Effects of the ionization in the tautomerism of uracil: A reaction electronic flux perspective.
The one-step tautomerization processes of uracil and its radical cation and radical anion have been investigated in the light of the reaction force and reaction electronic flux (REF) formalisms. The relative energies of the different tautomers as well as the corresponding tautomerization barriers have been obtained through the use of the G4 high-level ab initio method and by means of B3LYP/6-311+G(3df,2p)//B3LYP/6-311+G(d, p) calculations. Systematically, the enol radical cations are more stable in relative terms than the neutral, due to the higher ionization energy of the diketo forms with respect to the enolic ones. Conversely, the enol radical anions, with the only exception of the 2-keto-N1 anion, are found to be less stable than the neutral. The effects of the ionization are also sizable on the tautomerization barriers although this effect also depends on the particular tautomerization process. The reaction force analysis shows that all reactions are mainly activated through structural rearrangements that initiate the electronic activity. This electronic activity is monitored along the reaction coordinate through the REF that obeys a delicate balance between the acid and basic character of the atoms involved in the hydrogen transfer.
Departamento De Química C-13, Universidad Autónoma De Madrid, Cantoblanco, 28049, Spain, Madrid.
Al Mokhtar
AM
Lamsabhi
Facultad De Química, Nucleus Millennium Chemical Processes and Catalysis (CPC), Laboratorio De Química Teórica Computacional (QTC), Pontificia Universidad Católica De Chile, Santiago, Chile.
Soledad
S
Gutiérrez-Oliva
Departamento De Química C-13, Universidad Autónoma De Madrid, Cantoblanco, 28049, Spain, Madrid.
Otilia
O
Mó
Facultad De Química, Nucleus Millennium Chemical Processes and Catalysis (CPC), Laboratorio De Química Teórica Computacional (QTC), Pontificia Universidad Católica De Chile, Santiago, Chile.
Alejandro
A
Toro-Labbé
Departamento De Química C-13, Universidad Autónoma De Madrid, Cantoblanco, 28049, Spain, Madrid.
Manuel
M
Yáñez
D004583:Electrons; D007477:Ions / Q000737:chemistry; D011789:Quantum Theory; D014498:Uracil / Q000737:chemistry*
D007477:Ions; D014498:Uracil
acidity and basicity; density functional theory (DFT); electronic reaction flux; hydrogen transfer; tautomerism; uracil