Chapter 13 – Methods for studying chain reactions

Methods for studying chain reactions appeared in parallel with their discovery and study. Experimental evidence for the chain mechanism of the process and participation in it of free atoms and radicals gained significance at the first stage of development of the kinetics of chain reactions (1920-1940). In this concern, this chapter considers the proofs that include high quantum yield, initiator of chain reaction, influence of wall, and inhibitors of chain reactions. Further, this chapter discusses methods of identification of radicals and intermediate products of chain reaction. The method of metallic mirrors was first to be used for the identification of radicals formed in the gas mixture. Later the toluene method appeared and participation of radicals was concluded from the formation of dibenzyl from toluene added to the reaction mixture. Then researchers began to use widely the ESR method for the identification of radicals and study of the kinetics of their transformation. However, one often meets the situation when the concentration of radicals is so low that the ESR method does not allow their detection. Then compounds, traps of free radicals, are used, such as (CH 3 ) 3 CN(O). The latter reacts with a free radical to give the stable nitroxyl radicals detected by the ESR method.