Volume Change during Thermal [4 + 4] Cycloaddition of [2.2] (9,10)Anthracenophane

Abstract

We show that the reaction path connecting the tethered bi(anthracene-9,10-dimethylene) and its photodimer proceeds stepwise via a diradicaloid transition state where one σ-bond is made before a second. The newly found transition state (TS) has a smaller molecular volume than either the reactant or the product giving an atomistic explanation to the recently found pressure catalyzed barrier lowering and rate enhancement. The density functional methods used include long-range contributions as required in a system where the dispersion interactions are significant. We discuss this transformation in the context of the diamond-to-graphite transition owing to the similarity of σ-bond breakage into a delocalized π-system. We also comment on the controversy surrounding the equilibrium geometries of photoisomerized cyclophanes, concluding that D2h symmetry in the photoisomer of the title molecule is a transition structure connecting a pair of degenerate ground state D2 geometries.

Gold(I)‐Catalyzed Conia‐ene Cyclization of Internal ϵ‐Acetylenic β‐Ketoesters under High Pressure.

“…Unfortunately, the accuracy of the volume calculation (inside a contour of 0.001 electrons Bohr −3 ) turned out to be insufficient, providing implausible values of molar volumes and, as a consequence, activation and reaction volumes. Such calculation of reaction volumes has been previously employed to support the mechanism involving pressure acceleration of the [4+4] cycloaddition of [2.2] (9,10)anthracenophane . A considerably better approximation was achieved employing the volume of the cavity calculated using the Polarizable Continuum Model (PCM) of solvation.…”

Mesoscale simulations of shockwave energy dissipation via chemical reactions

“…The parameterization of a ChemDID model involves determining inter-molecular and intra-molecular potentials, the molecular mass and the inertial parameter for the dynamics of the molecule radii and as well as the coupling constants, ν meso and ν rad , that describe the coupling between the internal DoFs and the molecular centers of mass and radii. In this paper we parameterized a model reactive material with thermo-mechanical properties similar to anthracene, a molecular material believed to be capable of endothermic, volume reducing chemistry; DFT calculations by Slepetz et al [22] show that the low-volume endothermic state of anthracene has an energy between 10-20 kcal/mol over the high-volume ground state.…”

Coarse grain model for coupled thermo-mechano-chemical processes and its application to pressure-induced endothermic chemical reactions

“…Such endothermic chemistry with volume reduction could provide the desired capability of shockwave energy dissipation. One possible system with such characteristics is the anthracene molecule; Jezowski et al [21] have found that the application of mechanical force reduces the rection rate involved in chemical bond formation, while Slepetz et al [22] have calculated a possible intermediate pathway occurring between reactants and products, which involves molecular volume reduction. With the potential energy fully determined in terms of the system variables, we can write the system Hamiltonian from which we will derive equations of motion:…”