Bond Orbital Analysis (bond + orbital_analysis)

Distribution by Scientific Domains
Chemistry100%

Kinds of Bond Orbital Analysis

  • natural bond orbital analysis
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    Selected Abstracts

    ChemInform Abstract: Electronic Structure of 3d [M(H2O)6]3+ Ions from ScIII to FeIII: A Quantum Mechanical Study Based on DFT Computations and Natural Bond Orbital Analyses.

    CHEMINFORM, Issue 35 2001
    Bernd Kallies
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

    NMR spectra, GIAO and charge density calculations of five-membered aromatic heterocycles

    MAGNETIC RESONANCE IN CHEMISTRY, Issue 7 2007
    Alan R. Katritzky
    Abstract The B3LYP/6-31 + G(d) molecular geometry optimized structures of 17 five-membered heterocycles were employed together with the gauge including atomic orbitals (GIAO) density functional theory (DFT) method at the B3LYP/6-31 + G(d,p), B3LYP/6-311 + + G(d,p) and B3LYP/6-311 + G(2d,p) levels of theory for the calculation of proton and carbon chemicals shifts and coupling constants. The method of geometry optimization for pyrrole (1), N -methylpyrrole (2) and thiophene (7) using the larger 6-311 + + G(d,p) basis sets at the B3LYP/6-31 + G(d,p), B3LYP/6-311 + + G(d,p), B3LYP/6-31 + G(2d,p) and B3LYP/cc-pVTZ levels of theory gave little difference between calculated and experimental values of coupling constants. In general, the 1H and 13C chemical shifts for all compounds are in good agreement with theoretical calculations using the smaller 6-31 basis set. The values of nJHH(n = 3, 4, 5) and rmnJCH(n = 1, 2, 3, 4) were predicted well using the larger 6-31 + G(d,p) and 6-311 + + G(d,p) basis sets and at the B3LYP/6-31 + G(d,p), B3LYP/6-311 + + G(d,p), B3LYP/6-31 + G(2d,2p) levels of theory. The computed atomic charges [Mülliken; Natural Bond Orbital Analysis (NBO); Merz-Kollman (MK); CHELP and CHELPG] for the B3LYP/6-311 + + G(d,p) geometry optimized structures of 1,17 were used to explore correlations with the experimental proton and carbon chemical shifts. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    A predicted new type of directional noncovalent interaction

    INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 12 2007
    Jane S. Murray
    Abstract The electrostatic potentials computed on the surfaces of a series of molecules R3X, where X is a Group V atom, show that some of these atoms have regions of positive potential on their outer surfaces, approximately on the extensions of the RX bonds. This suggests the likelihood of weak, directional noncovalent interactions between such atoms and nucleophiles, paralleling what has already been established for Groups VI and VII. The origins and relative strengths of the positive regions are explained in terms of the ,-hole concept, supported by natural bond orbital analyses. MP2/6-311++G(3df,2p) calculations confirm the formation of stable complexes between five such Group V molecules and the model nucleophile HCN. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source]

    2,3,4,5,6-Penta­nitro­aniline 1,2-dichloro­ethane disolvate: `push,pull' deformation of aromatic rings by intra­molecular charge transfer

    ACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2006
    Sergiy V. Rosokha
    The title compound, C6H2N6O10·2C2H4Cl2, forms layered stacks of penta­nitro­aniline mol­ecules, which possess twofold symmetry. The voids between these stacks are occupied by dichloro­ethane mol­ecules, which reside near a 2/m symmetry element and display pseudo-inversion symmetry. The C atoms in one of the two solvent mol­ecules are threefold disordered. In the penta­nitro­aniline mol­ecule, considerable distortion of the benzenoid ring, coupled with the short C,N(H2) bond and out-of-plane NO2 twistings, point to significant intra­molecular `push,pull' charge transfer at the amino- and nitro-substituted (ortho and para) positions, as theoretically quantified by natural bond orbital analysis of the ,-electron density. [source]

    Does Negative Hyperconjugation Assist Enzymatic Dehydrogenations?

    CHEMPHYSCHEM, Issue 9 2007
    Gloria Tabacchi Dr.
    Enzyme mechanisms: Using ab initio methods and natural bond orbital analysis, negative hyperconjugation is shown to govern L -lactate oxidation chemistry and may help to determine its enzymatic dehydrogenation mechanism. The picture shows the negative hyperconjugation interaction between the lone pair on the oxygen atom and the ,*(C,H,) orbital. [source]

    Homolysis of N -alkoxyamines: A Computational Study

    CHEMPHYSCHEM, Issue 2 2006
    Anouk Gaudel-Siri Dr.
    Abstract During nitroxide-mediated polymerization (NMP) in the presence of a nitroxide R2(R1)NO., the reversible formation of N -alkoxyamines [PON(R1)R2] reduces significantly the concentration of polymer radicals (P.) and their involvement in termination reactions. The control of the livingness and polydispersity of the resulting polymer depends strongly on the magnitude of the bond dissociation energy (BDE) of the CON(R1)R2bond. In this study, theoretical BDEs of a large series of model N -alkoxyamines are calculated with the PM3 method. In order to provide a predictive tool, correlations between the calculated BDEs and the cleavage temperature (Tc,), and the dissociation rate constant (kd,), of the N -alkoxyamines are established. The homolytic cleavage of the NOC bond is also investigated at the B3P86/6-311++G(d,p)//B3LYP/6-31G(d), level. Furthermore, a natural bond orbital analysis is carried out for some N -alkoxyamines with a OCON(R1)R2fragment, and the strengthening of their CON(R1)R2bond is interpreted in terms of stabilizing anomeric interactions. [source]

    Preparation, Crystal Structure and Theoretical Calculation of N -(Pyrimidin-2-yl)- N, -methoxycarbonyl-thiourea

    CHINESE JOURNAL OF CHEMISTRY, Issue 4 2007
    Ying-Hui Ren
    Abstract The compound, N -(pyrimidin-2-yl)- N, -methoxycarbonyl-thiourea, has been synthesized. The single crystal structure has been determined by an X-ray diffractometer. The crystal belongs to triclinic with space group P -1 and a=0.72152(4) nm, b=0.8056(4) nm, c=0.90772(5) nm, ,=105.141(4)°, ,=94.588(4)°, ,=115.415(4)°, F(000)=220, the unit cell volume V=0.45704(4) nm3, the molecule number in one unit cell Z=2, the absorption coefficient ,=0.333 mm,1, the calculated density Dc=1.542 g/cm3. The theoretical investigation of the title compound was carried out with B3LYP/6-311G, HF/6-311G and MP2/6-311G methods, and the atomic charges and natural bond orbital analysis were also discussed. [source]