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Trichloroisocyanuric Acid (TCCA) based on deoximation of a coumarin oxime

A new chloramine signaling probe, based on a coumarin oxime, was developed. The coumarin oxime 1 exhibited efficient off–on type fluorescent signaling behavior toward trichloroisocyanuric acid (TCCA) in an aqueous acetonitrile solution. The signaling is due to the TCCA-assisted transformation of the oxime function to its carbonyl analogue. The presence of common metal ions and anions did not interfere with the TCCA signaling of this probe. Probe 1 was found to be useful for the sensitive determination of the concentration of the practical oxidant TCCA in an aqueous environment, with a detection limit of 7.58*10-7 M.
Among the organic chloramines, in particular, trichloroisocyanuric acid (TCCA) and sodium N-chloro-p-toluenesulfonamide (chloramine-T) have become increasingly important. Chloramines are inorganic or organic nitrogen compounds, which contain one or more chlorine atoms attached to the nitrogen atoms. They are inexpensive, stable in aqueous solution, and environmentally benign oxidants that are broadly used both in daily life and for industrial applications. Because they are easier to handle than chlorine gas or metal hypochlorites, they are widely used in the purification of drinking water and as sanitizing agents in swimming pools. Chloramines are also commonly used in synthetic reactions. The usefulness of chloramines arises from the fact that they behave as a source of both a halonium ion and various nitrogen-containing species. As a result, these reagents can react with a wide range of functional groups, leading to a number of molecular transformations such as chlorination of alkenes and aromatics, oxidation of ethers and alcohols, epoxidation of alkenes, and nitrosation of amines. In organic syntheses, hypochlorites could also be substituted with N-chloramines, especially when anhydrous conditions are necessary.
The oxime derivative of ethoxycoumarin exhibited a pronouncedly sensitive fluorogenic signaling behavior toward the industrially important chloramine trichloroisocyanuric acid (TCCA)  in aqueous acetonitrile solution. Protection of carbonyl functions by converting them to oximes is one of the most useful tactics in organic synthesis. In this case, deprotection of oximes to form carbonyls could be effected by a variety of oxidation and reduction reactions. Recently, a broad range of N-halosulfonamides has been reported for the regeneration of carbonyl compounds from oximes. We devised a new reaction-based probe for the convenient determination of practical oxidant chloramines by using the oxime-carbonyl transformation.