In the pharmaceutical industry, there is tremendous awareness of the effect that pH can have on the biological activity of a compound. Obviously, the pH determines the chemical “state” in which the compound will exist, which in turn, affects its properties. For example, the solubility of a compound, as well as its permeability, just to name a few parameters, can vary greatly as a function of pH. However, when I search a chemical database for a given structure, how should pH be taken into account? For example, if I structure search for acetic acid, should “acetate” be included in my search results? Do any of the major chemical databases today allow one to specify that results be restricted by pH?

I remember one early chemical database that didn’t support the Kekulé delocalized depiction of aromatic rings. The database required that individual double bonds be drawn. When performing a search, the database wasn’t sophisticated enough to give you all “chemically” equivalent results, so that if you didn’t search for both alternate forms, you might miss a result. Based on my very limited understanding of InChi, it has the potential to resolve these kinds of issues in rather facile way.