Embedding of the saddle point of index two on the PES of the ring opening of cyclobutene. Issue 23 (27th August 2015)

• Record Type: Journal Article
• Authors: Quapp, Wolfgang; Maria Bofill, Josep
• Is Part Of: International journal of quantum chemistry. Volume 115:Issue 23(2015:Dec. 05)
• Page Start: 1635
• Page End: 1649
• Publication Date: 2015-08-27
• Subjects: Quantum chemistry -- Periodicals; 541.28
• DOI: 10.1002/qua.24996
• Languages: English
• ISSNs: 0020-7608

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <p>The ring opening of cyclobutene is characterized by a competition of the two different pathways: a usual pathway over a saddle of index one (SP<sub>1</sub>) along the conrotatory behavior of the end groups, as well as a "forbidden" pathway over a saddle point of index two (SP<sub>2</sub>) along the disrotatory behavior of the end CH<sub>2</sub> groups. We use the system of ordinary differential equations for the method of the gentlest ascent dynamics (GAD) to determine saddle points of the potential energy surface (PES) of the ring opening of cyclobutene to <italic>cis</italic>‐butadiene. We apply generalized GAD formulas for the search of a saddle point of index two. To understand the relation of the different regions of the PES (around minimums, around SPs of index one or two) we also calculate valley‐ridge inflection (VRI) points on the PES using Newton trajectories (NT). VRIs and the corresponding singular NTs subdivide the regions of "attraction" of the different SPs. We calculate the connections of the SP<sub>2</sub> (in its different symmetry versions) with different SPs of index one of the PES by different "reaction pathways." We compare the possibilities of the tool of the GAD curves for the exploration of PESs with these of NT. The barrier of the disrotatory SP<sub>2</sub> is somewhat higher than the barrier of the conrotatory SP<sub>1</sub>, however, pathways across the slope to the SP<sub>2</sub> open additional reaction valleys. © 2015 Wiley Periodicals, Inc.</p> </abstract>