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.

Highlighting the Underrated Side of the High Profile Nitroso Entity as a Nucleophile

“…o ‐Quinone β‐Nitrosomethides (N‐ o QMs) of type VII or VIII encompass both the nitrosoalkene and the o ‐quinone methide ( o ‐QM) V or VI motifs (Figure 2b). [63–67,72–78] …”

Pressure-induced hydrogen transfer and polymerization in crystalline furoxan

“…4 Therefore, studying its structure, properties, and synthesis is important to develop other electron-rich furoxan derivatives. Although some experimental 5,6 and theoretical investigations [7][8][9][10] have been done on furoxan, many fundamental and practical problems are still not well understood because it possesses a complex chemical behavior. For instance, its behavior under high pressure is unknown until now.…”

Comparative Theoretical Studies of Energetic Substituted Carbon- and Nitrogen-Bridged Difurazans

“…Therefore, they can help design better and more efficient laboratory tests. To our knowledge, besides many experimental researches about the furazan and furoxano , derivatives theoretical calculations have been performed to investigate their heats of formation and detonation properties. ,,, However, there is still lacking systematic and comprehensive molecular design for difurazan-based HEDMs.…”