title: Formation of C4H4(•+) from the pyridine radical cation: a theoretical mechanistic and kinetic study.
abstract: The potential energy surface (PES) for the formation of C(4)H(4)(•+) from the pyridine radical cation by loss of HCN was determined from quantum chemical calculations using the G3//B3LYP method. The complete reaction pathways for the formation of the low-energy C(4)H(4)(•+) isomers, radical cations of methylenecyclopropene (MCP(•+)), vinylacteylene (VA(•+)), cyclobutadiene, and butatriene were obtained. Based on the PESs, a Rice-Ramsperger-Kassel-Marcus model calculation was performed to investigate the dissociation kinetics. The calculated dissociation rate constants agreed with the previous experimental data. It was predicted that a mixture of MCP(•+) and VA(•+) was formed by loss of HCN. The formation of MCP(•+) was more favored near the dissociation threshold and at high energies, whereas the formation of VA(•+) was more favored at the low energies corresponding to the ion lifetime of microseconds.
authors.affiliation: Department of Chemistry, Dongguk University-Seoul, Seoul 100-715, Korea.
authors.forename: Min Kyoung
authors.initials: MK
authors.lastname: Yim
authors.forename: Joong Chul
authors.initials: JC
authors.lastname: Choe
mesh_terms: D002412:Cations / Q000737:chemistry; D005609:Free Radicals / Q000138:chemical synthesis / Q000737:chemistry; D006856:Hydrogen Cyanide / Q000138:chemical synthesis / Q000737:chemistry; D007700:Kinetics; D011725:Pyridines / Q000737:chemistry*; D011789:Quantum Theory; D013816:Thermodynamics
chemical_list: D002412:Cations; D005609:Free Radicals; D011725:Pyridines; D006856:Hydrogen Cyanide; C023666:pyridine