Просмотр исходного текста страницы -This-quantity-makes-contact-with-Zimmermans-alternative-approach-to-the-WH-rules-based-on-the-aromaticity-of-the-transition-state-k

Using the dual descriptor and the initial hardness response, we reinterpret the WH results for the four types of pericyclic reactions (cycloadditions, electrocyclizations, and sigmatropic and chelotropic reactions), both thermodynamically and photochemically. We demonstrate that these two approaches, which require only simple quantum chemical procedures (overlapping densities and HOMO-LUMO gap type calculations along a few points of a model reaction coordinate), are intimately related through a relation that converts the local (i.e., position-dependent) dual descriptor into the global (i.e., position-independent) (initial) hardness response.<br /><br /> Our results show that with a density-only based approach the WH rules can be reinterpreted, pointing to the fundamental importance of the electron density as carrier of information as highlighted in the basic theorems of DFT.A Domino Diels-Alder Approach toward the Tetracyclic Nicandrenone Framework.The tetracarbocyclic framework of the nicandrenone natural products is formed in one step from a linear precursor via a domino intramolecular Diels-Alder/intramolecular furan Diels-Alder/aromatization sequence. The approach represents a new 0 → ABCD strategy for the preparation of aromatic Synthesis of allocolchicines using sequential ring-closing enyne New allocolchinoids having functionality in the C ring at position C10 or C11 have been synthesized using the enyne ring-closing metathesis (RCM) reaction for construction of the seven-membered ring and a Diels-Alder-aromatization sequence for the elaboration of the aromatic ring C. [reaction: see text].Silorane-based dental composite: behavior and abilities.Ludwig-Maximilians-University, Munich, Germany.<br /><br /> The purpose of this study was to examine the characteristics of an innovative composite material for dental restorations based on silorane--a monomer with a new chemical composition, and thereby compare the examined characteristics against those of well-known methacrylate-based composites. [https://dailyuploads.net/vgvzw1wlgyb4 cyanocobalamin salcaprozate sodium] of conversion at 2-mm and 6-mm depths as well as hardness, modulus of elasticity, and creep resistance through the middle of 6-mm high samples were measured. It was observed that up to 20 minutes after curing, curing time--and not irradiance--played the determinant role for a high degree of cure. No differences were registered between the two categories of material in terms of hardness. However, modulus of elasticity of the silorane-based material was slightly lower and the creep resistance higher than a methacrylate composite (Tetric EvoCeram). In conclusion, siloranes exhibited good mechanical properties comparable to those of clinically successful methacrylate-based composite Toward Biorecycling: Isolation of a Soil Bacterium That Grows on a Polyurethane Infection Research - HZI, Braunschweig, Germany.The fate of plastic waste and a sustainable use of synthetic polymers is one of the major challenges of the twenty first century.<br /><br /> Waste valorization strategies can contribute to the solution of this problem. Besides chemical recycling, biological degradation could be a promising tool. Among the high diversity of synthetic polymers, polyurethanes are widely used as foams and insulation materials. In order to examine bacterial biodegradability of polyurethanes, a soil bacterium was isolated from a site rich in brittle plastic waste. The strain, identified as Pseudomonas sp. by 16S rRNA gene sequencing and membrane fatty acid profile, was able to grow on a PU-diol solution, a polyurethane oligomer, as the sole source of carbon and energy. In addition, the strain was able to use 2,4-diaminotoluene, a common precursor and putative degradation intermediate of polyurethanes, respectively, as sole source of energy, carbon, and nitrogen.<br /><br /> Whole genome sequencing of the strain revealed the presence of numerus catabolic genes for aromatic compounds. Growth on potential intermediates of 2,4-diaminotoluene degradation, other aromatic growth substrates and a comparison with a protein data base of oxygenases present in the genome, led to the proposal of a degradation pathway.Atanasoff-Kardjalieff, Kappelmeyer, Tischler, Pieper, Heipieper and Eberlein.Theoretical prediction of the S1-S0 internal conversion of 6-cyanoazulene.Ab initio complete active-space self-consistent field (CASSCF) and second-order Multireference Möller-Plesset perturbation (MRMP2) calculations were performed to examine the S1-S0 internal conversion of 6-cyanoazulene (6CNAZ). The azulene skeletons of 6CNAZ in S0 and S1 have features that resemble those of azulene. The stable geometry in S0 is characterized by (i) a C2v structure, (ii) an aromatic bond-equalized structure in which all the peripheral skeletal bond distances resemble an aromatic CC bond distance, and (iii) a single bond character of the transannular bond.<br /><br /> The stable geometry in S1 is characterized by a nonaromatic C2v structure. Contrary to similarities of the stable geometries in S0 and S1 between 6CNAZ and azulene, the conical intersection (S1/S0-CIX) of 6CNAZ is different from that of azulene. The S1/S0-CIX of 6CNAZ takes a planar structure, whereas that of azulene takes a nonplanar structure in the seven-membered ring (Amatatsu, Y.; Komura, K. J. Chem. Phys.<br /><br /> 2006, 125, 174311/1-8).