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Molecular Orbital Energy (molecular + orbital_energy)

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Chemistry100%

Terms modified by Molecular Orbital Energy

  • molecular orbital energy level
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    Selected Abstracts

    Theoretical studies of some sulphonamides as corrosion inhibitors for mild steel in acidic medium

    INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 14 2010
    Eno E. Ebenso
    Abstract Density functional theory (DFT) at the B3LYP/6-31G (d,p) and BP86/CEP-31G* basis set levels and ab initio calculations using the RHF/6-31G (d,p) methods were performed on four sulfonamides (namely sulfaacetamide (SAM), sulfapyridine (SPY), sulfamerazine (SMR), and sulfathiazole (STI)) used as corrosion inhibitors for mild steel in acidic medium to determine the relationship between molecular structure and their inhibition efficiencies (%IE). The order of inhibition efficiency obtained was SMR > SPY > STI > SAM which corresponded with the order of most of the calculated quantum chemical parameters namely EHOMO (highest occupied molecular orbital energy), ELUMO (lowest unoccupied molecular orbital energy), the energy gap (,E), the Mulliken charges on the C, O, N, S atoms, hardness (,), softness (S), polarizability (,), dipole moment (,), total energy change (,ET), electrophilicity (,), electron affinity (A), ionization potential (I), the absolute electronegativity (,), and the fraction of electrons transferred (,N). Quantitative structure activity relationship (QSAR) approach has been used and a correlation of the composite index of some of the quantum chemical parameters was performed to characterize the inhibition performance of the sulfonamides studied. The results showed that the %IE of the sulfonamides was closely related to some of the quantum chemical parameters but with varying degrees/order. The calculated %IE of the sulfonamides studied was found to be close to their experimental corrosion inhibition efficiencies. The experimental data obtained fits the Langmuir adsorption isotherm. The negative sign of the EHOMO values and other thermodynamic parameters obtained indicates that the data obtained supports physical adsorption mechanism. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source]

    Nitrobenzene toxicity: QSAR correlations and mechanistic interpretations,

    JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 10 2003
    Alan R. Katritzky
    Abstract The overall five-parameter QSAR correlation [ in terms of log(IGC50,1)] based on CODESSA-PRO methodology for the aquatic toxicity of 97 substituted nitrobenzenes to the ciliate Tetrahymena pyriformis supports previous conclusions that hydrophobicity and electrophilic reactivity control nitrobenzene toxicity. Correcting for the ionization of acidic species (picric and nitrobenzoic acids) improves the results: . Consideration of the total set of 97 compounds suggests two mechanisms of toxic action. A subset containing 43 compounds favorably disposed to reversible reduction of nitro group with respect to the single occupied molecular orbital energy, ESOMO correlated well with just four theoretically derived descriptors: . Another set of 49 substances predisposed to aromatic nucleophilic substitution modeled well () with five descriptors. Copyright © 2003 John Wiley & Sons, Ltd. [source]

    Artemisinin Derivatives with Antimalarial Activity against Plasmodium falciparum Designed with the Aid of Quantum Chemical and Partial Least Squares Methods

    MOLECULAR INFORMATICS, Issue 8 2003

    Abstract Artemisinin derivatives with antimalarial activity against Plasmodium falciparum resistant to mefloquine are designed with the aid of Quantum Chemical and Partial Least Squares Methods. The PLS model with three principal components explaining 89.55% of total variance, Q2=0.83 and R2=0.92 was obtained for 14/5 molecules in the training/external validation set. The most important descriptors for the design of the model were one level above the lowest unoccupied molecular orbital energy (LUMO+1), atomic charges in atoms C9 and C11 (Q9) and (Q11) respectively, the maximum number of hydrogen atoms that might make contact with heme (NH) and RDF030,m (a radial distribution function centered at 3.0,Å interatomic distance and weighted by atomic masses). From a set of ten proposed artemisinin derivatives, a new compound (26), was predicted with antimalarial activity higher than the compounds reported in literature. Molecular graphics and modeling supported the PLS results and revealed heme-ligand and protein-ligand stereoelectronic relationships as important for antimalarial activity. The most active 26 and 29 in the prediction set possess substituents at C9 able to extend to hemoglobin exterior, what determines the high activity of these compounds. [source]