Background: Calculating 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.

Results: Abraham 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.

Conclusion: Abraham 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.