Search results for "COMPUTATION"
showing 10 items of 7362 documents
Toward an understanding of the selectivity in domino reactions. A DFT study of the reaction between acetylenedicarboxylic acid and 1, 3-Bis(2-furyl)p…
2000
The mechanism of the domino reaction between acetylenedicarboxylic acid and 1,3-bis(2-furyl)propane has been theoretically studied in the framework of density functional theory. This domino process comprises two consecutive cycloaddition reactions: the first one is initialized by the nucleophilic attack of the C5 position of the furan ring to a conjugate position of acetylenedicarboxylic acid to give a zwitterionic intermediate, which by a subsequent ring-closure process affords an oxanorbornadiene intermediate. The second reaction is an intramolecular concerted cycloaddition of this intermediate to give the final dioxapentacyclic adduct. For the second cycloaddition, which corresponds to t…
Synthesis of methyl derivatives of linear and angular thienocoumarins and thiopyranocoumarins
1998
New linear and angular thienocoumarins and thiopyranocoumarins were synthesized. The key intermediates were appropriate methyl derivatives of 7-mercaptocoumarin, which were condensed with chloro-ketones or propargyl chloride. Thioethers were cyclized under various conditions in order to determine which methods produced the best yields of the desired thienocoumarins 15, 16, 17, 18, 22, 23, 24, 27 and thiopyranocoumarins 28 and 29.
Discrete supramolecular donor-acceptor complexes
2009
The renewed interest in noncovalently associating electroactive molecules arises in part from the quest for new organic materials that convert solar energy into electrical/ chemical equivalents. In this context, the formation of charge-separated states is a key prerequisite. Charge-transfer events triggered by light have been studied in supramolecular donor–acceptor systems based on hydrogen bonds and coordinative metal bonds. Although many of the most widely utilized electroactive fragments feature large pconjugated surfaces, to date the use of p–p aromatic interactions has mainly been limited to the construction of semi-infinite ensembles of chromophores either to achieve charge transport…
Quantification of DNA and RNA: a Quantitative Visual Comparison
2002
The analytical procedure for the quantification of DNA and RNA described is the quantitative visual comparison of an unknown sample with known standards. This is quick and easy to do, suitable for amounts of sample as small as 10 ng. Keywords: DNA; RNA; rapid quantification
Ab Initio Study on the Mechanism of Tropospheric Reactions of the Nitrate Radical with Haloalkenes: Chloroethene
2000
Energy landscapes in diexo and exo/endo isomers derived from Li2B12H12
2010
Abstract In the pursuit of detecting the first endohedral polyhedral borane complex, we report a quantum-chemical computational study of energy landscapes for diexo isomers derived from Li 2 B 12 H 12 and the exo/endo isomer Li@{LiB 12 H 12 }. Geometries, electronic structure and energy barriers are computed for the interconversion between diexo isomers and the exo / endo isomer, the latter leading to a thermal injection / ejection mechanism of Li + from outside / inside the complex [LiB 12 H 12 ] − .
ChemInform Abstract: Synthesis of Methyl Derivatives of Linear and Angular Thienocoumarins and Thiopyranocoumarins.
2010
New linear and angular thienocoumarins and thiopyranocoumarins were synthesized. The key intermediates were appropriate methyl derivatives of 7-mercaptocoumarin, which were condensed with chloro-ketones or propargyl chloride. Thioethers were cyclized under various conditions in order to determine which methods produced the best yields of the desired thienocoumarins 15, 16, 17, 18, 22, 23, 24, 27 and thiopyranocoumarins 28 and 29.
Cover Feature: Molecular Basis of the Chemiluminescence Mechanism of Luminol (Chem. Eur. J. 20/2019)
2019
Self-assembly through non-coordinating intermolecular forces, part 2 [1]. Synthesis, crystal structure and packing of [Cu2(μ-phthalazine) 3(phthalazi…
2008
Abstract Treatment of the copper(I) trifluoromethanesulphonate toluene complex {[Cu(CF3SO3)]2 · C6H5Me} (1) with phthalazine (phtz, C8H6N2) in dichloromethane-acetonitrile solution yielded, via the bis(acetonitrile)tris(μ-phthalazine)dicopper(I) trifluoromethanesulphonate intermediate (2), the novel bis(phthalazine)tris(μ-phthalazine)dicopper(I) trifluoromethanesulphonate salt (3). Compound 3 was completely characterised and the molecular structure determined by single-crystal X-ray diffraction. Complex 3 crystallises in the monoclinic system, space group C2/c, with a = 26.9527(10), b = 10.9558(7), c = 19.2104(10) Å , β = 127.268(2)◦, V = 4514.3(4) Å3 and Z = 4. The copper(I) coordination g…
(1Z,3Z)-1,4-Di(pyridin-2-yl)buta-1,3-diene-2,3-diol: The Planar Highly Conjugated Symmetrical Enediol with Multiple Intramolecular Hydrogen Bonds
2002
1H, (13)C, and (15)N NMR spectral data show that in chloroform solution (1Z,3Z)-1,4-di(pyridin-2-yl)buta-1,3-diene-2,3-diol, OO, is in ca. 9:1 equilibrium with (3Z)-3-hydroxy-1,4-di(pyridin-2-yl)but-3-en-2-one, OK, while no 1,4-di(pyridin-2-yl)-2,3-butanedione, KK, was detected. The species present in the tautomeric mixture were identified by comparing their experimental chemical shifts with those known for similar compounds as well as with the theoretically calculated (GIAO-HF/DFT) values. Ab initio calculations show that OK and especially the highly conjugated OO forms are preferred in the tautomeric mixtures both in vacuo and in chloroform solution. Comparison of experimental (Arrhenius)…