Quantitative structure–retention relationship modelling of esters on stationary phases of different polarity

Molecular Interactions in Chromatographic Retention: A Tool for QSRR/QSPR/QSAR Studies

“…The excess charge of these atoms leads to electrostatic interactions that are stronger than the weak dispersive dipolar interactions. For esters, all these factors were included in the calculation of the retention index through a small increase in the SET i values for heteroatoms and the carbon atoms attached to them (Souza et al, 2009b). As in the case of ketones and aldehydes, it was verified that the introduction of the dipole moment of the molecule is not sufficient to explain the chromatographic behavior of these molecules.…”

“…The semi-empirical topological index (I ET ) allowed the creation of a new descriptor, the electrotopological index, I SET , which was recently developed by our group and applied to QSPR studies to predict the chromatographic retention index for a large number of organic compounds, including aliphatic hydrocarbons, alkanes and alkenes, aldehydes, ketones, esters and alcohols (Souza et al, , 2009a(Souza et al, , 2009b(Souza et al, , 2010. The new descriptor for the above series of molecules can be quickly calculated from the semi-empirical, quantum-chemical, AM1 method and correlated with the approximate numerical values attributed by the semiempirical topological index to the primary, secondary, tertiary and quaternary carbon atoms.…”

“…This new index, I SET , is able to distinguish between the cis-and trans-isomers directly from the values for the net atomic charges of the carbon atoms that are obtained from quantumchemical calculations . For polar molecules like aldehydes, ketones, esters and alcohols, the presence of heteroatoms like oxygen changes considerably the charge distribution of the corresponding hydrocarbons, leading to a small increase in the interactions between the solute and the stationary phase (Souza et al, 2009a(Souza et al, , 2009b(Souza et al, , 2010). An appropriate way to calculate the I SET was developed, taking into account the dipole moment exhibited by these molecules and the atomic charges of the heteroatoms and the carbon atoms attached to them.…”

Development of semi‐empirical electrotopological index using the atomic charge in QSPR/QSRR models for alcohols

“…As in the case of ketones, aldehydes [30] and esters [31] we have included the above-mentioned points by calculating the retention index as in Equation (1), also using Equation (2) for heteroatoms, but including slight alterations that incorporated the effects of the dispersive dipolar interactions. For alcohols, the major effects in the charge distribution are due the presence of the oxygen atom and they occur at the site of and close to their neighbor (adjacent carbon atoms).…”

“…In order to obtain a molecular descriptor not directly related to the chromatographic retention indices (RI) but based on values calculated by quantum mechanics, a new semi-empirical electrotopological index (I SET ) was developed [29][30][31]. This new approach takes into account the dipole moment exhibited by these molecules as well as the atomic charges of the heteroatoms and the carbon (www.interscience.wiley.com) DOI: 10 atoms attached to them through the definition of an equivalent local dipole moment.…”