Transient and Stable Products in the Pulse Radiolysis of Some Dihydropyrimidine Solutions

Summary

The radiation chemistry of three 5,6-dihydropyrimidines (DHU, 5-Me-DHU, 6-Me-DHU) has been investigated by pulse radiolysis. Some rate constants for the reaction of the primary water radicals, OH, H, and e_aq⁻, with these compounds are reported. Reaction with e_aq⁻ gives transient absorptions below 500 nm without a defined peak. Reaction with either H or OH radicals, however, produces transient spectra with, in all cases, a well defined peak (∼ 400 nm) and a shoulder (∼ 300 nm) on the end absorption. The decay kinetics at 400 nm are second order, whereas they are first order at 300 nm. The two transient species so distinguished are assigned as the 5-yl and 6-yl radical, respectively. The yields of the corresponding pyrimidines are reported with a discussion of the chemistry of the intermediate radicals.