PROTON AFFINITY OF THE STABLE FREE-RADICAL 2,2,6,6-TETRAMETHYL-1-PIPERIDINYLOXY MEASURED BY THE KINETIC METHOD

Proton-bound dimers can be generated between the stable free radical, 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), and various reference co mpounds in a chemical ionization source. The individual mass-selected dimers dissociate upon collision to yield the protonated monomers as t he only product ions. From their relative abundances the kinetic metho d yields a value of 209.5 +/- 1.0 kcal mol(-1) for the proton affinity of the TEMPO radical. The proton affinity is compared to that of m-me thylphenoxyl and other oxy radicals.