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1

Theoretical Inversion of Amino Acids (Alanine and Aspartic Acid) by Semi-empirical Methods

Mohamed M. E.

International Letters of Chemistry, Physics and Astronomy

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2013

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Vol. 7, iss. 1

37--44

EN

The inversion reaction coordinate of free amino acids (alanine, aspartic acid) have been computationally calculated by semi-empirical methods AM1. A transition state for free alanine and aspartic acid were obtained as a three membered ring in which the α-C-H and α-C-CH3 are slightly elongated, 1.2 and 2.17 Å respectively in the alanine transition state. The activation energy of alanine is 77.52 kcal/mol in the gas phase and 76.66 kcal/mol in aqueous phase, and for aspartic acid is 54.87 kcal/mol in the gas phase and 50.86 kcal/mol in aqueous phase.

2

Change of Prototropic Equilibria for Uracil when Going from Neutral Molecule to Charged Radicals. Quantum-Chemical Studies in the Gas Phase

Raczyńska E. D., Zientara K., Kolczyńska K., Stępniewski T. M.

Polish Journal of Chemistry

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2009

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Vol. 83, nr 5

821-834

EN

To understand various substitution, oxidation or degradation reactions for uracil, quantum-chem i calcalculations were performed for two classes of charged radicals (cations and anions) of uracil (U+ź and U-ź) and model compounds: phenol (P+ź and P-ź) and hydroxyazines (HP1-4+ź and HP1+-4-ź). In calculations, all possible eighteen prototropic tautomers-rotamers of U and all possible five prototropic tautomers-rotamers of P and HP1-4 were considered. Stabilities, internal effects and aromatic character, estimated for charged radicals, were compared with those observed previously for neutral molecules. The great est changes of the tautomeric preferences take place for radical anions. One-electron reduction stabilizes the keto and amide functions in studied compounds, whereas one-electron oxidation favors the enol function for ph nol and the amide function for uracil and hydroxyazines.

3

Termodynamika cykloprzyłączenia nitroetylenu do Z-C-fenylo-N-arylonitronów w świetle obliczeń AM1 i AM1/COSMO

Jasiński R., Mikulska M., Celej K., Barański A.

Czasopismo Techniczne. Chemia

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2007

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R. 104, z. 1-Ch

33-36

PL

Zbadano termodynamikę cykloaddycji nitroetylenu do Z-C-fenylo-N-arylonitronów. Ustalono, że czynniki termodynamiczne sprzyjają powstawaniu [2+3] cykloadduktów w niskich temperaturach i mało polarnym środowisku.

EN

The thermodynamics of nitroethene cycloaddition to Z-C-phenyl-N-arylnitrones have been studied. It has been found, that the thermodynamics parameters preffere the formation of [2+3] cycloadducts at low temperature and low polar solvents.

4

Widma UV 1,1-dinitroetylenu i 1-karbometoksy-1-nitroetylenu w świetle obliczeń ZINDO

Mikulska M., Jasiński R.

Czasopismo Techniczne. Chemia

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2005

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R. 102, z. 7-Ch

93--98

PL

Stosując algorytmy kwantowochemiczne, zbadano przejścia elektronowe dla 1,1-dinitroetylenu i 1-karbometoksy-1-nitroetylenu w zakresie podstawowego UV. Optymalizację geometrii przeprowadzono za pomocą hamiltonianu AM1, zaś obliczenia przejść elektronowych za pomocą metody ZINDO.

EN

Using quantumchemical algorithms the electron transition for 1,1-dinitroethene and 1-carbome-thoxy-1-nitroethene in the UV range were studied. AM1 Hamiltonian was used to the geometry optimization, while the electron transitions were calculated by means of ZINDO method.