Theoretical Study of the Internal Rotation of the Hydroxylic Group of the Enol Form of Guanine

Abstract

Emphasis was placed in the present work on a density functional theory and Hartree−Fock study of the internal rotation of the hydroxylic group of the enol form of guanine. This was achieved by monitoring the behavior of energy, chemical potential, hardness, electrophilicity, and polarizability along the torsional coordinate. An energy barrier of about 9.5 kcal/mol was found about midway between two stable planar conformations. The analysis of the behavior of reactivity descriptors shows that the principles of maximum hardness and minimum polarizability are satisfied. Very good linear relations have been established between energy, chemical potential, hardness, and electrophilicity power allowing the characterization of the rotational process in terms of the simultaneous change of these global properties.

Caracterización de la reactividad intrínseca de los halobencenos en el modelo conceptual de la teoría de funcionales de la densidad (TFD)

“…24,25 La Ecuación 5 presenta un problema de discontinuidad en áto-mos y moléculas cuando se combina con la aproximación de diferencias finitas, dando lugar a tres expresiones de FF. (6) En el punto r, f + (r) mide la reactividad para un ataque nucleofílico, f -(r) mide la reactividad para un ataque electrofílico y f°(r) describe un ataque por un radical y se obtiene como el promedio aritmético de f + (r) y f -(r). La cuantificación de la función es posible a través de un esquema de condensación sobre una región atómica, se pueden escribir las FF usando las técnicas de análisis poblacional; 26,27 esto da lugar a las siguientes ecuaciones de trabajo: (7) donde q k (N) denota la población electrónica del átomo k del sistema de referencia, más correctamente denominado q k (N 0 ).…”

“…Esta herramienta ha sido usada para probar varios sistemas moleculares. [5][6][7][8] El estudio teórico en el modelo de la Teoría de Funcionales de la Densidad, puede ayudar como una guía en la reactividad de los halobencenos. La Teoría de Funcionales de la Densidad es un modelo conceptual para relacionar los cálculos con conceptos tales como potencial químico electrónico (μ), 9-12 dureza química (η) 9-13 y electrofilicidad (ω), 14 conceptos que nos ayudan a entender el comportamiento electrónico de los sistemas.…”

Is There a Minimum Electrophilicity Principle in Chemical Reactions?

“…It is shown that ω is a useful descriptor for reactivity and is frequently used in analysis of chemical reactivity of different molecules. [28][29][30][31][32][33][34][35][36][37][38][39] Variations of this quantity during molecular vibrations, 40,41 internal rotations, 42,43 and chemical reactions 40,[44][45][46][47][48][49] have been recently studied. Chamorro et al 40 found that under constants μ and ( ) r ν , there would be a minimum electrophilicity principle along a reaction path.…”

Comparative study of kinetics and reactivity indices of free radical polymerization reactions

“…Following the PMH principle, molecular systems at equilibrium tend toward states of higher hardness, and, as a consequence, transition states are expected to present a minimum hardness value [4]. This principle was confirmed for the isomerization reaction of guanine, and good linear correlations between the rotational energy of the hydroxyl group and the chemical potential, hardness, and electrophilicity index along the reaction path were established [5].…”