A kinetic study on the reactivity of azanone (HNO) toward its selected scavengers: Insight into its chemistry and detection

Abstract

Recently, azanone (HNO), which is the protonated one-electron reduction product of ^·NO, has gained considerable attention due to its unique pharmacological effects. Although there has been much progress in understanding HNO biology and chemistry, it remains the most elusive reactive nitrogen species. Herein, we applied the competition kinetics method, based on two parallel HNO reactions with the different scavengers and molecular oxygen (k_O2 = (1.8 ± 0.3) × 10⁴ M^-1 s^-1), to determine the rate constants for the reactions of HNO with its selected co-reactants. The rate constants for the reactions of HNO with nitrite (k = (5.0 ± 0.9) × 10³ M^-1s^-1), hydroxylamine (k = (2.1 ± 0.4) × 10⁴ M^-1s^-1), sulfite (k = (1.2 ± 0.2) × 10⁶ M^-1 s^-1), thiosulfate (k = (2.2 ± 0.7) × 10⁴ M^-1 s^-1), benzenesulfinate (k = (4.4 ± 0.9) × 10⁴ M^-1 s^-1), 2-bromobenzenesulfinate (k = (5.0 ± 1.2) × 10⁴ M^-1 s^-1), nitrosoglutathione (k = (2.4 ± 0.7) × 10⁴ M^-1s^-1), nitrosobenzene (k > 1.5 × 10⁵ M^-1 s^-1), 2-nitroso-1-naphthol (k = (1.0 ± 0.2) × 10⁶ M^-1 s^-1), triphenylphosphine (k > 7.3 × 10⁶ M^-1 s^-1), triphenylphosphine-3,3',3″-trisulfonate (k = (3.0 ± 0.5) × 10⁶ M^-1 s^-1), tris-carboxyethylphosphine (k = (1.2 ± 0.3) × 10⁷ M^-1 s^-1), a triphenylphosphine-based P-CM fluorogenic probe (k > 1.2 × 10⁷ M^-1 s^-1), the TEMPO-9-AC fluorogenic probe (k = (9 ± 2) × 10⁴ M^-1 s^-1) and 4-acetamido-TEMPO (k = (8 ± 2) × 10⁴ M^-1s^-1) are reported. The implications of these HNO reactions are also discussed. The data presented in this paper are a valuable contribution to the incompletely understood reactivity of HNO.

Keywords: Angeli's salt; Azanone; Nitroso compounds; Phosphines; Piloty's acid.