In order to rationalize the observations seen in Fig. and Fig. , we extend the work of Ref. 4 to include a chemical rationale for the cavityinduced changes to the ground state reaction barrier. Fig. shows the density difference isosurfaces for the TS geometries for the endo (top) and exo (bottom) isomers for all three principle cavity polariation directions: x (left), Y (middle), and Z (right). The difference density function is defined as ∆ρ 00 (r) = ρ M 00 (r)ξ 00 (r), where ρ M 00 = Tr ph [ρ 00 ] = Tr ph [|Φ 0 ⟩⟨Φ 0 |] is the total ground state polaritonic density with the photon DOFs traced out. ξ 00 (r) = ψ * 0 (r)ψ 0 (r) is the bare electronic ground state density. The difference of these two densities portrays the effects of cavity-induced electronic redistribution around the molecule. The regions in which ∆ρ 00 (r) > 0 (red colored) indicates that a gain of electron density has occured, and depletion when ∆ρ 00 (r) < 0 (blue colored). Additional visualization angles are shown in Fig. in the Supporting Information. This effect can be rationalized chemically by considering that the cavity can induce redistribution (exchange of character) between bare occupied and unoccupied single-particle orbitals (e.g., HOMO ↔ LUMO), which allows for changes to the standard molecular orbital theory inside the cavity. The X-polarization direction showcased a simultaneous increase in TS barrier energy for the endo and exo isomers (see Fig. ), thus we expect that the potential chemical bond between the two reactant molecules is weakened by the presence of the cavity for both isomer configurations. Fig. show the ground state difference density isosurface for the (Fig. ) endo and (Fig. ) exo isomers with the cavity polarized along the X-direction of the molecule (see cartesian axes above Fig. ). The region between the reactant molecules is blue, which indicates that this region has been depleted of electron density. This region is also responsible for the formation of the intermolecular bond during the reaction. Since this region has lost these intermolecular bonding electrons, the TS geometry has been destabilized compared to outside the cavity. Contrary to this result, the Y-polarization of the cavity induced a stabilization of the TS barrier energy (Fig. ). Fig. show the difference density in this case, and, opposite to Fig. , we find an increase in electron density in the region between the reactant species, this strengthening the intermolecular bond at the TS geometry and reducing the TS barrier energy.