Vibrational strong coupling (VSC) is currently emerging as a tool to control chemical dynamics. Here we study the impact of strong coupling strength, given by the Rabi splitting energy (ħΩR), on the thermodynamic parameters associated with the transition state of the desilylation reaction of the model molecule 1-phenyl-2-trimethylsilylacetylene. Under VSC, the enthalpy and entropy of activation determined from the temperature-dependent kinetic studies varied nonlinearly with the coupling strength. The thermodynamic parameters of the noncavity reaction did not show noticeable variation, ruling out concentration effects other than the enhanced ħΩR for the changes observed under VSC. The difference between the total free energy change under VSC and in noncavity was relatively smaller possibly because the enthalpy and entropy of activation compensate each other. This thermodynamic study gives more insight into the role of collective strong coupling on the transition state that leads to modified dynamics and branching ratios.