:Nitrosyl-O-hydroxide
{{DISPLAYTITLE:Nitrosyl-O-hydroxide}}
{{Chembox
| Name = Nitrosyl-O-hydroxide
| ImageFile = Nitrosyl-O-hydroxide.png
| ImageSize =
| ImageAlt = Nitrosyl-O-hydroxide
| IUPACName = Nitrosyl-O-hydroxide
| OtherNames = Hydroperoxynitrene
Isonitrosyl hydroxide
|Section1={{Chembox Identifiers
| CASNo = 877456-58-1
| CASNo_Ref = {{Cascite|changed|{{cite web |title=Hydroperoxyimidogen Selected ATcT enthalpy of formation based on version 1.124 of the Thermochemical Network |url=https://atct.anl.gov/Thermochemical%20Data/version%201.124/species/?species_number=1198 |publisher=Argonne}}}}
| PubChem = 57470747
| StdInChI=1S/HNO2/c1-3-2/h2H
| StdInChIKey=YSVOEFLTELYJNZ-UHFFFAOYSA-N
| SMILES = [N-]=[O+]O}}
|Section2={{Chembox Properties
| Formula = HNO2
| MolarMass = 47.013 g/mol
| Appearance =
| Density =
| MeltingPt =
| BoilingPt =
| Solubility = }}
|Section3={{Chembox Hazards
| MainHazards =
| FlashPt =
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}}
Nitrosyl-O-hydroxide (molecular formula HOON) is an isomer of nitrous acid, which has been experimentally observed in the gas phase.K. N. Crabtree, M. R. Talipov, O. Martinez Jr., G. D. O'Connor, S. L. Khursan, M. C. McCarthy, Detection and structure of HOON: microwave spectroscopy reveals an O−O bond exceeding 1.9 Å, Science 2013 Dec 13;342(6164):1354-1357. {{doi|10.1126/science.1244180}} HOON contains the longest oxygen-oxygen bond thus far observed in any known molecule, measured to be 1.9149 angstroms. There had been speculation about the existence of this molecule, and ab initio calculations have suggested that it might have a stable chemically bonded structure.M. R. Talipov, Q. K. Timerghazin, R. L. Safiullin, S. L. Khursan, No longer a complex, not yet a molecule: a challenging case of nitrosyl O-hydroxide, HOON, J. Phys. Chem. A 2013 Jan 24;117(3):679-85. {{doi|10.1021/jp3110858}}
Structure
The HOON structure was generated by the McCarthy group in a pulsed supersonic expansion of a gaseous mixture of nitric oxide and water vapor diluted with neon. The molecule was detected using Fourier transform microwave spectroscopy. The equilibrium structure of nitrosyl-O-hydroxide in the gas-phase was determined to be a planar structure, adopting a trans conformation. The structure shown below is a semi-empirical structure derived from a combination of experimental data and theoretically derived vibration-rotation constants.
:
| class="wikitable" style="text-align:center;" |
| dimensions of the trans form (from the microwave spectrum) |
Early theoretical work had suggested the HOON structure should be extremely unstable, decomposing with no significant activation barrier into hydroxyl radical and nitric oxide:T. Fueno, K. Yokoyama, S. Takane, Electronic structure and the unimolecular reactions of imine peroixde HNOO, Theoretica chimica acta 1992 82(3-4) 299-308.
:HOON → OH + NO