- Photolysis of matrix-isolated acetyl bromide and the infrared spectrum of the 1:1 molecular complex of hydrogen bromide with ketene in solid argon
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Ketene and HBr were generated by photolysis of acetyl bromide in argon matrix.Of the photolysis products, ketene and HBr were trapped in the same matrix cage to form 1:1 molecular complex.The HBr stretching mode in the complex was observed at 2396 cm-1, which was displaced to 160 cm-1 below the frequency of the monomer HBr fundamental in solid argon.The DBr stretching frequency in the ketene-d2-DBr complex produced on photolysis of acetyl bromide-d3 was observed at 1717 cm-1, which was displaced to 120 cm-1 below the frequency of the monomer DBr fundamental in solid argon.After the matrices were annealed, these absorptions were shifted to 2383 and 1708 cm-1, respectively.
- Kogure, N.,Hatakeyama, R.,Suzuki, E.,Watari, F.
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- Kinetics of the Reactions of Alkyl Radicals (CH3, C2H5, i-C3H7, and t-C4H9) with Molecular Bromine
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The gase-phase kinetics of the reactions of four alkyl radicals (CH3, C2H5, i-C3H7, and t-C4H9) with molecular bromine have been studied over the temperature range 296-532 K.The reactions were isolated for quantitative study in a heatable tubular reactor coupled to a photoionization mass spectrometer.Radicals were homogeneously generated in the reactor by pulsed photolysis of suitable precursor molecules at 193 or 248 nm.The subsequent decays of the radical concentration in the presence of different Br2 concentrations were monitored in time-resolved experiments.Rate constants were obtained at five temperatures.The Arrhenius expressions (k = A exp(-E/RT)) that describe the temperature dependencies of the measured rate constants of the R + Br2 -> RBr + Br reactions are as follows 3 molecule-1 s-1), E/(kcal mol-1)>: R = CH3 ; R = C2H5 ; R = i-C3H7 ; R = t-C4H9 .The trend in the measured rate constants and the results of prior studies of the dynamics of the CH3 + Br2 reaction indicate that the reactivity of R + Br2 reactions is determined largely by long-range attractive forces and not by reaction thermochemistry.
- Timonen, R. S.,Seetula, J. A.,Gutman, D.
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- Syntheses and15N NMR Spectra of Iminodiaziridines - Ring-Expansions of 1-Aryl-3-iminodiaziridines to 1H- and 3aH-Benzimidazoles, 2H-Indazoles, and 5H-Dibenzo[d,f] [1,3]diazepines
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Iminodiaziridines are synthesized, by (i) 1,3-dehydrochlorination with potassium, teri-butoxide of N-chloroguanidines, generated in situ from. N,N′,N″-substituted guanidines with tert-butyl hypochlorite, and (ii) base-mediated 1,3-elimination of sulfuric acid from N,N',N″- substituted hydroxyguanidine O-sulfonic acids. At elevated temperatures, (alkylimino)diaziridines undergo valence isomerization by 1,3shift, [2+1] cycloelimination to afford isocyanides and diazenes, and ring-opening elimination to yield alkylideneguanidines. N′-Aryl-N-hydroxyguanidine O-sulfonic acids furnish (N-arylimino)diaziridines, but no 1-aryl-3- iminodiaziridines, instead giving rearranged isomere. Precursors containing perdeuterated feri-butyl groups give rearranged products that show complete scrambling. This indicates that l-aryl-3iminodiaziridines are intermediates that undergo very rapid I degenerate valence isomerization. Provided that the ortho aryl positions are substituted, high yields of (arylimino)diaziridines are obtained, along with 2-imino-2,3-dihydro-3aHbenzimidazoles, Otherwise, 2-amino-lH-benzimidazoles and strongly fluorescent 3-amino-2H-indazoles, originating from rearrangements of the elusive l-aryl-3-iminodiaziridines, predominate. N',N″-Diaryl-N-hydroxyguanidine O-sulfonic acids give only rearranged products: a 2-amino-1H-benzimidazole and a 6-amino-5H-dibenzo[d,f][1. 3]diazepine if aryl = phenyl, or a 2-imino-2,3-dihydro-3aH-benzimidazole if aryl = mesityl. 3aH-Benzimidazoles slowly dimerize through Diels-Alder reactions. 15N NMR signals were assigned, to the syn and anti ring nitrogen atoms of iminodiaziridines with the help of a combination of homonuclear NOE and HNHMBC or HN-gHMBC experiments.
- Quast, Helmut,Ross, Karl-Heinz,Philipp, Gottfried,Hagedorn, Manfred,Hahn, Harald,Banert, Klaus
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supporting information; experimental part
p. 3940 - 3952
(2010/03/01)
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