We study the Chapman-Jouguet (CJ) model and the selfsimilar Zeldovich-von Neumann-Döring (SZND) model in chemically reacting gas flows. We discover some basic relationships among ignition temperature Ti, total chemical binding energy Q, and the adibatic exponent γ of polytropic gas. From these relations, we can determine when temperatures along the SZND burning solutions are higher than the ignition temperature Ti. We also study the all possible selfsimilar solutions for the SZND-model. From these results, we can determine when selfsimilar solutions for the CJ-model are the limits of selfsimilar solutions of the SZND model when the reaction rate tends to infinity.