We introduce and test a new computational approach to calculating the intrinsic reaction-path and, from there, kinetic and dynamic information for reactions involving the breaking-forming of covalent bonds in large molecules. It is an extension of the integrated molecular orbital method with harmonic cap to follow the intrinsic reaction-path. We have named the method RAte constant calculation with Integrated Levels (RAIL). We show that the new scheme reproduces the behavior of a benchmark calculation for some kinetic and dynamic properties, such as, the minimum energy path and ground-state vibrationally adiabatic curves, the localization of the bottleneck on the reaction path, and the non-Arrhenius behavior of the rate constants with tunneling effect over the temperature range 298-1500 K. Moreover, the new scheme shows little dependency on which "low-level" is used in the computation.