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. 2001 Feb 27;98(5):2194-8.
doi: 10.1073/pnas.041481598.

On the acidity and reactivity of HNO in aqueous solution and biological systems

M D Bartberger  1 , J M Fukuto, K N Houk
Affiliations

On the acidity and reactivity of HNO in aqueous solution and biological systems

M D Bartberger et al. Proc Natl Acad Sci U S A. .

Abstract

The gas phase and aqueous thermochemistry and reactivity of nitroxyl (nitrosyl hydride, HNO) were elucidated with multiconfigurational self-consistent field and hybrid density functional theory calculations and continuum solvation methods. The pK(a) of HNO is predicted to be 7.2 +/- 1.0, considerably different from the value of 4.7 reported from pulse radiolysis experiments. The ground-state triplet nature of NO(-) affects the rates of acid-base chemistry of the HNO/NO(-) couple. HNO is highly reactive toward dimerization and addition of soft nucleophiles but is predicted to undergo negligible hydration (K(eq) = 6.9 x 10(-5)). HNO is predicted to exist as a discrete species in solution and is a viable participant in the chemical biology of nitric oxide and derivatives.

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Figures

Figure 1
Figure 1
Plot of experimental versus calculated pKa. Data are listed in Table 2.
Figure 2
Figure 2
Plot of calculated versus experimental hydration equilibria for aldehydes and ketones in Table 3. PCM-B3LYP/6–311+G*+ zero point energy.
Figure 3
Figure 3
Energies of reaction of HNO with nucleophiles and for dimerization (kcal/mol), in the gas phase [B3LYP/6–311+G*+ zero point energy (ZPE)] and in solution (PCM-B3LYP/6–311+G*//B3LYP/6–311+G*+ZPE).
See this image and copyright information in PMC

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