Eigenschaften und IR‐Spektrum der Knallsäure HCNO

Abstract

Die nicht explosive Knallsaure ist eine wesentlich starkere Slure als HCN (pKs :< 5; 25"); ihre Saurestarke i s t vergleichbar mit der von HN3. Die Tnfrarotspektren von gasformigem HCNO und DCNO wurden aufgenommen; die Zuordnung der Absorptionen wird durch eine Normalkoordinatenanalyse gestutzt. Die Krdftkonstanten des linearen FormonitriloxidMolekiils H --C T N ~~ 0 werden mit denen ahnlicher Molekiile verglichen. Die isosteren Verbindungen HCNO und NzO zeigen sehr ahnliche Vdlenzkraftkonstanten. Properties and Infrared Spectrum of Fulminic Acid, HCNOThe non-explosive fulminic acid is a considerably stronger acid than HCN (pKa :s 5 ; 25"); its acid strength is similar to that of HN3. Infrared spectra of both HCNO and DCNO in the gas phase were determined; the assignment of the absorption bands is supported by the results of a normal coordinate analysis. The force constants for the linear formonitrile oxide H --C=N--O are compared with those for related linear molecules, and the bonding in HCNO is discussed.

Some Comments on Fulminic Acid (Knallsäure) and a Praise to Heinrich Wieland and his Work on Organic Derivatives of Nitrogen

“…The structure of fulminic acid, which has a long and fascinating history, as formonitrile oxide HCNO was established by us through its IR spectrum , . In our first paper the IR absorption of HCNO at 538 cm –1 was assigned correctly to the CNO bending mode– in comparison with the isosteric NNO .…”

“…The mass spectrum of the polymer of gaseous fulminic acid, which was prepared from an aqueous solution of sodium fulminate was recorded with a JEOL JMS‐700 M Station. Chemical Ionization (CI) with NH 3 , which favors the formation of quasi‐molecular ions.…”

“…In our first paper the IR absorption of HCNO at 538 cm –1 was assigned correctly to the CNO bending mode– in comparison with the isosteric NNO . This assignment was abandoned in favor of the HCN bending, but later confirmed as CNO bending vibration by the couple B. P . and M. Winnewisser , the great experts and pioneers for the spectroscopic properties and structure of HCNO .…”

“…Winnewisser and Bodenseh ascertained the HCNO structure through its microwave spectrum and B. P . and M. Winnewisser recognized fulminic acid as quasilinear molecule, by which also – after long discussions – the at first unexpected IR absorptions ion in the FIR region of HCNO could be assigned as HCN bending rotations , , …”

“…Grundmann ,, Huisgen and Christl , using formohydroximoyl iodide as source for HCNO, and De Sarlo and co‐workers, using trimethylsilanecarbonitrile oxide, splendidly could confirm Wieland's findings and could characterize the dimer of HCNO and the postulated trimeric intermediate for metafulminuric acid through cycloaddition reactions with olefins. In the mass spectrum of a sample of a white solid, which deposited from gaseous fulminic acid (prepared from sodium fulminate and sulfuric acid) we observed the masses of the dimer ( m/z = 86), the trimer ( m/z = 129), and the tetramer ( m/z = 172) of HCNO. Interestingly, besides the mass m/z = 70 was detected, which corresponds to the adduct of fulminic acid with hydrogen cyanide.…”