Abstract
BackgroundCalculating Abraham descriptors from solubility values requires that the solute have the same form when dissolved in all solvents. However, carboxylic acids can form dimers when dissolved in non-polar solvents. For such compounds Abraham descriptors can be calculated for both the monomeric and dimeric forms by treating the polar and non-polar systems separately. We illustrate the method of how this can be done by calculating the Abraham descriptors for both the monomeric and dimeric forms of trans-cinnamic acid, the first time that descriptors for a carboxylic acid dimer have been obtained.ResultsAbraham descriptors were calculated for the monomeric form of trans-cinnamic acid using experimental solubility measurements in polar solvents from the Open Notebook Science Challenge together with a number of water-solvent partition coefficients from the literature. Similarly, experimental solubility measurements in non-polar solvents were used to determine Abraham descriptors for the trans-cinnamic acid dimer.ConclusionAbraham descriptors were calculated for both the monomeric and dimeric forms of trans-cinnamic acid. This allows for the prediction of further solubilities of trans-cinnamic acid in both polar and non-polar solvents with an error of about 0.10 log units.Graphical abstractMolar concentration of trans-cinnamic acid in various polar and non-polar solvents.
Highlights
Calculating Abraham descriptors from solubility values requires that the solute have the same form when dissolved in all solvents
The statistical fits are very good, and the 20 or 45 log Ps and log Ks values are fitted with a standard deviation (SD) of about 0.1 log units
We have determined Abraham solute descriptors for trans-cinnamic acid using solubility values measured using Open Notebook Science supplemented with values reported in the literature and with values of partition coefficients from the literature
Summary
Calculating Abraham descriptors from solubility values requires that the solute have the same form when dissolved in all solvents. Carboxylic acids can form dimers when dissolved in non-polar solvents. For such compounds Abraham descriptors can be calculated for both the monomeric and dimeric forms by treating the polar and non-polar systems separately. Specific chemical and biological processes that have been described by the basic model include water-to-organic solvent and gas-to-organic solvent partition coefficients [1], blood-to-body tissue/fluid and gas-to-body tissue/fluid partition coefficients [2], skin permeability coefficients [3], median lethal concentrations of organic compounds for toxicity towards specific aquatic organisms [3], nasal pungency thresholds [3], Draize eye irritation scores [3], and the minimum alveolar concentration for inhalation anthesia towards rats [3]. V encodes sized-related solvent-solute dispersion interactions, including a measure of the solvent cavity term that will accommodate the dissolved solute
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