Redox reactions of transient species formed during pulse radiolysis of 2-pyridine carboxaldehyde and 2-pyridine methanol in aqueous solutions

Abstract

Rate constants for the reactions of e aq − , H and OH radicals with 2-pyridine carboxaldehyde and 2-pyridine methanol have been determined by pulse radiolysis technique. Reactions of reducing radicals such as acetone ketyl radicals and CO2 − with these compounds were also evaluated at various pHs. The species produced by the reaction of reducing radicals with these solutes was a strong reductant itself. While pyridinyl were produced in the case of 2-pyridine methanol, one-electron reduction of 2-pyridine carboxaldehyde led to the formation of PyCHOH radical. The one-electron reduction potential of PyCHOH radicals was estimated by establishing an equilibrium with MV+ radical cations to be −0.6V vs NHE. OH radical reaction with 2-pyridine carboxaldehyde gave an OH adduct, while in the case of 2-pyridine methanol, OH radicals reacted partly by H-abstraction from the −CH2OH group. SO4 − radical reaction with 2-pyridine carboxaldehyde produced a species which was reducing in nature. The rate constants for the reaction of e aq − and OH radicals are compared with similar values obtained in the case of other 2-pyridine derivatives to see if there is any electron-inductive effect.