title: Nucleophilic substitution by a hydroxide ion at a vinylic carbon: ab initio and density functional theory studies on methoxyethene, 3-methoxypropenal, 2,3-dihydro-4H-pyran-4-one, and 4H-pyran-4-one.
abstract: Nucleophilic substitutions by a hydroxide ion at vinylic carbons of methoxyethene (system A), 3-methoxypropenal (system B), 2,3-dihydro-4H-pyran-4-one (system C), and 4H-pyran-4-one (system D) were calculated by Becke's three-parameter hybrid density functional-HF method with the Lee-Yang-Parr correlation functional (B3LYP//B3LYP) and the second-order Møller-Plesset theory (MP2//B3LYP) using the 6-31+G(d) and AUG-cc-pVTZ basis sets. In addition, bulk solvent effects (aqueous solution) were estimated by the polarized continuum (overlapping spheres) model (PCM-B3LYP//B3LYP) and the polarizable conductor PCM model (CosmoPCM-B3LYP//B3LYP). The mechanisms as well as the influence of resonance, cyclic strain, aromatic, and polar effects on the reactivity of the calculated systems were determined. In the gas phase the rate-determining step of nucleophilic vinylic substitutions by a hydroxide ion may be either addition of hydroxide ion at the vinylic carbon (systems A and B) or elimination of the leaving group (systems C and D). In aqueous solution, for all four systems investigated, addition of hydroxide ion at the vinylic carbon is rate determining.
authors.affiliation: Institut für Chemie, Karl-Franzens Universität Graz, Heinrichstr. 28, A-8010 Graz, Austria.
authors.forename: J
authors.initials: J
authors.lastname: Kóna
authors.forename: P
authors.initials: P
authors.lastname: Zahradník
authors.forename: W M
authors.initials: WM
authors.lastname: Fabian
mesh_terms: D000475:Alkenes / Q000737:chemistry*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D005030:Ethylenes / Q000737:chemistry*; D007202:Indicators and Reagents; D008958:Models, Molecular; D010944:Plants / Q000737:chemistry; D011522:Protons; D011753:Pyrones / Q000737:chemistry*; D014753:Vinyl Compounds / Q000737:chemistry*
chemical_list: D000475:Alkenes; D005030:Ethylenes; D007202:Indicators and Reagents; D011522:Protons; D011753:Pyrones; D014753:Vinyl Compounds