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  • 1970-1974  (1)
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    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Kurven potentieller Energie von Systemen mit H-Brücken wurden im Fall von H2O-, CH3OH- und HCOOH-Dimeren und für das Hydrogen-Maleatanion mittels eines modifizierten CNDO-Verfahrens berechnet, wo für Rumpf-σ- und -π-Elektronen jeweils verschiedene Resonanzintegrale und verschiedene Bindungsparameter für =O und -O- verwendet und wo die Rumpfpotential-Integrale für O-H, C=O und O...O semiempirisch bestimmt werden. Die Resultate sind 1) eine Potentialkurve mit einem einfachen Minimum für lineare Ketten von H2O und CH3OH, 2) eine symmetrische Potentialkurve mit zwei Minima für das cyclische Diniere von HCOOH und 3) eine Potentialkurve mit einem flachen Minimum für das Maleatanion. Konfigurationsanalyse ergab einen Beitrag von 39% für die ionischen Strukturen.
    Notes: Abstract The potential energy curves of hydrogen-bonded systems were calculated for the water, methanol, and formic acid dimers and for the hydrogen maleate ion by a modified CNDO/2 method, the core resonance integrals betweenσ-electrons being distinguished from those betweenπ-electrons, the different bonding parameters being used for -O- and =O, and the core potential integralsV AB c for O-H, C=O, and O...O being determined semi-empirically. Consequently, the following results were obtained: 1) a potential energy curve with a single minimum atr(O-H)=0.95 Å and with a concavity near 1.70 Å for the linear chain dimers of water and methanol; 2) a symmetrical potential energy curve with two minima atr(O-H)=0.95 and 1.78 Å for the cyclic dimer of formic acid; 3) a flat-bottomed symmetrical potential energy curve for the hydrogen maleate ion. The configuration analysis method was applied to the hydrogen-bonded systems; the contributions of the covalent ((O-H-O)−1) and ionic (O−H+O−) structures being 54% and 39%, respectively, for the symmetrical hydrogen bonding of the hydrogen maleate ion.
    Type of Medium: Electronic Resource
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