Observed Acidities of Charcoals, Clays, and Common Laboratory Purification Reagents in Aqueous and Organic Solutions

摘要

In studying the purification and clarification of organic compounds with mixtures of charcoals, clays, and chromatography supports in organic solution, we noted that the observed pH of the resulting slurry was an important factor in determining which of the materials was appropriate. To examine this aspect of these purification methods, we determined the observed acidity of several commercially available reagent-grade clays, decolorizing agents, chromatography supports, and several common laboratory drying reagents in water and in several organic solvents. As expected, we found that clays, decolorizing carbons, and filter aids cannot be assumed to be pH neutral and nonreactive with organic molecules. For the purification of organic compounds with pH-sensitive functionalities, the potential acidity or basicity of a clarification reagent in the chosen solvent should be considered.