Density Functional Calculations on Dissociation Reactions of Radical Anions of 5-Fluorouracil Derivatives

BOROSKY, G. L.; PIERINI, A. B.

Royal Society of Chemsitry

Año: 2005 vol. 6 p. 649 - 649

ragmentation reactions upon electron attachment to 5-fluorouracil with CH2R substituents at N1 have been evaluated by means of density functional calculations. The present results show that electron attachment to R = F, HC=O or CN derivatives follows a stepwise pathway with radical anions as intermediates. For these compounds, the most stable species formed is the p radical anion which bears an unpaired spin density at the C6 =C5–C4 =O p-conjugated system of the uracil ring. Cleavage of the N1–CH2R or N1CH2–R bond of these intermediates proceeds through the mixing of the p and r states by means of proper geometrical fluctuations along the reaction coordinate. No r radical anion could be characterised on any of these r basal potential surfaces. A noticeable decrease in the activation energy for the N1–CH2R bond dissociation was observed for R = H–C=O or CN. Therefore, such derivatives with unsaturated groups positioned vicinal to the N1–C1 bond are identified as targets for