The First Chemical Achievements and Publications by Justus von Liebig (1803−1873) on Metal Fulminates and Some Further Developments in Metal Fulminates and Related Areas of Chemistry

CHNO - Formylnitrene, Cyanic, Isocyanic, Fulminic, and Isofulminic Acids and their Interrelationships at DFT and CASPT2 Levels of Theory

Fulminic and cyanic acids played a decisive role in the conception of isomerism 200 years ago. Cyanic (HOCN), isocyanic (HNCO), and fulminic (HCNO) acids have been detected in several interstellar sources, but isofulminic acid (HONC) is little known. Here we examine the interrelationships between the four acids and formylnitrene, HC(O)N, at the CASPT2 and three DFT levels. Formylnitrene has a triplet ground state, T0, a closed shell singlet (CSS), S0, and an open-shell singlet (OSS), S1, lying ∼7 and 27 kcal/mol above T0, respectively. The CSS is weakly stabilized by a 12 kcal/mol bond between the N and the O atoms. A conical intersection 12 kcal/mol above T0 permits easy T0-S0 interchange. Formyl azide and formylnitrene (T0 and S0) are isomerized thermally to HNCO. HOCN is best obtained via dissociation of the nitrene (or of HNCO) to H• + NCO• radicals ∼46 kcal/mol above the T0 nitrene. Isofulminic acid, HONC, isomerizes readily to cyanic acid, HOCN, in thermal and photochemical reactions. Fulminic acid, HCNO, can isomerize to HNCO via CSS formylnitrene. Easy tautomerization prevents the preparation of HOCN in quantity. The barrier to isomerization is strongly reduced in small hydrogen-bonded aggregates so that trace amounts of HOCN can exist in equilibrium with HNCO.

Synthesis and Stability of Ammonium Selenocyanate [NH4][SeCN] and Its Reactivity toward Ag[SeCN]

[NH₄][SeCN] and Ag[SeCN] were synthesized by salt metathesis starting from the respective chlorides and K[SeCN]. Both products were fully characterized by single-crystal and powder X-ray diffraction, differential scanning calorimetry-thermogravimetric analysis (DSC-TGA), and solid-state IR and Raman spectroscopy. Quantum-mechanical calculations allowed for detailed assignment and interpretation of vibrational spectra. For dissolved [NH₄][SeCN], nuclear magnetic resonance spectra were collected. High-temperature powder X-ray diffraction (HT-PXRD) allowed for the analysis of the thermal behavior of solid [NH₄][SeCN]. Furthermore, the reaction of [NH₄][SeCN] with Ag[SeCN] leads to the formation of the ternary salts [NH₄][Ag(SeCN)₂] and [NH₄]₃[Ag(SeCN)₄]. The structures of the latter were determined from single-crystal X-ray diffraction (SC-XRD) data, and bulk analysis was performed by Rietveld refinement, Raman spectroscopy, and elemental analysis.

Fulminating Gold and Silver

This Essay deals with the fascinating and highly explosive compounds fulminating gold and fulminating silver, which are easily made by treatment of gold dissolved in aqua regia with ammonia, and by reaction of silver oxide or silver salts with ammonia, respectively. Fulminating gold in particular captivated the alchemists in the 16th to 18th centuries. Numerous preparations were described, as well as numerous attempts to make volatile, sublimable or distillable gold, and to use the products so obtained (which were most likely gold chlorides) to make the sought-after tincture, which would "heal" the "impure" metals and transform them into gold, and equally be a panacea to cure all human illnesses.

Nitrogen- and Sulfur-Containing Energetic Compounds. 64 Years of Fascinating Chemistry

This essay details the author’s work with high-energy molecules based on sulfur or nitrogen, or both, which started with amateur rocket propellants like zinc dust and sulfur followed by experiments with the highly sensitive compounds nitrogen trichloride and fulminating gold. Research on the inorganic and organic fulminates and the isomeric cyanates led to detailed investigations of reactive intermediates generated by flash vacuum pyrolysis or photolysis, in particular nitrenes and carbenes derived from azides, diazo compounds, triazoles, and tetrazoles and characterized in low temperature matrices.