The transition state of the automerization reaction of cyclobutadiene: A theoretical approach using the Restricted Active Space Self Consistent Field method

[Display omitted] •The transition state geometry for the automerization of cyclobutadiene is an isosceles trapezium.•Enhanced π-π dynamic electron correlation is responsible.•The calculated energy barrier is 9.62 kcal/mol (0.417 eV). The application of the Restricted Active Space Self Consistent Fie...

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Bibliographic Details
Published in:Chemical physics letters 2018-11, Vol.711, p.166-172
Main Authors: Varras, Panayiotis C., Gritzapis, Panagiotis S.
Format: Article
Language:English
Subjects:
Cyclobutadiene automerization
Cyclobutadiene RASSCF
Cyclobutadiene transition state
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Summary:[Display omitted] •The transition state geometry for the automerization of cyclobutadiene is an isosceles trapezium.•Enhanced π-π dynamic electron correlation is responsible.•The calculated energy barrier is 9.62 kcal/mol (0.417 eV). The application of the Restricted Active Space Self Consistent Field (RASSCF) quantum chemical method using an extended active space and including σ-σ, π-σ and π-π dynamical electron correlation shows that the transition state structure for the automerization reaction of cyclobutadiene is an isosceles trapezium. This transition state is obtained without any symmetry constraints. The calculated energy barrier height involving the zero point vibrational energy corrections is 9.62 kcal∙mol−1 (0.417 eV), with the corresponding rate constant being equal to 0.18 × 109 s−1 (or 7.1 × 1010 s−1 in case of using the vibrational energy splitting tunneling method).
ISSN:0009-2614
1873-4448
DOI:10.1016/j.cplett.2018.09.028