Mechanical energy alters chemical reactions. Although the mechanisms of mechanochemical reactions are not understood well, they have been utilized for alloying, polishing, lubrication and so on. On the other hand, tribochemical reactions which involve the interactions between frictional materials and the environment accelerate the decomposition of solid and surrounding molecules. It results in the emission of small particles and gases, bringing problems to environment and health. Mechanochemical and tribochemical reactions are often studied in different fields and in different societies. Even if similar reactions from each field are named differently, the same physics and chemistry operate in both reactions. Therefore, this study aimed at better understanding of some tribochemical reactions from the mechanochemical point of view. The main mechanism is proposed to be the emission of electrons, which is enhanced by the energy input onto the surface and surrounding molecules due to the breakage of chemical bonds and chemisorption of environmental molecules.