Abstract <p>A universal method for constructing the canonical profile of an elementary chemical reaction by reducing it to the same form as that for a thermoneutral reaction is considered. It is based on information about three stationary points of the potential energy surface of the system (the initial, transition, and final states) and the vector of normal vibrations with an imaginary frequency. An additive approach to the determination of the activation energy of thermoneutral reactions is presented for the radical reactions of H atom abstraction. This approach makes it possible to determine the rate constants of asymmetric reactions through a smaller number of rate constants of symmetric reactions.</p>