The relative stability of components in a complex dynamic equilibrium mixture can be determined by quantifying a single leftover reference compound
Systems chemistry aims to understand how chemicals behave and interact in complex mixtures rather than in isolation. The determination of a large number of equilibrium constants in such systems relies on the quantification of a large number of products. This is problematic because the analytical protocol (for example, a UV absorbance profile) must be optimized for each product — requiring access to each component in pure form — and because characteristic signals for a particular product in a complex mixture of similar products may be difficult to identify.
Now, Leonard Prins and co-workers from the University of Padova in Italy have developed1 an indirect optical method for performing such an analysis. They illustrate the principle of their method using a series of acyl hydrazones — formed from mixtures of hydrazides and an aldehyde. Rather than attempting to quantify the amounts of various products, they measure the amount of a specific unreacted hydrazide by scavenging it from the mixture with another aldehyde — chosen so that the product of this reaction has a characteristic UV absorbance.
Prins and co-workers used the method to determine the relative thermodynamic stabilities of a mixture of six hydrazones — a system that involves 15 separate equilibrium reactions in concert. The technique may be useful for assessing how such combinatorial libraries adapt to external stimuli.
References
Gasparini, G., Bettin, F., Scrimin, P. & Prins, L. J. Indirect optical analysis of a dynamic chemical system. Angew. Chem. Int. Ed. 10.1002/anie.200900931 (2009).
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Davey, S. Dynamic determination. Nature Chem (2009). https://doi.org/10.1038/nchem.279
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DOI: https://doi.org/10.1038/nchem.279