The crystal structure of the σ-complex of 4,6-dinitrobenzofuroxan and potassium 2-nitropropenide

A crystalline σ-complex (4d) of 4,6-dinitrobenzofuroxan and potassium 2-nitropropenide has been prepared and characterized by single-crystal X-ray analysis. There are two K+ and two independent anionic 2-nitropropane DNBF moieties per asymmetric unit. A cis-configuration of the hydrogen and NO2 substituents is observed. This structure determination suggests a syn-elimination process for the loss of nitrous acid from 4d which readily occurs in Me2SO solution to give the carbanion (6d) of 4,6-dinitro-7-methylbenzofuroxan.