Nitroxyl and its anion in aqueous solutions: spin states, protic equilibria, and reactivities toward oxygen and nitric oxide.

ABSTRACT: The thermodynamic properties of aqueous nitroxyl (HNO) and its anion (NO(-)) have been revised to show that the ground state of NO(-) is triplet and that HNO in its singlet ground state has much lower acidity, pKa((1)HNO/(3)NO(-)) approximately 11.4, than previously believed. These conclusions are in accord with the observed large differences between (1)HNO and (3)NO(-) in their reactivities toward O(2) and NO. Laser flash photolysis was used to generate (1)HNO and (3)NO(-) by photochemical cleavage of trioxodinitrate (Angeli's anion). The spin-allowed addition of (3)O(2) to (3)NO(-) produced peroxynitrite with nearly diffusion-controlled rate (k = 2.7 x 10(9) M(-1) x s(-1)). In contrast, the spin-forbidden addition of (3)O(2) to (1)HNO was not detected (k << 3 x 10(5) M(-1) x s(-1)). Both

SUBMITTER: Shafirovich V 

PROVIDER: S-EPMC124232 | biostudies-literature | 2002 May

REPOSITORIES: biostudies-literature