Method of Radical and Spin Traps

The aim of this section is to give a concise description of the nse of traps, note the most popnlar and newly recommended traps, as well as underline the possible artifacts connected with the trap applications to ion-radical reactions. There are traps for ion-radicals and neutral radicals resulting from ion-radical disintegration. 

4-dihydroxybenzoic acid is an effective trap for cation-radicals such as the cation-radical from 2,2 -azino-bis[3-ethylbenzothiazoline-6-snlfonic acid] (Lee et al. 2006). In this case, trapping leads to cation-radical decolorization measnred by a diminntion of optical absorption. 

The problem of radical trapping is also relevant becanse radicals are often the primary products of ion-radical transformations. The radicals are, as a rnle, not stable, and special traps—radical and spin—are used to reveal them. 

Radical traps belong to the class of stable free radicals, for example, of the nitroxyl or phenoxyl type. Interacting with radicals prodnced by a reaction, radical traps give diamagnetic compounds. One can follow the progress of the reaction by a decreasing intensity of the ESR spectrum of the radical trap. 

Nitroso compounds, nitrones, and other diamagnetic molecules are used as spin traps. Capturing radicals prodnced in the reaction, spin traps form the so-called spin adducts—stable nitroxyl radicals easily detectable by ESR spectroscopy. In other words, the progress of the reaction can easily be followed by an increasing intensity of the spin-adduct signal. By and large, the method of traps reveals radicals by the disappearance (or appearance) of the ESR signal. 

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