title: Synthesis, spectroscopy and structure of the parent furoxan (HCNO)2.
abstract: The parent furoxan (1,2,5-oxadiazole 2-oxide), synthesized from glyoxime and NO(2)(g), has been investigated in the gas phase for the first time by mid-infrared and He I photoelectron spectroscopy, and in the liquid phase by Raman spectroscopy. The ground-state geometry has been obtained from quantum-chemical calculations at the B3LYP, MPn (n = 2-4), CISD, QCISD, CCSD, CCSD(T), RSPTn (n = 2,3), MRCI, and MR-AQCC levels using 6-311++G(2d,2p), cc-pVTZ, aug-cc-pVTZ, cc-pCVTZ, and cc-pVQZ basis sets. Furoxan is predicted to be planar, with a strong exocyclic and a relatively weak endocyclic N-O bond. The furoxan moiety is electron rich, indicated e.g. by a large negative NPA charge (-0.46 e). According to various aromaticity indices, furoxan is nearly as aromatic as furan and furazan. Unlike alkyl- and cyano-substituted furoxans, the parent furoxan, upon thermolysis, does not cleave to the monomer nitrile oxide, yielding only HNCO, HCN, CO(2), CO, NO, and H(2)O decomposition products.
authors.affiliation: Department of Inorganic Chemistry, Institute of Chemistry, Eotvos Lorand University Budapest, H-1117 Budapest, Pazmany P. setany 1/A, Hungary. pasinszki@chem.elte.hu
authors.forename: Tibor
authors.initials: T
authors.lastname: Pasinszki
authors.forename: Balázs
authors.initials: B
authors.lastname: Havasi
authors.forename: Balázs
authors.initials: B
authors.lastname: Hajgató
authors.forename: Nicholas P C
authors.initials: NP
authors.lastname: Westwood