Thermochemistry of the Smallest Hyperbolic Paraboloid Hydrocarbon: A High-Level Quantum Chemical Perspective

[5.5.5.5]hexaene is a [12]annulene ring with symmetrically bound carbon atom in its center. This the smallest hydrocarbon hyperbolic paraboloid shape. and related hydrocarbons are important building blocks organic materials chemistry. For example, penta-graphene—a puckered 2D allotrope of carbon—is comprised similar repeating subunits. Here, we investigate thermochemical kinetic properties at CCSD(T) level by means G4 protocol. We find that this system energetically stable relative to isomeric forms. isomers containing phenyl one or more acetylenic side chains higher energy ∆H298 = 17.5–51.4 kJ mol−1. can undergo skeletal inversion via completely planar transition structure; however, activation for process ∆H‡298 249.2 mol−1 level. demonstrates high configurational stability towards inversion. also π-bond shift reaction which proceeds relatively low-lying structure an 67.6 Therefore, expected proceed rapidly room temperature.