Structure of Salts of 4,6-Dinitrobenzofuroxan¹

A structural reinvestigation of 4,6-dinitrobenzofuroxan by 1H, 13C, and 15N nuclear magnetic resonance

“…From a comparison of the 'H spectra of DNBF and its partially 5-deuterated analog, Brown and Keyes concluded in 1965 that the lower-field doublet of the AX pattern observed in methylene chloride corresponds to H-7 (10). As can be seen in Table 1, our 15N experiments lead us to assign this doublet to H-5 and therefore to raise doubt about the validity of the structural characterization of the hydroxide adduct of DNBF reported by these authors (vide infra) (10 Me2S0 has been a major drawback in our efforts to characterize papers. Our determination that the H A and Hx resonances the dihydrooxazine N-oxide 3 and has led to the present correspond to the H-7 and H-5 protons, respectively, in this study (9).…”

“…This showed that neither of the two possible types of tautomerism from l a to l b (Scheme 1) or l a to l a ' (Scheme 2 with l a ' = l a for unlabelled DNBF) is important. DNBF was thus formulated as l a on the basis that steric, electrostatic, and mesomeric effects are expected to cause the equilibrium l a l b to lie very predominantly on the side of the isomer l a (10,11,14). Interestingly, l a was later found by an X-ray crystallography study to be the structure of DNBF in the solid state (15).…”

“…Changes in the 'H nmr spectra that take place on reaction of DNBF with a large variety of nucleophiles may only be understood in terms of a complexation since they are closely reminiscent of those described in the reactions involving covalent addition of the same nucleophiles to nitroaromatics like 1,3,5-trinitrobenzene (TNB) (1,10,11). Thus, all reactions are accompanied by a considerable shift to high field of one of the resonances forming the AX or AB pattern of DNBF, as anticipated for a change from sp2 to sp3 hybridization at one of the hydrogen-bearing carbons of the carbocyclic ring.…”

“…It is the early comparison by Brown and Keyes of the changes in the 'H spectra brought about by the addition of hydroxide ion to DNBF and its partially 5-deuterated analog in water (10 H-7 in CHzClz (vide supra), which moved to high field, it was concluded that the corresponding adduct had structure 2 a (Nu = OH). This formulation has never been questioned since it agreed with consideration of resonance forms that favor 2 a over 2 6 , and in all subsequent studies D N B F a adducts were characterized as having structure 2 a o n the basis only of the observation of the anticipated AX patterns in ' H nmr (2-5, 7 , 12).…”

Green Primary Explosives

“…[95], but do not perform as well for practical primary explosive applications. The compound has been used in commercial and military initiating items since the 1950s [96], although its exact structure was not determined until later [96]. Despite its practical uses, KDNBF has not been adopted as a universal alternative to lead styphnate.…”