This paper presents a proof for the semiglobal asymptotic stabilization of stirred jacketed chemical reactors under PID control, which is based on results from nonlinear singularly perturbed systems. A novel PID control configuration is developed in terms of a parameter that is directly related to the size of the region of attraction and the closed-loop performance. The only prior information required is an upper bound of the heat transfer coefficient. It is shown that, in the high-gain limit, the proposed PID control approaches the performance of the inverse dynamics control law. Numerical simulations are provided to support our theoretical findings.