carbonyl group and the azomethine and ethylene bonds. The carbonyl frequencies were subjected to correlation analysis, and high conductivity of the electronic effects of substituents in the 2-phenyl-4-arylideneoxazol-5-one series was ascertained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 171–174, February, 1984.     

Magnetic resonance imaging methods for in situ studies in heterogeneous catalysis

Magnetic resonance imaging (MRI) is a very powerful instrument used extensively in modern medical diagnostics because of its ability to look inside a body in a non-invasive and non-destructive way. Furthermore, MRI is more than just a single tool for extracting structural information. It is more of a sophisticated and versatile toolkit able to provide all sorts of useful information about the internal properties of an object under study and various processes within it, including heat and mass transport, composition and chemical transformations, in a spatially resolved mode. While a living body is different from a catalyst body or a reactor, the in situ and Operando studies in catalysis can clearly benefit from the use of this non-destructive toolkit as a powerful complement to other available spectroscopic tools. This tutorial review gives an introduction to the field and describes the examples of the applications of MRI to the studies of the preparation, deactivation and regeneration of solid catalysts and to the spectroscopy, thermometry and imaging studies of heterogeneous catalysts and model catalytic reactors performed during actual catalytic processes.     

流体力学半径对估算胶体微球聚集速率常数的影响

胶体粒子聚集速率常数实验值远低于理论值一直是被普遍关注的问题.聚集速率常数的理论推导是基于粒子的几何半径来考虑的,但决定粒子扩散速率及聚集速率的应该是粒子的流体力学半径(大于几何半径),因而它是使聚集速率常数实验值低于理论值的因素之一.影响流体力学半径的因素很多,其中,带电粒子在溶液中因表面存在双电层,会明显增大流体力学半径,造成聚集速率减慢.而双电层的厚度又随溶液中离子强度的不同而改变.本工作在聚集速率的公式中引入了修正因子,即几何半径与其流体力学半径之比,以修正由于用几何半径代替流体力学半径带来的误差.其中几何半径和流体力学半径可以分别用扫描电镜(SEM)和动态光散射(DLS)来测定.以两种粒径的聚苯乙烯带电微球为例,考察了在不同离子强度下,该误差的大小.结果发现,对于半径为30 nm的微球,用流体力学半径计算的慢聚集速率常数比理论值偏低约8%.该误差随离子强度增加而减少.对于快聚集情况,流体力学半径对聚集速率基本没有影响.     

Multinuclear magnetic resonance imaging in catalytic research: Recent advances and future prospects

The most important applications of magnetic resonance imaging in catalysis and related areas are considered. In combination with other advanced instrumental methods, this technique can provide essential information about the properties of catalysts and reactors and about processes occurring there. The examples given in the report include the preparation and characterization of porous supports; loading of supports with an active component by impregnation; and investigation of the structure of a granular catalyst bed, various mass transfer processes, and the operation dynamics of a model reactor.     

Spectrophotometric determination of ionization constants of some organic compounds in aqueous solution

Ionization constants of some phenols and anilines in aqueous solution with a ionic strength of 0.01 were measured at 25°C by spectrophotometric method. The set of substrates was selected on the basis of the results of preliminary calculations of ionization constants in terms of an elemental linear empirical approach with account taken of the lack of the corresponding consistent published data.