Thermal aromatizations of 2-vinylmethylenecyclopropane and 3-vinylcyclobutene.
A comprehensive theoretical investigation of thermal rearrangements of 2-vinylmethylenecyclopropane and 3-vinylcyclobutene is carried out employing density functional theory and high level ab initio methods, such as the complete active space self-consistent field, multi-reference second-order Møller-Plesset perturbation theory, and coupled-cluster singles and doubles with perturbative triples. In all computations, Pople's polarized triple-ζ split valence basis set, 6-311G(d,p), is utilized. The potential energy surface for the relevant system is explored to provide theoretical insights for the thermal aromatizations of 2-vinylmethylenecyclopropane and 3-vinylcyclobutene. The rate constant for each isomerization reaction is computed using the transition state theory. The simultaneous first-order ordinary-differential equations are solved numerically for the considered system to obtain time-dependent concentrations, hence the product distributions at a given temperature. Our results demonstrate that at high temperatures thermal aromatizations of 2-vinylmethylenecyclopropane (at 700 °C and higher) and 3-vinylcyclobutene (at 500 °C and higher) are feasible under appropriate experimental conditions. However, at low temperatures (at 500 °C and lower), 2-vinylmethylenecyclopropane yields 3-methylenecyclopentene as a unique product, kinetically, and the formation of benzene is not favorable. Similarly, at 300 °C and lower temperatures, 3-vinylcyclobutene can only yield trans-1,3,5-hexatriene (major) and cis-1,3,5-hexatriene (minor). At 300 < T < 500 °C, 3-vinylcyclobutene almost completely yields 1,3-cyclohexadiene. Hence, our computations provide a useful insight for the synthesis of substituted aromatic compounds. Further, calculated energy values (reaction energies and activation parameters) are in satisfactory agreement with the available experimental results.
Department of Chemistry, Atatürk University, Erzurum 25240, Turkey. ugur.bozkaya@atauni.edu.tr
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Bozkaya
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D003503:Cyclobutanes / Q000737:chemistry*; D003521:Cyclopropanes / Q000737:chemistry*; D006841:Hydrocarbons, Aromatic / Q000138:chemical synthesis / Q000737:chemistry; D007700:Kinetics; D015394:Molecular Structure; D011789:Quantum Theory; D013237:Stereoisomerism; D013696:Temperature; D014753:Vinyl Compounds / Q000737:chemistry*
C575958:2-vinylmethylenecyclopropane; C575959:3-vinylcyclobutene; D003503:Cyclobutanes; D003521:Cyclopropanes; D006841:Hydrocarbons, Aromatic; D014753:Vinyl Compounds