Effect of molecular structure on dehydrogenation kinetics in the case of C4 and C8 alcohols

Summary The relative adsorption coefficients of ketones are independent of chain length and increase greatly with increased branching of the chain.We express our thanks to A. P. Meshcheryakov for the presentation of 2-ethylhexanol.     

Influence of molecular organization of an azido alcohol solution on the urethane formation kinetics

The quantitative data on the influence of molecular organization of CH₂Cl₂ solutions of diazidopropanol and its non-azide analog (isopropanol) and the concentrations of the alcohols and catalyst (dibutyltin dilaurinate) on the kinetics of urethane formation via the reaction with 1,6-hexamethylene diisocyanate were obtained. The series of reactivity were composed for various associates of hydroxyl groups of these alcohols in solutions in the catalytic and non-catalytic reactions.     

Effect of molecular structure on dehydrogenation in the case of C2 and C25-C9 alcohols

Summary The relative adsorption coefficients of aldehydes are a function of temperature: They fall with rise of temperature. To a first approximation, they do not depend on the chain length.     

Note on the kinetics of dehydrogenation of cyclohexane

Kinetic data available for Pt and Ni suggest doubts about the acceptance of the method applied by V.I. Anikeev et al. [1] as basis for Kinetic Laws for cyclohexane dehydrogenation on Pd/C catalysts.

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Pt Ni , . . . [1] Pd/C.

     

A cobalt redox switch driving alcohol dehydrogenation by redox coupled molecular swing

Developing redox switches that not only perform specific mechanical movements but also drive important chemical reactions is important but a great challenge. Herein, we report a redox pair of cobalt species (Co^III/Co^II) that switches through photo-dehydrogenation of alcohol and hydrogenation of azo-ligand. The cobalt species is equipped with a flexible azo-ligand containing two bulky planar substituents. A planar oxidated sate (Co^III species) can be photo-reduced to a saddle-like reduced state (Co^II) with alcohol molecules as electron donors, and in turn the Co^III species can be recovered with azo-ligand as oxidant under acidic surrounding. Both the redox states of the pair are isolated and characterized by single crystal X-ray diffraction. In the switching cycle, alcohol is oxidized to aldehyde by azo-ligand through proton coupled electron transfer and the cobalt complex acts as a redox catalyst. These results provide important insights into alcohol dehydrogenation catalyzed by redox complexes.     

Crystal and molecular structure of the sesquiterpene humulane alcohol juniferol

The spatial structure of the sesquiterpene humulane alcohol juniferol, which is represented in the crystal by two conformers, IA and IB, differing by the conformation of the C2...C9 section, has been established by the x-ray structural method. The strain energies of the conformers have been calculated by the method of molecular mechanics. The barrier to the interconversion of the conformers by rotation of the C2...C9 section has been calculated; it amounts to 7–8 kcal/mole. This value of the transformation barrier permits the assumption that the two conformers also exist in solution, their interconversion being hindered. Institute of Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Institute of Crystallography, Academy of Sciences of the USSR, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 757–762, November–December, 1990.     

Crystal and molecular structure of the sesquiterpene humulane alcohol juniferol

The spatial structure of the sesquiterpene humulane alcohol juniferol, which is represented in the crystal by two conformers, IA and IB, differing by the conformation of the C2...C9 section, has been established by the x-ray structural method. The strain energies of the conformers have been calculated by the method of molecular mechanics. The barrier to the interconversion of the conformers by rotation of the C2...C9 section has been calculated; it amounts to 7–8 kcal/mole. This value of the transformation barrier permits the assumption that the two conformers also exist in solution, their interconversion being hindered.Institute of Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Institute of Crystallography, Academy of Sciences of the USSR, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 757–762, November–December, 1990.     

Effect of the catalyst structure on the catalytic activity in dehydrogenation of 2-methyl butane

Calorimetry, thermogravimetry, X-ray diffraction analysis, and low-temperature adsorption of nitrogen were used to study the structure of bimetallic Pt—Sn catalysts on zinc–alumina spinel supports. The effect of the porous structure of the catalyst samples synthesized on their catalytic activity in dehydrogenation of 2–methyl butane was analyzed.     

Effect of structure of the redox molecular sieve TS-1 on the oxidation of phenol, crotyl alcohol and norbornylene

A range of crystalline TS-1 samples with different morphologies as well as the corresponding TS-1 precursor structures have been synthesised using hydrothermal crystallisation. The materials have been characterised using powder X-ray diffraction, IR and Raman spectroscopy and electron microscopy. The materials were used as catalysts for the oxidation of crotyl alcohol, phenol and norbornylene and, in particular, the reactivity of the precursor structures was contrasted with crystalline TS-1. The oxidation of crotyl alcohol, selected as a relatively non-reactive substituted alkene, did not require the TS-1 structure for reactivity and TS-1 precursor structures are active, although crystalline TS-1 was found to be more reactive than the precursor structures. In contrast, phenol hydroxylation is only catalysed by crystalline TS-1. The reaction of phenol is observed to occur only on the exterior surface of large TS-1 crystallites. With smaller crystallites of TS-1, i.e. the size range of interest for catalysis, the rapid subsequent reaction of hydroquinone makes it difficult to determine whether reaction occurs solely on the exterior of the crystallites or at sites within the porous structure. Hence it is suggested that this reaction has limited scope as a probe reaction for the reactivity of sites within the crystallites. It is, however, feasible that phenol hydroxylation is a viable probe reaction for TS-1 type structural units. Norbornylene was studied as an example of a reactant too large to enter the internal pore structure of TS-1 and hence only reaction at pore mouths and external surface sites was possible. Larger TS-1 crystallites were more active for this substrate than suggested by surface area considerations. The results are discussed in terms of the selection of model reactions for the study of TS-1 catalysts.     

Effect of molecular structure on the crystal-nematic phase transition

A systematic study of the crystal-nematic phase transition for a series of unsymmetricalp-phenylene bis (p-substituted benzoates) is reported. Differences in molecular structure along the series are in the nature of one small, compact terminal substituent. Enthalpy and entropy measurements are reported for the crystal-nematic transition as obtained by differential thermal analysis. A correlation between the thermodynamic data and molecular structure is presented.

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Zusammenfassung Eine systematische Untersuchung über den kristallin-nematischen Phasenübergang einer Reihe asymmetrischerp-Phenylen-bis-(p-substituierter Benzoate) wird bekanntgegeben. Die Unterschiede der Molekularstruktur der Serienglieder bestehen in der Beschaffenheit eines kleinen, kompakten, terminalen Substituenten. Die mittels Differentialthermoanalyse erhaltenen Enthalpie- und Entropiemessungen des kristallin-nematischen Überganges werden beschrieben. Eine Korrelation zwischen den thermodynamischen Daten und der Molekularstruktur wird gegeben.

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Résumé On communique les résultats d'une étude systématique de la transition de phase entre l'état cristallin et l'état nématique d'une série de benzoatesp-phénylène bisp-substitués asymétriques. Les différences de structure moléculaire des membres de la série sont dues à la nature d'un substituant terminal compact de faible dimension. On décrit les mesures d'enthalpie et d'entropie de la transition entre l'état cristallin et l'état nématique, effectuées par ATD. On présente une corrélation entre les données thermodynamiques et la structure moléculaire.

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