Kinetic Study on the Reactivity of Azanone (HNO) toward Cyclic -Nucleophiles.

Azanone (HNO) is an elusive electrophilic reactive nitrogen species of growing pharmacological and biological significance. Here, we present a comparative kinetic study of HNO reactivity toward selected cyclic -nucleophiles under aqueous conditions at pH 7.4. We applied the competition kinetics method, which is based on the use of a fluorescein-derived boronate probe FlBA and two parallel HNO reactions: with the studied scavenger or with O ( = 1.8 × 10 Ms). We determined the second-order rate constants of HNO reactions with 13 structurally diverse -nucleophiles ( = 33-20,000 Ms). The results show that the reactivity of HNO toward -nucleophiles depends strongly on the structure of the scavenger. The data are supported with quantum mechanical calculations. A comprehensive discussion of the HNO reaction with -nucleophiles is provided.