Molecular mass distribution of aliphatic and aromatic hydrocarbons obtained from CO and H2 in the presence of Fe catalysts

It has been demonstrated that together with C₁-C₆ aliphatic hydrocarbons up to 20% C₆-C₉ aromatic hydrocarbons are formed from a mixture of COH₂ (11) in the presence of 8.2% Fe-4.5% K/Al₂O₃. A new method for determining the parameter a in the Schultz-Flory equation has been proposed which is applicable to the synthesis of low molecular mass C₁-C₆ hydrocarbons. It has been shown that the mass fractions of aromatic hydrocarbons are higher than the values expected on the basis of a step-wise mechanism for growth of the hydrocarbon chain.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 40–44, January, 1991.     

Influence of preliminary treatment on activity and selectivity of Co-alumosilicate catalyst in hydrocarbon synthesis from CO and H2

The temperature and medium of preliminary treatment of 10% Co/SiO ₂·Al₂O₃ influence the activity and selectivity in hydrocarbon synthesis from CO and H₂. Treatment with NH₃ reduces the yield. Increasing the treatment temperature leads to a loss of activity and a change in the composition of hydrocarbons formed. The reason for deactivation is a change in the catalyst surface texture, its adsorptive properties, and the ability to be reduced.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1709–1713, August, 1990.     

High-pressure synthesis of carbamates by the carbonylation of aromatic nitro compounds in cyclohexanol

A study was carried out on the high-pressure carbonylation of nitrobenzene and 3-chloronitrobenzene by CO in cyclohexanol in the presence of PdCl₂-FeCl₃-pyridine with the formation of cyclohexyl-N-phenylcarbamate and cyclohexyl-N-3-chlorophenylcarbamate in 90–95% yield and nitro compound conversion of 95–99%. The feasibility of the repeated use of this catalyst was demonstrated.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1885–1887, August, 1991.     

The Feynman-Kac formula with a Lebesgue-Stieltjes measure: An integral equation in the general case

Let u(t) be the operator associated by path integration with the Feynman-Kac functional in which the time integration is performed with respect to an arbitrary Borel measure instead of ordinary Lebesgue measurel. We show that u(t), considered as a function of time t, satisfies a Volterra-Stieltjes integral equation, denoted by (*). We refer to this result as the Feynman-Kac formula with a Lebesgue-Stieltjes measure. Indeed, when n=l, we recover the classical Feynman-Kac formula since (*) then yields the heat (resp., Schrödinger) equation in the diffusion (resp., quantum mechanical) case. We stress that the measure is in general the sum of an absolutely continuous, a singular continuous and a (countably supported) discrete part. We also study various properties of (*) and of its solution. These results extend and use previous work of the author dealing with measures having finitely supported discrete part (Stud. Appl. Math.76 (1987), 93–132); they seem to be new in the diffusion (or imaginary time) as well as in the quantum mechanical (or real time) case.Research partially supported by the National Science Foundation under Grant DMS 8703138. This work was also supported in part by NSF Grant 8120790 at the Mathematical Sciences Research Institute in Berkeley, U.S.A., the CNPq and the Organization of Latin American States at theInstituto de Matemática Pura E Aplicada (IMPA) in Rio de Janeiro, Brazil, as well as theUniversité Pierre et Marie Curie (Paris VI) and the Université Paris Dauphine in Paris, France.     

Characteristics of the catalytic action of Co systems in the synthesis of hydrocarbons from Co and H2

Conclusions On the basis of experimental data, assumptions have been made concerning the possibility of prediction of the properties of Co catalysts for the synthesis of hydrocarbons from carbon monoxide and hydrogen with due regard for the properties of the supports, the nature of the thermodesorption of CO from the surface of the catalyst, and the method of its preparation.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 60–66, January, 1984.     

Computer-aided determination of relative stereochemistry and 3D models of complex organic molecules from 2D NMR spectra

A method for elucidation of the relative stereoconfiguration of natural product molecular structures and their 3D models based on NOE data and the application of a genetic algorithm is described. The method is applicable mainly for rigid polycyclic structures commonly encountered in natural products. It is demonstrated that the technique of simulated annealing cannot be easily used when dealing with low-weight fused ring molecules but the application of a genetic algorithm is proven successful. Examples of a typical genetic algorithm workflow and the optimization of the algorithmic parameters are discussed. The efficiency of the approach developed here is demonstrated on the complex natural products of both Taxol^® (C₄₇H₅₁NO₁₄) and brevetoxin B (C₅₀H₇₀O₁₄).     

Structure elucidation from 2D NMR spectra using the StrucEluc expert system: detection and removal of contradictions in the data

The elucidation of chemical structures from 2D NMR data commonly utilizes a combination of COSY, HMQC/HSQC, and HMBC data. Generally COSY connectivities are assumed to mostly describe the separation of protons that are separated by 1 skeletal bond (3JHH), while HMBC connectivities represent protons separated from carbon atoms by 1 to 2 skeletal bonds (2JCH and 3JCH). Obviously COSY and HMBC connectivities of lengths greater than those described have been detected. Though experimental techniques have recently been described to aid in the identification of the nature of the couplings the detection of whether a coupling is 2-bond or greater still remains a challenge in most laboratories. In the StrucEluc software system the common lengths of the connectivities, 1-bond for COSY and 1- or 2-bond for HMBC, derived from 2D NMR data are set as the default. Therefore, in the presence of any extended connectivities contradictions can appear in the 2D NMR data. In this article, algorithmic methods for the detection and removal of contradictions in 2D NMR data that have been developed in support of StrucEluc are described. The methods are based on the analysis of molecular connectivity diagrams, MCDs. These methods have been implemented in the StrucEluc system and tested by solving 50 structural problems with 2D NMR spectral data containing contradictions. The presence of contradictions was detected by the algorithm in 90% of the cases, and the contradictions were automatically removed in approximately 50% of the problems. A method of "fuzzy" structure generation in the presence of contradictions has been suggested and successfully tested in this work. This work will demonstrate examples of the application of developed methods to a number of structural problems.     

The problem of joint optimization of product parameters and statistical quality control plans using a quantitative index

We solve the problem of joint optimization of quality assurane and choice of a quality control plan using a quantitative index for the case of normally distributed quality parameters. Some estimates of the efficiency of the proposed approach compared with the classical method are given.Translated from Statisticheskie Metody pp. 80–97, 1982.     

Automated structure elucidation — the benefits of a symbiotic relationship between the spectroscopist and the expert system

Characteristic features of a new expert system StrucEluc are described. The system is intended for the structure elucidation of complex organic molecules using a variety of spectroscopic data including 2D NMR. We review here the results of challenging this system with over 100 structure elucidation problems where the 2D NMR peak tables presented in original journal publications provided the input data. This contribution is focused on methods to overcome difficult situations that can arise when contradictions are present in the input data and/or when the structure is underdetermined as a result of insufficient 2D NMR correlations. Methods by which to address these situations are examined. It has been shown that synergy between the spectroscopist and the expert system allows the solution of problems that seemed to be hopeless at the outset of the structure elucidation process.