Direct Experimental Evidence for Alkoxyl Radicals Reacting as Hydrogen Atom Donors toward Pyridines

Abstract

Nanosecond transient absorption spectroscopy was used to generate ethoxyl radicals and demonstrate that they react with 2,6-lutidine and 4-phenylpyridine to give the corresponding N-hydropyridinyl radicalsproducts of a novel hydrogen atom transfer from the alkoxyl radical to the nitrogen atom of the substituted pyridines. Nanosecond kinetics show that both reactions are rapid (k ∼ 107 M–1 s–1) in acetonitrile at room temperature. Rate constants measured for reaction of the ethoxyl vs. d 5-ethoxyl radical with 2,6-lutidine and 4-phenylpyridine show that both reactions exhibit primary H/D kinetic isotope effects for the hydrogen (deuterium) atom transfer reactions.