When oxidised by the Ti(III)–hydrogen peroxide system in particular ranges of acidity, phenol, quinol, m- and p-fluorophenol, p-chlorophenol, and fluorobenzene each form one or more radical adducts, by combination with the hydroxy-radical, which are observable by electron spin resonance spectroscopy. These adducts are susceptible to acid- and/or base-catalysed reactions to give other radicals whose spectra can be observed; e.g., in a strongly acid medium, those from both phenol and fluorobenzene give, by different mechanisms, the phenoxy-radical. The spectra of adducts of anisole and of acetanilide with the hydroxy-radical have not been detected spectroscopically, although other observations provide evidence for their formation; these species are apparently more rapidly destroyed than the parent member of the series (the hydroxycyclohexadienyl radical), and possible destruction processes, for both weakly and strongly acidic media, are discussed.