Zeldovich mechanism is a chemical mechanism that describes the oxidation of nitrogen and NO formation, first proposed by the Russian physicist Yakov Borisovich Zeldovich in 1946. The reaction mechanisms read as
where  and  are the reaction rate constants in Arrhenius law. The overall global reaction is given by
The overall reaction rate is mostly governed by the first reaction (i.e., rate-determining reaction), since the second reaction is much faster than the first reaction and occurs immediately following the first reaction. At fuel-rich conditions, due to lack of oxygen, reaction 2 becomes weak, hence, a third reaction is included in the mechanism, also known as extended Zel'dovich mechanism (with all three reactions),
Assuming the initial concentration of NO is low and the reverse reactions can therefore be ignored, the forward rate constants of the reactions are given by 
where the pre-exponential factor is measured in units of cm, mol, s and K (these units are incorrect), temperature in kelvins, and the activation energy in cal/mol; R is the universal gas constant.