NEW REACTION OF 4‐CHLORO‐7‐NITROBENZOFURAZAN WITH AMINES AT HIGH LOCAL CONCENTRATIONS

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Abstract
The fluorogenic amine reagent 4‐chloro‐7‐nitrobenzofurazan (CN,3Fz) reacts with amines to give one of two products, or a mixture, depending on the concentration of amine. At low concentration (e.g. 5 times 10‐4 M) of unprotonated amine the normal replacement of the chlorine occurs, giving Λmax˜ 470 nm. At high concentration of unprotonated amine (e.g. 0.5M), a new product, Λmax˜ 380 nm, is produced. At intermediate concentrations, both products are seen. These results were obtained with aqueous ammonia, methylamine and butylamine, and with butylamine in dry hexane. The 380 nm product also is obtained with high local concentrations of amines, such as with [Lys]n at pH 8.5–10 and micellar dodecylamine at pH 9.5. These results are suggested to be analogous to those of very primitive proto‐enzyme systems, by which clusters of small molecules can produce qualitative changes in “metabolism”. Reaction of CNBFz with gelatin gave qualitative evidence for cross‐linking.