title: A guideline for the identification of environmentally relevant, ionizable organic molecule species.
abstract: An increasing number of organic compounds detected today in the aquatic environment are ionizable and, therefore, partially or permanently charged (ionic) under the pH conditions encountered in these systems. For evaluating their environmental behavior, which strongly depends on the charge state, the identification of functional groups together with their correct assignment of the respective acidic or basic dissociation constants (pKa) is essential. Despite the growing concern and increasing awareness for ionizable compounds, contradicting and/or confusing information regarding their acid/base properties can be regularly found in the literature, especially when complex structures are encountered. Therefore, we provide a simplified, general, and comprehensive guideline for the identification of ionizable functional groups in organic compounds combined with the correct assignment of their respective pKa values. Beside the explicit definition of basic terms, several tables with more than 30 of the most frequently encountered ionizable compound classes, including their typical pKa value ranges are the centerpiece of the proposed procedure. The straight forward application of the guideline is successfully shown for several environmentally relevant compounds as example.
authors.affiliation: Geoscience Centre, Dept. Applied Geology, University of Göttingen, Goldschmidtstr. 3, 37077 Göttingen, Germany.
authors.forename: Mario
authors.initials: M
authors.lastname: Schaffer
authors.affiliation: Geoscience Centre, Dept. Applied Geology, University of Göttingen, Goldschmidtstr. 3, 37077 Göttingen, Germany. Electronic address: Tobias.Licha@geo.uni-goettingen.de.
authors.forename: Tobias
authors.initials: T
authors.lastname: Licha
mesh_terms: D017408:Guidelines as Topic; D007477:Ions / Q000032:analysis; D009930:Organic Chemicals / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D007477:Ions; D009930:Organic Chemicals; D014874:Water Pollutants, Chemical
keywords: Dissociation; Organic acid; Organic base; Organic compounds; Zwitter; pK(a) and pK(b) value