Octanol–Water Partition Coefficients and Aqueous Solubility Data of Monoterpenoids: Experimental, Modeling, and Environmental Distribution

Terpenes and terpenoids encompass one of the most extensive and valuable classes of secondary metabolites. Their ten-carbon-containing oxygenated representatives, monoterpenoids, are the main components of plant essential oils, being widely exploited in the cosmetic, pharmaceutical, and food industrial areas. Due to its widespread use, it is crucial to investigate their environmental distribution. Thus, new water solubility data were obtained for six monoterpenoids ((1R)-(+)-camphor, (S)-(+)-carvone, eucalyptol, (1R)-(−)-fenchone, l-(−)-menthol, and (−)-menthone) at 298.2 and 313.2 K. Furthermore, octanol–water partition coefficients of 12 monoterpenoids (the six mentioned above plus carvacrol, (±)-β-citronellol, eugenol, geraniol, linalool, and thymol) were measured at 298.2 K. The COSMO-RS thermodynamic model and other more empirical approaches were evaluated for the description of the solubilities and partition coefficients, showing reliable predictions. Lastly, the distribution of the monoterpenoids in the different environmental compartments was assessed through an intuitive two-dimensional chemical space diagram based on the physicochemical equilibrium information reported.