CW AND FT TIME-RESOLVED EPR INVESTIGATION OF THE QUENCHING REACTION OF THE 2-HYDROXYPROPAN-2-YL RADICAL

The secondary quenching reactions of the 2-hydroxypropan-2-yl radical produced by photolysis of pyrazine, quinoxaline, and p-benzoquinone in 2-propanol were investigated with time-resolved EPR. The quenching ra te constants are 6.6 x 10(6), 1.2 x 10(8), and similar to 10(8) M(-1) s(-1) for pyrazine, quinoxaline, and p-benzoquinone, respectively. The time profiles of the transient EPR signals of pyrazinyl and 2-hydroxy propan-2-yl radicals were measured by FT-EPR and analyzed in detail in terms of a reaction scheme involving the primary hydrogen abstraction reaction and the subsequent quenching reaction. It is found that half of the signal intensity of the pyrazinyl radical arises from polariza tion transfer accompanying 2-hydroxypropan-2-yl quenching by pyrazine.