Polarity characterization of gas-chromatographic stationary phase on base of theoretical description of intermolecular interactions. II. Case of H-bonds

Abstract

The goal of this article is the development of a new method of classification of chromatographic
stationary phases (SP) on the fundamental basis. In this paper known approaches Keesom and Debye, which
are supplemented by conclusions of the theory of generalized charges (TGC) and quantum-mechanical
estimates of the parameters of the hydrogen bond. Generalized charge (GC) is a function of the number, state
function, and distance from the point of interaction of the valence electrons of the molecule. TGC was a key
instrument to describing the adsorption and create a method in general. With it derived an expression for the
energy of intermolecular interactions, which comprises three independent members: one member - a
characteristic of the non-polar energy determined generalized charges; the second - the characteristic polar
forces associated with the presence of dipole moments in at least one of the interacting objects; third - the
characteristic hydrogen bond depends on the probability of its formation. Condition of their interaction is
dependent on the equilibrium distance corresponding to the minimum of the total energy.
We derive the relative characteristics of the polar forces and hydrogen bonds, called «polarity» and
«hydrophilicity», respectively. Polarity parameter is the ratio of the square of the dipole moment to GC.
Hydrophilicity parameter is the ratio of the probability of formation of a hydrogen bond to the GC. Thus, SP
parameters comprise two independent quantities - polarity and hydrophilicity.
To determine the characteristics of the SP used experimentally found Kovats’ indices and their
relationship with the adsorption energy, found by TGC. Developed SP characterization technique requires
data on Kovats’ indices of at least two molecules with different polarity and hydrophilicity