C6h4–c6h10

Gajewski, Joseph J.

doi:10.1016/b978-012273351-2/50008-7

Cited by 1 publication

(8 citation statements)

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“…Niwayama et al calculated the activation energy for the rearrangement of 3-vinylcyclobutene to cis - and trans -hexatriene as 45.3 and 40.4 kcal mol –1 , respectively, at the RHF/6-31G*//3-21G level. Their result of 40.4 kcal mol –1 is too high relative to the experimental value of 26.8 kcal mol –1 . However, it is not surprising to observe such failures of the RHF method.…”

Section: Introductionmentioning

confidence: 65%

“…The molecule 1 rearranges to the biradical intermediate 2 by a well-known vinylcyclopropane rearrangement . Both radical centers in the intermediate 2 are allylic radicals; hence the intermediate 2 is stabilized by resonance effects.…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…3-Vinylcyclobutene rearranges to trans -hexatriene (Scheme ) with an activation energy of 26.8 kcal mol –1 . The formation of cis -hexatriene is slow and requires significantly higher temperatures . In 1996, Niwayama et al investigated substituent effects on rates and stereoselectivities of conrotatory electrocyclic reactions of cyclobutenes using the restricted Hartree–Fock (RHF) method with the 3-21G basis set.…”

Section: Introductionmentioning

confidence: 99%

“…Although thermal rearrangement of 2-vinylmethylenecyclopropane to 3-methylenecyclopentene was carried out experimentally ,,, and studied theoretically, its thermal rearrangement to benzene has not been explored experimentally yet. Similarly, although thermal rearrangement of 3-methylenecyclopentene to hexatriene is known, ,, the aromatization of 3-vinylcyclobutene has not been experimentally investigated yet. Hence, in this research, we will theoretically demonstrate that 2-vinylmethylenecyclopropane and 3-vinylcyclobutene may rearrange to benzene under suitable experimental conditions.…”

Section: Introductionmentioning

confidence: 99%

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Thermal Aromatizations of 2-Vinylmethylenecyclopropane and 3-Vinylcyclobutene

Bozkaya

Özkan

2012

J. Org. Chem.

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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.

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Section: Introductionmentioning

confidence: 65%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%