A THEORETICAL-STUDY OF SPIN-TRAPPING BY NITRONE - TRAPPING OF HYDROGEN, METHYL, HYDROXYL, AND PEROXYL RADICALS

The geometries and energetics of the spin trapping reaction of the nitrone function have been determined using ab initio methods at the Hartree-Fock and second-order Moller-Plesset levels with the 6-31G(d) and 6-31G(d,p) basis sets. Radicals (H-., (CH3)-C-., (OH)-O-., and (OOH)-O-.), the prototype nitrone spin trap (H2C=NHO), and the resultant spin adducts were examined to ascertain the most probable site of radical addition, the minimum-energy geometries of the adducts, and the energy changes involved in the addition reaction. The calculations show that addition clearly favors the C-site of the nitrone, with the O-site being the second location when double spin adducts form; this supports experimental observations. Double spin adducts an energetically preferred over monoadducts. Addition at the C-site is highly exothermic, with no activation energy barrier for any of the radicals studied.