N-Hydroxypyridine-2-thione Esters as Radical Precusors in Kinetic Studies. Measurements of Rate Constants for Hydrogen Atom Abstraction Reactions

Article abstract of DOI:10.1021/ja00274a046

N-hydroxypyridine-2-thione esters were employed as radical precursors in kinetic studies.Radical chain reactions of the precursor esters gave 2,2-dimethyl-3-butenyl and 5-hexenyl.These radicals either were trapped by H-atom donors or rearranged, and the rate constants for trapping were determined from the known rate constants for rearrangement and measured product yields.For hydrogen atom donors that reacted too slowly to trap radicals before rearrangement, an estimate of the rate constants for hydrogen atom transfer was made from the yields of rearranged hydrocarbon and alkyl pyridyl sulfide (formed by scavenging of the alkyl radical by the precursor ester).The methods work for a variety of H-atom donors, including thiols, stannanes, phosphines, silanes, and reactive hydrocarbons.The rate constants determined for reduction of alkyl radicals by dicyclohexylphosphine, 1,4-cyclohexadiene, and THF are important for mechanistic studies of potential electron-transfer processes in ractions of nukleophiles with alkyl halides.