Browsing by Subject "computational chemistry"

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    Investigating the cyclization of enediyne analogs using density functional theory
    (2012) Estep, Dylan; Kerwin, Sean
    Enediynes are organic molecules that readily undergo a thermal rearrangement, now commonly known as the Bergman cyclization, to a cyclic para diradical form. Interest in this rearrangement was renewed when it was found to be crucial to the mechanism of cytotoxicity in a variety of natural products containing the enediyne structural moiety. Cyclization of these molecules leads to DNA strand scission and ultimately cell death. Recent efforts by medicinal chemists to discover therapeutically relevant enediyne derivatives have been complemented by computational approaches, which seek to compute energies and energetic barriers to cyclization that can accurately predict the behavior of these molecules in vivo. Here we demonstrate this approach for cis-hex-3-ene-1,5-diyne and two of its analogs using density functional theory, discuss the validity of its predictions, and investigate the effect of basis set on the description of these molecules’ reactivity.
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    The structure and vibrational modes of propargylene (HCCCH)
    (2012) Lewis, Cannada Andrew; Stanton, John F.
    The vibrational modes of propargylene were modeled at multiple levels of theory using the CFOUR quantum chemistry package. Then a potential energy plot was produced for two of the unsymmetric modes at both the UHF/CCSD, which allows the α electron orbitals and the β electron orbitals to be different, and ROHF/CCSD, which requires them to be the same except for any electrons which do not form a pair, levels of theory. The theoretical structure and vibrational modes were used to compare the more accurate representation of propargylene to the classic lewis structure version of the molecule and to discuss how resonance is used to show molecules that can not be accurately depicted using a single lewis structure. These calculations were also used to gain insight into the nature of the different energy levels of propargylene and as a starting point for more refined quantum mechanical calculations, which have not yet been carried out.