Browsing by Subject "Aromatic compounds"

Now showing 1 - 3 of 3
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    Accurate ring strain energies of unsaturated three-membered heterocycles with one group 13–16 element
    (American Chemical Society, 2022-05-02) Rey Planells, Alicia; Espinosa Ferao, Arturo; Química Orgánica
    High-quality ring strain energy (RSE) data for 1H-unsaturated (CH)2X parent rings, where X is a group 13–16 element, are reported in addition to the 2H-isomers of the pnictogenirene rings. RSE data are obtained from appropriate homosdesmotic reactions and calculated at the DLPNO-CCSD(T)/def2-TZVPP//B3LYP-D3/def2-TZVP(ecp) level. 1H-Tallirene and 1H-plumbirene have unique donor–acceptor structures between an acetylene π(CC) orbital and an empty p orbital of a metallylene subunit (a Dewar–Chatt–Duncanson description) and therefore cannot be described as proper rings but as pseudocyclic structures. Also, 1H-indirene and 1H-oxirene lack ring critical points and constitute borderline cases of pseudorings. 1H-Unsaturated rings exhibit enhanced RSE compared to their saturated homologues. The mechanism of ring strain relaxation by increasing the s character in the lone pair (LP) of group 15–16 elements is remarkable and increases on descending the groups. Furthermore, RSE is affected by the aromatic character of group 13 rings and certain aromatic or antiaromatic character in group 14 or 15–16 rings, respectively, which tend to vanish on descending the group as shown by NICS(1) values. 2H-Unsaturated rings were found only for group 15 elements (although only 2H-azirine shows a proper cyclic structure) and displayed lower RSE (higher stability) than the corresponding 1H-isomers.
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    An Approach for the Evaluation of Exposure Patterns of Urban Populations to Air Pollution
    (Elsevier, ) Pérez Ballesta, Pascual; Baeza Caracena, Antonia; Field, Robert A.; Fernández Patier, Rosalía; Galán Madruga, David; Connolly, Richard; De Saeger, Emile; Ingeniería Química; Centro Común de Investigación de la Unión Europea. Instituto de Medioambiente
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    Pd-catalyzed C(sp(3))-H functionalization/carbenoid insertion: all-carbon quaternary centers via multiple C-C bond formation
    (American Chemical Society, 2016-05-04) Gutierrez Bonet, Alvaro; Juliá Hernández, Francisco; Luis, Beatriz de; Martin, Ruben; Química Inorgánica
    A Pd-catalyzed C(sp3)-H functionalization/carbenoid insertion is described. The method allows for the rapid synthesis of bicyclic frameworks, generating all-carbon quaternary centers via multiple C–C bond-formations in a straightforward manner.