QSRR quantitative structure-chemical

Quantitative structure-chemical reactivity relationships (QSRR). Chemical reactivities involve the formation and/or cleavage of chemical bonds. Examples of chemical reactivity data are equilibrium constants, rate constants, polarographic half wave potentials and oxidation-reduction potentials. 

Kaliszan, R. (2007) QSRR quantitative structure-(chromatographic) retention relationships. Chemical Reviews, 107, 3212-3246. 

Quantitative structure-retention relationships (QSRR) are helpful in elucidation retention mechanisms, for predicting retention indices and estimating some physicochemical properties. Gas chromatographic retention is a phenomenon that is mainly dependent on molecule-stationary phase interactions. Thus, each molecule, at least in theory, will exhibit unique retention characteristics based on its chemical, structural, and electronic properties. 

The retention and the selectivity of separation in RP and NP chromatography depend primarily on the chemistry of the stationary phase and the mobile phase, which control the polarity of the separation systems. There is no generally accepted definition of polarity, but it is agreed that it includes various selective contributions of dipole-dipole, proton-donor, proton-acceptor, tt-tt electron, or electrostatic interactions. Linear Free-Energy Relationships (LFER) widely used to charactaize chemical and biochemical processes were successfiiUy apphed in liquid chromatography to describe quantitative structure-retention relationships (QSRR) and to characterize the stmctural contributions to the retention and selectivity, using multiple linear correlation, such as Eq. 

A different approach to the systematic characterization of stationary phases is the correlation of analyte structure and retention in a given chromatographic system with the help of quantitative structure retention relationships (QSRR), a distinct discipline of linear free energy relationships (LFER). In QSRR, the total retention of an analyte is separated into individual contributions such as dipole-dipole, K-n, acid-base, and hydrophobic interactions. This approach enables strict interrelations on the basis of fundamental mechanistic aspects in order to improve the physico-chemical understanding of chromatographic retention. 

A more complex approach in QSRR is the description of the retention behavior of solutes by a multiparameter equation that includes several descriptors related to different structural properties. Chromatographic retention data must be some function of the chemical structure of solutes, stationary phase and mobile phase, all of them mutually interacting. However, there is no general, strict, canonical nation relating the retention to these variables. Even if the stationary and mobile phases in a given chromatographic system remain constant, still a precise quantitative description of the retention of a series of solutes appears problematic, and the difficulties increase with the diversity of the solutes consider. The problem is also not trivial for homologues. 

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