Composition catalysts of ethylbenzene oxidation based on bis(acetylacetonato)nickel(ii) and phase transfer catalysts as ligands 1. Macrocyclic polyethers

The addition of the macrocyclic polyether 18-Crown-6 (18C6) increases the selectivity of oxidation of ethylbenzene to -phenylethylhydroperoxide (PEH) in the presence of Ni(acac)₂. The initial oxidation rate, selectivity and degree of conversion of ethylbenzene to PEH are greater than those catalyzed by Ni(acac)₂ only. The efficiency of the macrocyclic ligand as an activator of Ni(acac)₂ exceeds that of monodentate donor ligands. The high selectivity of the process is due to both the primary Ni(acac)₂ · 18C6 complexes and the products of their transformation in the course of oxidation. The mechanism of ethylbenzene oxidation catalyzed by Ni(acac)₂ · 18C6 complexes is discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1406–1411, August, 1994.     

Plasmids from thermophilicClostridia

Applied Biochemistry and Biotechnology - Thus, since the first publication (1987) on the detection of plasmids in thermophilic Clostridia, nearly 10 of their cryptic plasmids have been discovered....     

Selective oxidation of ethylbenzene by dioxygen. The effect of chelate center on catalysis by bicyclic nickel complexes

The effect of the nature of the chelate center in Ni^II complexes on their catalytic activity in the selective oxidation of ethylbenzene by dioxygen to α-phenylethyl hydroperoxide in the presence of nickel bis(acetylacetonate) (chelate center Ni(O,O)₂) and nickel bis(enaminoacetonate) (chelate center Ni(O,NH)₂) was studied. The efficiency of selective oxidation of ethylbenzene increases substantially in the presence of the chelate with the Ni(O,NH)₂ active center as a catalyst, which is mainly due to the transformation of the catalyst into more active species during the oxidation process. The mechanism of transformation of nickel bis(enaminoacetonate) under the action of dioxygen was suggested. The sequence of formation of the reaction products at different stages of the catalytic process was determined. The activity of the nickel complex with the Ni(O,NH)₂ chelate center and the products of its transformation in the elementary stages of chain oxidation of ethylbenzene is discussed. Translated fromIzvestiya Akedemii Nauk. Seriya Khimicheskaya, No. 1, pp. 55–60, January, 1999.     

Oxidation of Ethylbenzene with Dioxygen in the Presence of Iron(III) Tris(acetylacetonate)-Based Catalytic Systems: 1. Mechanism of Ethylbenzene Oxidation with Dioxygen Catalyzed by Fe(III)(acac)<Subscript>3</Subscript>

The catalytic activity of Fe(III)(acac)₃ (Cat) in ethylbenzene oxidation with dioxygen is studied. 1-Phenylethyl hydroperoxide (PEHP), acetophenone (AP), and methyl phenyl carbinol (MPC) are the main products of the process throughout the Cat concentration range examined. Phenol (Ph) is formed in much smaller amounts. The highest PEHP selectivity, S _PEHP = 65%, is observed at an ethylbenzene conversion of C ≈ 2% at low [Cat] values. PEHP and the other main oxidation products (AP and MPC) form by parallel reactions at any Cat concentration. Depending on [Cat], AP and MPC form by parallel or consecutive reactions. When [Cat] is high enough, AP results from MPC oxidation. At the initial stages of the reaction, the MPC selectivity (S _MPC = 50%) exceeds the PEHP selectivity (S _PEHP = 25–30%). The mechanism of ethylbenzene oxidation catalyzed by Fe(III)(acac)₃ and the role of active complexes in its steps are considered.__________Translated from Kinetika i Kataliz, Vol. 46, No. 3, 2005, pp. 354–359.Original Russian Text Copyright © 2005 by Matienko, Mosolova.     

Selective Oxidation of Ethylbenzene by Molecular Oxygen: Effect of Macrocyclic 18-Crown-6 Polyether Additives on Catalysis by Bicyclic Nickel Complexes

The catalytic activity of the two-component catalytic system based on nickel bis(enaminoacetonate) (enamac) and 18-crown-6 (18C6) macrocyclic polyether is studied in ethylbenzene oxidation by molecular oxygen. The {Ni(enamac)₂ + 18-crown-6} system is a more active catalyst of ethylbenzene oxidation into -phenylethyl hydroperoxide compared to Ni(enamac)₂ and the {Ni(acac)₂ + 18-crown-6} system. The formation of Ni(enamac)₂–18-crown-6 complex is confirmed both kinetically and spectroscopically. It is suggested that a rise in the oxidation selectivity is due to Ni(enamac)₂ transformation activated by 18-crown-6. The order of oxidation product formation at different oxidation stages is determined. The activity of catalysts in the elementary steps of the chain process is discussed.     

New formula for ln(eAeB) in terms of commutators of A and B

We establish the formula $$\ln (e^B e^A ) = \smallint _0^t \psi (e^{ - \tau ad_A } e^{ - \tau ad_B } ) e^{ - \tau ad_A } d\tau (A + B),$$ where Ψ(x)=(In x)/(x ? 1); here A and B are elements of a. finite-dimensional Lie algebra which satisfy certain conditions. This formula enables us, in particular, to give a simple proof of the Campbell-Hausdorff theorem. We also give a generalization of the formula to the case of an arbitrary number of factors.     

Kinetics of growth and metabolism ofClostridium thermosaccharolyticum culture

The kinetics of growth and metabolism of Clostridium thermosaccharolyticum DSM 571 has been studied at varying initial pH and glucose concentration. A weak inhibitory effect of excess glucose on the specific growth rate has been shown. The effect of antibiotics of various classes on culture growth and hydrogen evolution has been studied. Streptomycin and kanamycin resistance of this culture has been revealed as well as the phenomenon of increased hydrogen production in the presence of the above antibiotics. New plasmids, pNB1 (4.9 kb) and pNB2 (2.0 kb), were isolated from C. thermosaccharolyticum DSM 571. The restriction analysis of pNB1 and pNB2 has been performed.     

Conceptual Design of a Dedicated Fourth-Generation Specialized Synchrotron Radiation Source (SSRS-4) at the Kurchatov Institute

Physics of Atomic Nuclei - Work on the conceptual design of a dedicated fourth-generation fourth-generation Specialized Synchrotron Radiation Source (SSRS-4) is in progress at the Kurchatov...