The desilylation of PTA (Supplementary Material, Figure ) was chosen as the model reaction for the present study. The VSC of the Si-C stretching vibrational mode (ν Si-C ; 860 cm -1 , blue curve in Figure ) of PTA has shown to retard the Si-C bond scission dynamics [3], prompting us to do a detailed thermodynamic study, varying the ħΩ R . Vibrational strong coupling of the ν Si-C of PTA is achieved using a Fabry-Pérot cavity assembled in a temperaturecontrollable and demountable IR cell (purchased from Specac) equipped with holes to inject the liquids. An airfilled Fabry-Pérot cavity (empty cavity) is built in the IR cell by placing a Mylar spacer (6 ± 1 µm thick with a hollow central region) on top of an Au-coated ZnSe window (bottom mirror), which is then covered by a top mirror of Au sputtered on a ZnSe substrate having an inlet and outlet hole for sample injection. To protect the Au from the reactants, a 200-nm-thick SiO 2 (glass) was deposited on top of the Au mirrors. The IR cell is then closed by tightening the screws on the top lid. Such an empty cavity has many equally spaced modes in the IR whose periodicity is determined by the path length of the cavity (Figure ). Using a screwdriver, the empty cavity path length is then fine-tuned by adjusting the screws on the cell such that The desilylation of PTA Figure ) was chosen as the m study. The VSC of the Si-C s (ν Si-C ; 860 cm -1 , blue curve in to retard the Si-C bond scissi us to do a detailed thermodyn Vibrational strong coupling o using a Fabry-Pérot cavity a controllable and demountab Specac) equipped with holes filled Fabry-Pérot cavity (em cell by placing a Mylar spacer central region) on top of a (bottom mirror), which is th of Au sputtered on a ZnSe su outlet hole for sample injectio reactants, a 200-nm-thick SiO top of the Au mirrors. The IR c ing the screws on the top lid many equally spaced modes is determined by the path len Using a screwdriver, the emp fine-tuned by adjusting the s stry under vibrational strong coupling of ∆(∆G ‡ ) with e higher energy C compared to activity up to a orted earlier [3]. ges in the thersplitting, their C induced ħΩ R .