This article discusses the mechanisms of a photolytic reaction, the formation of formaldehyde in the earth＇s prebiotic atmosphere, and the synthesis of methanol by processing the stoichiometric matrices of their sets of elementary mechanistic steps by a computer program. For methanol synthesis, we will distinguish between unidirectional and reversible elementary mechanistic steps. These problems will be discussed in conjunction with a description of the structure of a program, CatKin, written in FORTRAN, that we have developed to compute reaction mechanisms and King-Altman-Hill＇s steady-state fluxes of reaction paths.