The reliability of three popular semiempirical quantum chemical methods (AMI, PM3, MNDO) for the treatment of tautomeric equilibria is tested in a series of five-membered nitrogen heterocycles. The known flaw of M N D O to overestimate the stability of compounds with two or more adjacent pyridine-like lone pairs is also present in AMI and to a somewhat lesser extent in PM3. Tautomeric species d...

In the present research, synthesis of new 2-(3-chlorobenzyl)-1H-benzimidazole derivatives bearing Nbenzylidene, 1,2,4-triazole and N-acylhydrazone moiety is investigated. These novel compounds have been tested for their antimicrobial effects against two of Gram-positive bacterial strains, namely Bacillus subtilis and Staphylococcus epidermidis, and four Gram-negative bacterial strains which wer...

Mixed aggregation of lithium dialkylamides with various LiX salts is studied by semiempirical (MNDO) computational methods. The relative stabilities of mixed aggregates of lithium diisopropylamide and lithium 2,2,6,6tetramethylpiperidide with LiCl as well as theenolates derived from acetone, cyclohexanone, and 2,4-dimethylpentanone are described. The unsolvated forms are compared with the analo...

the thermodynamic functions such as enthalpy (h), gibbs free energy (g) and entropy (s) ofpyrazole was theoretically studied at 5 different temperatures 25, 30, 35, 40 and 45°c by usinggussian o3, software. first, the structural optimization of isolated pyrazole was done in the gas phaseby appling the density functional theory (b3lyp) level with 3-21g, 6-31g and 6-31+g(d) basissets. moreover, v...

gamma and (b) alpha cage in zeolite ZK5. 2. Methodology The structure model of the zeolite H-ZK5 was obtained by an optimization using the semi-empirical method MNDO, since no experimental structure data were available. Moreover, the influence of the electric field of the proton has been examined. Two clusters were selected from the optimized zeolite structure, the neutral (Si2O7H6) and the aci...