Consequences of one-electron oxidation and one-electron reduction for 4-aminopyrimidine--DFT studies.
The consequences of one-electron oxidation and one-electron reduction were studied for 4-aminopyrimidine (4APM), which displays prototropic tautomerism. Since experimental techniques are incapable of detecting less than 0.1% of minor tautomers, quantum-chemical calculations [DFT(B3LYP)/6-311+G(d,p)] were carried out for all possible tautomers of neutral 4AMP and its redox forms, 4APM (+ •) and 4APM (- •). Four tautomers were considered: one amine and three imine tautomers (two NH and one CH form). Geometric isomerism of the exo = NH group was also taken into account. One-electron oxidation (4APM - e → 4APM  (+ •)) has no significant effect on the tautomeric preferences; it influences solely the composition of the tautomeric mixture. The amine tautomer is favored for both 4APM  (+ •) and 4APM. An interesting change in the tautomeric preference occurs for 4APM (- •). One-electron reduction (4APM + e → 4APM (- •)) favors the C5 atom for the labile proton. The preference of the imine CH tautomer in the tautomeric mixture of 4APM (- •) may partially explain the origin of CH tautomers in nucleobases.
Department of Chemistry, Warsaw University of Life Sciences (SGGW), ul. Nowoursynowska 159 c, 02-776, Warsaw, Poland. ewa_raczynska@sggw.pl
Ewa D
ED
Raczyńska
Katarzyna
K
Kolczyńska
Tomasz M
TM
Stępniewski
D003198:Computer Simulation; D005609:Free Radicals / Q000737:chemistry*; D007536:Isomerism; D008958:Models, Molecular; D010084:Oxidation-Reduction; D011743:Pyrimidines / Q000737:chemistry*; D011789:Quantum Theory; D013816:Thermodynamics
D005609:Free Radicals; D011743:Pyrimidines; C034821:4-aminopyrimidine