Showing papers by "Curt Wentrup published in 2019"
TL;DR: This essay deals with the fascinating and highly explosive compounds fulminating gold and fulminated 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.
Abstract: 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.
7 citations
TL;DR: The spectroscopic identification of the nitrene intermediates was aided by calculations at the B3LYP/6-311++G(3df,3pd) level, and the mechanism for their generation in stepwise decompositions of the azides is discussed in the light of CBS-QB3 calculations.
Abstract: Recently, nicotinoyl nitrene (2) has been generated from the photodecomposition of nicotinoyl azide (1) and used as the key intermediate in probing nucleobase solvent accessibility inside cells. Fo...
6 citations
TL;DR: A competing rearrangement of benzonitrile imine forms 3-phenyl-3 H-diazirine, which is a precursor of phenyldiazomethane and hence phenylcarbene, and this reaction is competitive with the ring expansion.
Abstract: Nitrile imines are important intermediates in 1,3-dipolar cycloaddition reactions, and they are also known to undergo efficient, unimolecular rearrangements to carbodiimides via 1 H-diazirines and imidoylnitrenes under both thermal and photochemical reaction conditions. We now report a competing rearrangement, revealed by CASPT2(14,12) and B3LYP calculations, in which C-phenylnitrile imines 8 undergo ring expansion to 1-diazenyl-1,2,4,6-cycloheptatetraenes 12 akin to the phenylcarbene-cycloheptatetraene rearrangement. Amino-, hydroxy-, and thiol-groups in the meta positions of C-phenylnitrile imine lower the activation energies for this rearrangement so that it becomes potentially competitive with the cyclization to 1 H-diazirines and hence rearrange to carbodiimides. The diazenylcycloheptatetraenes 12 thus formed can evolve further to cycloheptatetraene 30 and 2-diazenyl-phenylcarbene 16 over modest activation barriers, and the latter carbenes cyclize very easily to 2 H- and 3 H-indazoles, from which 6-methylenecyclohexadienylidene, phenylcarbene, fulvenallene, and their isomers are potentially obtainable. Moreover, another new rearrangement of benzonitrile imine forms 3-phenyl-3 H-diazirine, which is a precursor of phenyldiazomethane and hence phenylcarbene. This reaction is competitive with the ring expansion. The new rearrangements predicted here should be experimentally observable, for example, under matrix photolysis or flash vacuum pyrolysis conditions.
5 citations
TL;DR: In this paper, photolysis of 2-phenyltetrazole at 266 nm for 0.5 min generates the allenic N-phenylnitrile imine PhN=N(+)=CH(-) 3b, absorbing strongly and cleanly at 2021 cm(-1) in the IR spectrum.
4 citations
TL;DR: Calculations at the B3LYP/6-311G(d,p) level of theory indicate that initial formation of the C-phenylimidoylnitrene 13 and/or benzonitrile imine radical cation 19 is followed by isomerizations of 13•+ to the phenylcyanamide ion 15•+ over a low barrier.
Abstract: Phenylnitrene radical cations m/ z 91, C6H5N, 8a•+ are observed in the mass spectra of 1-, 2-, and 5-phenyltetrazoles, even though no C-N bond is present in 5-phenyltetrazole. Calculations at the B3LYP/6-311G(d,p) level of theory indicate that initial formation of the C-phenylimidoylnitrene 13•+ and/or benzonitrile imine radical cation 19•+ from 1 H- and 2 H-5-phenyltetrazoles 11 and 12 is followed by isomerizations of 13•+ to the phenylcyanamide ion 15•+ over a low barrier. A cyclization of imidoylnitrene ion 13•+ onto the benzene ring offers alternate, very facile routes to the phenylnitrene ion 8a•+ and the phenylcarbodiimide ion 14•+ via the azabicyclooctadienimine 16•+. Eliminations of HNC or HCN from 14•+ and 15•+ again yield the phenylnitrene radical cation 8a•+. A direct 1,3-H shift isomerizing phenylcarbodiimide ion 14•+ to the phenylcyanamide ion 15•+ requires a very high activation energy of 114 kcal/mol, and this reaction needs not be involved. The benzonitrile imine -3-phenyl-1 H-diazirine-phenylimidoylnitrene-phenylcarbodiimide/phenylcyanamide rearrangement has parallels in thermal and photochemical processes, but the facile cyclization of imidoylnitrene 13•+ to azabicyclooctadienimine 16•+ is facilitated by the positive charge making the nitrene more electrophilic. Furthermore, the benzonitrile imine radical cation 19•+ can cyclize to indazole 24•+, and a series of intramolecular rearrangements via hydrogen shifts, ring-openings and ring closures allow the interconversion of numerous ions of composition C7H6N2•+, including 19•+, 24•+, the benzimidazole ion 38•+ and o-aminobenzonitrile ion 40•+, all of which can eliminate either HCN or HNC to yield the C6H5N•+ ions of phenylnitrene, 8a•+, and/or iminocyclohexadienylidene, 34•+. Moreover, benzonitrile imine 19•+ can behave like a benzylic carbenium ion, undergoing a novel ring expansion to cycloheptatetraenyldiazene 45•+. The N-phenylnitrile imine ion 2d•+ derived from 2-phenyltetrazole 1d cleaves efficiently to the phenylnitrene ion 8a•+ but may also cyclize to the indazole ion 24•+. The N-phenylimidoylnitrene 59•+ derived from 1-phenyltetrazole 5d undergoes facile isomerization to the phenylcyanamide ion 15•+ and hence phenylnitrene radical cation 8a•+.
4 citations
TL;DR: In this paper, the faszinierenden and hochexplosiven Verbindungen Knallgold and Knallsilber, die leicht mittels Behandlung von in Konigswasser gelostem Gold with Ammoniak bzw. durch Reaktion von Silberoxid oder Silbersalzen with ammoniak hergestellt werden konnen.
Abstract: Dieser Essay beschreibt die faszinierenden und hochexplosiven Verbindungen Knallgold und Knallsilber, die leicht mittels Behandlung von in Konigswasser gelostem Gold mit Ammoniak bzw. durch Reaktion von Silberoxid oder Silbersalzen mit Ammoniak hergestellt werden konnen. Insbesondere Knallgold hat im 16. bis 18. Jahrhundert die Alchemisten gefesselt. Zahlreiche Herstellungen wurden beschrieben, und viele Versuche wurden unternommen, destillierbares, sublimierbares oder trinkbares Gold zu erzeugen und die so erhaltenen Produkte (wahrscheinlich meistens Goldchloride) zur Herstellung einer Tinktur zu verwenden, die “unreine” Metalle saubern und in Gold transformieren konnte und ebenfalls ein Wunderheilmittel aller menschlichen Krankheiten sein sollte.
2 citations
TL;DR: Calculations at the B3LYP/6-311G(d,p) level have revealed facile H-transfer from the tetrazole to the pyridine ring in 2-(5-tetrazolyl)pyridine, 12a•+ → 21•+, taking place in the radical cations.
Abstract: 5-Phenyltetrazole 1e is an important source of phenylnitrene or the phenylnitrene radical cation ( m/ z 91) under thermal, photochemical, and electron impact conditions. Similarly, 3- or 4-(5-tetrazolyl)pyridines 12b,c yield pyridylnitrene radical cations 9a•+ ( m/ z 92) upon electron impact. In contrast, 2-(5-tetrazolyl)pyridine 12a•+ generates 2-pyridyldiazomethane 24•+ and 2-pyridylcarbene 26•+ radical cations ( m/ z 119 and 91) upon electron impact. The 2-pyridylcarbene radical cation undergoes a carbene-nitrene rearrangement to yield the phenylnitrene radical cation. Calculations at the B3LYP/6-311G(d,p) level have revealed facile H-transfer from the tetrazole to the pyridine ring in 2-(5-tetrazolyl)pyridine, 12a•+ → 21•+, taking place in the radical cations. Subsequent losses of N2 generate the pyridinium diazomethyl radical 22•+ or pyridinium-2-carbyne 23•+. These two ions can isomerize to 2-pyridyldiazomethane 24•+ and 2-pyridylcarbene 26•+, the latter rearranging to the phenylnitrene radical cations 9a•+. 13C-labeling of the tetrazole rings confirmed that 2-(5-tetrazolyl)pyridine 12a generates 2-pyridylcarbene/phenylnitrene radical cations retaining the 13C label, but 4-(5-tetrazolyl)pyridine 12c generates 4-pyridylnitrene 18c•+, which has lost the 13C label. 2-Pyridylcarbene/phenylnitrene radical cations ( m/ z 91) also constitute the base peak in the mass spectrum of 1,2,3-triazolo[1,5- a]pyridine 34. Similarly, 4-pyridylnitrene radical cation 18c•+ or its isomers ( m/ z 92) is obtained from 1,2,3-triazolo[1,5- a]pyrazine 36. Several other α-heteroaryltetrazoles behave in the same way as 2-(5-tetrazolyl)pyridine, yielding heteroarylcarbene/arylnitrene radical cations in the mass spectrometer, and this was confirmed by 13C-labeling in the case of 1-(5-tetrazolyl)isoquinoline 42-13C. In general, 5-aryltetrazoles generate arylnitrene radical cations under electron impact, but α-heteroaryltetrazoles generate α-heteroarylcarbene radical cations.
2 citations
TL;DR: In this article, the authors describe their 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.
Abstract: 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.
2 citations
TL;DR: Photolysis of 2,3-diazidonaphthalene-1,4-dione in methyltetrahydrofuran matrices forms 1 in argon matrices verifies that 32 forms 33, as confirmed by electron paramagnetic resonance spectroscopy.
1 citations
TL;DR: In this paper, the authors proposed a method to solve the problem of the problem: the one-dimensional graph.
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TL;DR: In this article, the authors proposed a method to solve the problem of the problem: the one-dimensional graph.
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