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Showing papers in "ChemInform in 1978"


Journal ArticleDOI
Abstract: (11) Potassium ferricyanide has previously been used to convert w'c-1,2-dicarboxylate groups to double bonds. See, for example, L. F. Fieser and M. J. Haddadln, J. Am. Chem. Soc., 86, 2392 (1964). The oxidative dldecarboxylation of 1,2-dlcarboxyllc acids is, of course, a well-known process. See Inter alia (a) C. A. Grob, M. Ohta, and A. Weiss, Helv. Chim. Acta, 41, 1911 (1958); and (b) E. N. Cain, R. Vukov, and S. Masamune, J. Chem. Soc. D, 98 (1969).

4,709 citations



Journal ArticleDOI

423 citations






Journal ArticleDOI
TL;DR: In this article, the stability constants of ferric complexes with several substituted catechol (1,2-dihydroxybenzene) ligands in aqueous solutions of low ionic strength have been determined at 27/sup 0/C in the pH range 2 to 11.
Abstract: The stability constants of ferric complexes with several substituted catechol (1,2-dihydroxybenzene) ligands in aqueous solutions of low ionic strength have been determined at 27/sup 0/C in the pH range 2 to 11. Enterobactin, the principal siderophore of enteric bacteria, is a tricatechol and, from the formation constants reported here, is estimated to have a formation constant with ferric ion which is greater than 10/sup 45/. The stepwise formation constants, K/sub n/, of the catechol ligands reported here are defined as (ML/sub n/)/(ML/sub n-1/)(L), in units of L mol/sup -1/, where (L) is the concentration of the deprotonated catechol ligand. The constants were determined from potentiometric and spectroscopic data and were refined on pH values by weighted least squares. Qualitative examination of electron spin resonance spectra of the systems indicated some oxidation of the ligand by ferric ions at pH values as high as 4. The ligands studied included catechol (cat) (log K/sub 1/ = 20.01, log K/sub 2/ = 14.69, log K/sub 3/ = 9.01); 4,5-dihydroxy-m-benzenedisulfonate (Tiron) (log K/sub 2/ = 15.12, log K/sub 3/ = 10.10); 4-nitrocatechol (ncat) (log K/sub 1/ = 17.08, log K/sub 2/ = 13.43, log K/sub 3/ = 9.51); 3,4-dihydroxyphenylacetic acid (dhpa) (log K/sub 1/more » = 20.1, log K/sub 2/ = 14.9, log K/sub 3/ = 9.0); and 2,3-dihydroxybenzoic acid (dhba) (log K/sub 1/ = 20.5). The acid dissociation constants, K/sub a/s, were determined also. For the catechol protons these follow: cat (pK/sub a/sub 1// = 9.22, pK/sub a/sub 2// = 13.0); Tiron (pK/sub a/sub 1// = 7.70, pK/sub a/sub 2// = 12.63); ncat (pK/sub a/sub 1// = 6.65, pK/sub a/sub 2// = 10.80); dhpa (pK/sub a/sub 1// = 9.49, pK/sub a/sub 2// = 13.7); and dhba (pK/sub a/sub 1// = 10.06, pK/sub a/sub 2// = 13.1). In addition, carboxylate substituents of dhpa and dhba have pK/sub a/s of 4.17 and 2.70, respectively.In solution, exchange is slow between these two types of coordination following changes in pH. 2 tables, 11 figures, 52 references.« less

276 citations



Journal ArticleDOI
TL;DR: In this article, the effects of halogenated solvents such as n-butyl chloride, n-propyl bromide, and ethyl iodide on the photochemistry of several aromatic compounds are reviewed.
Abstract: The effects of halogenated solvents such as n-butyl chloride, n-propyl bromide, and ethyl iodide, on the photochemistry of several aromatic compounds are reviewed. Dimerization of acenaphthylene is discussed in terms of spin -orbit coupling induced by the solvents. Appropriate wave functions are given for both the solvents and the compound. Cycloaddition reactions, electrocyclic rearrangements, and photochemical cis-trans isomerization are also considered.

244 citations


Journal ArticleDOI
TL;DR: In this article, the properties of both amorphous and crystalline salts of tetravalent metals are reviewed, with special emphasis on the much studied salt of zirconium phosphate.
Abstract: Properties of both amorphous and crystalline salts of tetravalent metals are reviewed, with special emphasis on the much studied salt of zirconium phosphate. The discussion includes: (1) method of preparation, (2) interlayered crystal structure, (3) effect of counter ions on interlayer distance and steric hindrance, (4) mechanism of ion exchange, and (5) the interaction of polar molecules. Other insoluble acid salts with a layered structure include the phosphates of titanium, hafnium, germanium, tin, lead, and the arsenates of titanium, zirconium, and tin. Fibrous precipitates of the insoluble acid salts of cesium and thorium phosphate are mentioned briefly. Under appropriate experimental conditions, insoluble acid of unknown structure can be obtained. Investigations of their crystalline structure may be highly desirable. The ion exchange capacities of many of these substances are evaluated. 80 references, 3 tables, 4 figures.

Journal ArticleDOI
TL;DR: The p-Bromphenol (I) reagiert mit dem Acrylester (II) in Gegenwart von Phosphinen (III) und Palladium(II)-acetat zum p-Hydroxy-zimtsaureester (IV) as mentioned in this paper.
Abstract: p-Bromphenol (I) reagiert mit dem Acrylester (II) in Gegenwart von Phosphinen (III) und Palladium(II)-acetat zum p-Hydroxy-zimtsaureester (IV).

Journal ArticleDOI
TL;DR: The use of phosphorus compounds as catalysts has also accelerated in the last decade as mentioned in this paper, and it is not unexpected, then, to find that the use of compounds of phosphorus can also accelerate the development of catalysts.
Abstract: Although carbon is often considered as the dominant element in terms of covalent bond formation, phosphorus can undoubtedly be considered a s a serious competitor for this position [1]. Further, at least in principle, phosphorus is potentially capable of forming more compounds than carbon. For a variety of reasons, both academic and practical, interest in phosphorus compounds has increased markedly over the last decade. It is not unexpected, then, to find that the use of compounds of phosphorus as catalysts has also accelerated. Unfortunately, a s is often the case in science, the practice outruns the theory with such catalysts, but industrialists and academicians alike have recently displayed an enhanced interest in the mechanisms of catalytic activity on such catalysts.


Journal ArticleDOI
TL;DR: In this paper, a discussion of catalysis by supported catalysts that are liquid at reaction temperature covers the preparation, composition, and structure of copper chloride-based Deacon catalysts used, e.g., for the oxychlorination of ethylene; alkali-promoted vanadium catalysts for sulfur dioxide oxidation in sulfuric acid manufacturing; kieselguhr-supported phosphoric acid used in the oligomerization of alkenes and alkylation of aromatics for gasoline and polymer production and in the hydration of alcohols.
Abstract: A discussion of catalysis by supported catalysts that are liquid at reaction temperature covers the preparation, composition, and structure of copper chloride-based Deacon catalysts used, e.g., for the oxychlorination of ethylene; alkali-promoted vanadium catalysts for sulfur dioxide oxidation in sulfuric acid manufacturing; kieselguhr-supported phosphoric acid used in the oligomerization of alkenes and alkylation of aromatics for gasoline and polymer production and in the hydration of alkenes to alcohols; and theoretical aspects of supported liquid catalysts, including mechanism of adsorption and models of the distribution of the liquid on the support, the effects of diffusion and loading on the reaction kinetics, effective diffusion coefficients; and diffusion and reaction in the liquid phase.




Journal ArticleDOI
TL;DR: In this paper, a methodology for the study of the influence of crystal forces on molecular conformation has been developed and ap- plied, where a combination of quantitative analysis of the molecular pack- ing in different space groups along with ab initio molecular orbital calculations is used to analyze these phenomena.
Abstract: A methodology for the study of the influence of crystal forces on molecular conformation has been developed and ap- plied. As part of this study the phenomenon of conformationalpolymorphism, in which a molecule adopts significantly differ- ent conformations in different crystal polymorphs, is elucidated. A combination of quantitative analysis of the molecular pack- ing in different space groups along with ab initio molecular orbital calculations is used to analyze these phenomena. The model system p-(N-chlorobenzy1idene)-p-chloroaniline (a Schiff base) was chosen for study. Lattice energy calculations involving the minimization of the energy of the triclinic and orthorhombic crystal forms of this molecule were carried out in order to ex- plain the stability of the former lattice in which the unstable planar conformation of the molecule obtains. Three different po- tential functions were employed (6-9, 6- 12, and 6-exp), in order to avoid "potential-dependent" conclusions. All potentials yielded lower energies (more negative), for the triclinic lattice, in agreement with the experimental observation. The conforma- tional energy of the isolated molecule was studied by molecular orbital methods using both minimal and split valance basis sets. The energy differences obtained from these calculations are in good agreement with the differences in lattice energies obtained from the crystal calculations. A "partitioning" of the lattice energy into "partial atomic energies" was performed in order to carry out a detailed analysis of the packing differences between the polymorphs. The introduction of this partitioning proved to be a powerful probe for analyses of the energetics of different crystal packing modes. The approach employed, including packing analysis and crystal energetic studies to conformational polymorphs, yields much information as to the nature of the crystal forces in the different polymorphs and promises to be a useful tool in the investigation of the role of these forces in in- fluencing molecular conformation.


Journal ArticleDOI
TL;DR: In this article, selfoscillation processes were used to study the regularities of a reaction medium with a catalytic surface under norrsteady-state conditions operating for a longer time.
Abstract: The dynamics of a chemical system is thc main characteristic of the system. An attracrivc problem of the dynamics pertains to selfoscillation processes. These processes are promising for a study of regularities tnttetant in the Lmemctioa of a reaction medium wttfi a catalytic surface under norrsteady-state conditions operating for a longer time.



Book ChapterDOI
TL;DR: In this paper, the main electronic and steric factors of heteroaromatic nucleophilic reactants that influence their reactivity are discussed, as well as recent important developments dealing with quaternization of annular nitrogen atoms of heterocyclic compounds.
Abstract: Publisher Summary This chapter focuses on important developments dealing with quaternization of annular nitrogen atoms of heterocyclic compounds The chapter is essentially divided into two main parts The first part describes the main electronic and steric factors of heteroaromatic nucleophilic reactants that influence their reactivity The second part provides references to recent important developments The chapter considers six-membered heteroaromatic rings before five-membered ones as the six-membered rings are studied in greater detail and consequently their reactions are better understood The chapter notes that quaternization of an annular nitrogen atom is carried out with a wide range of alkylating agents Most quaternization reactions involving an annular nitrogen atom and an alkylating agent proceed by way of an S N 2 reaction in which the inversion of configuration of a chiral reagent takes place One novel method, which indicates that the transition state is early, involves the study of volume changes Many approaches are made to obtain information about the nature of the transition state of quaternization reactions, including a study of kinetic isotope effects

Book ChapterDOI
TL;DR: In this paper, a computer program is developed which automatically generates sequences of chemical reactions, all conceivable reactions are obtained irrespective of whether they are already known or are without precedence, and this program is especially useful for planning organic syntheses and generating the products of starting materials.
Abstract: A computer program has been developed which automatically generates sequences of chemical reactions. As reactions are treated quite formally, all conceivable reactions are obtained irrespective of whether they axe already known or are without precedence. This program is especially useful for planning organic syntheses and fox generating the products of starting materials. The system is in very active development but the present version can already serve as a tool for the chemist in studying problems of immediate interest. Examples for applications are given to demonstrate the flexibility and performance of the program.



Journal ArticleDOI
TL;DR: In this paper, the Synthese des aminosubstituierten Triarylphosphin-Liganden Tris-[p-(aminomethyl)-phenyl]-phophosphin, der als Tris-tosylat (IV) nach dem aufgezeigten Schema ausgehend von dem Diacetal (I) gebildet und isoliert wird, ermoglicht die Darstellung der wasserloslichen Undecagold-Cluster (V
Abstract: Die Synthese des aminosubstituierten Triarylphosphin-Liganden Tris-[p-(aminomethyl)-phenyl]-phosphin, der als Tris-tosylat (IV) nach dem aufgezeigten Schema ausgehend von dem Diacetal (I) gebildet und isoliert wird, ermoglicht die Darstellung der wasserloslichen Undecagold-Cluster (VIII).


Journal ArticleDOI
TL;DR: Diaryliodoniumsalze (I) reagieren mit Diphenylsulfid (II) zu den gemischten Triarylsulfonium-Salzen (III).
Abstract: Diaryliodoniumsalze (I) reagieren mit Diphenylsulfid (II) zu den gemischten Triarylsulfonium-Salzen (III).