Key points are not available for this paper at this time.
Pentazole (cyclo-HN5) is a unique heterocycle categorized as both an organic and inorganic compound. However, attempts to synthesize and characterize cyclo-HN5 have been unsuccessful thus far. In this study, we synthesized a cyclo-HN5 solution and investigated the spectra, structure, aromaticity, acidity, and stability of cyclo-HN5. The lone pair of electrons on the protonated N atom of cyclo-HN5 participates in π-electron delocalization, forming two N═N bonds. Further investigations suggest that cyclo-HN5 exhibits significantly decreased π aromaticity and slightly lower σ aromaticity than cyclo-N5–. Experimental results suggest that pure cyclo-HN5 is unstable at ambient temperatures and pressures, but it can be isolated at high pressures or stabilized in solution by abundant hydrogen bonds. The pKa of cyclo-HN5 was determined as 1.63 (H2O, 25 °C) via potentiometric titration, indicating that cyclo-HN5 is a medium-strong acid. This study reveals the fundamental structure and properties of cyclo-HN5, thereby providing important data for advancing cyclo-HN5 chemistry.
Xia et al. (Mon,) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: