Via rate-limiting proton transfer to give the phenolate

2 Via rate-limiting proton transfer to give the phenolate 

If k2[Y [HS1 ], i.e. the proton transfer within the hydrogen-bonded complex 

In this case, the predicted rate law includes two reaction channels - both first order in phenol, with one first order in radical concentration and the other zero order. This behaviour has been found, for example, in the reaction between 2,2 -methylene-bis(4-methyl-6-terf-butylphenol) (ArOH) and 2,2-diphenyl-1-picrylhydrazyl (Y ) in Fig. 4.7 when acetonitrile, benzonitrile, acetone, cyclohexanone or DMSO are the solvents [19]. 

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