- Flash vacuum pyrolysis and photolysis of 3,3,5,5-tetramethylpyrazolin-4- one - A matrix isolation study
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The flash vacuum pyrolysis of 3,3,5,5-tetramethylpyrazolin-4-one (4) with subsequent trapping of the products in argon at 10 K results in the formation of a complex product mixture with tetramethylcyclopropanone (5) as one of the minor constituents. The 193 nm photochemistry of matrix-isolated 4 is much cleaner, yielding cyclopropanone 5 and allene oxide 9 as the major products. The reaction of tetramethylallene 13 with oxygen atoms yields the same product mixture of 5 and 9 and thus provides an independent route to these species. The experimental IR spectra of 5 and 9 are in good agreement with the results from DFT calculations.
- Sander, Wolfram,Wrobel, Roman,Komnick, Peter,Rademacher, Paul,Muchall, Heidi M.,Quast, Helmut
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- Gas-Phase Thermolysis of 4-substituted 3,5-Dihydro-3,3,5,5-tetramethyl-4H-pyrazoles Studied by Photoelectron Spectroscopy and Flash Vacuum Pyrolysis
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Gas-phase thermolysis of the 3,5-dihydro-4H-pyrazoles 1-4 have been studied by photoelectron spectroscopy and flash vacuum pyrolysis.In the PE-controlled thermolysis, 1-4 extrude molecular nitrogen, and the fragments cyclize immediately to different three-membered rings.In the case of 2 and 3, the former 4-substituent becomes part of the three-membered ring, whereas 1 and 4 afford short living oxo- and iminocyclopropanes.At higher temperatures and in flash vacuum pyrolysis, acyclic compounds and smaller molecules are formed in a second step.Based on MNDO, AM1, and PM3 calculations, the ionization potentials of 3,5-dihydro-3,3,5,5- tetramethyl-4-methylene-4H-pyrazole (3) have been assigned to molecular orbitals.To aid the identificaion of the pyrolysis products, PE spectra of the methylenethiirane 9 and the methylenecyclopropanes 11 and 13 have been measured and interpreted with the aid of SCF calculations.
- Kindermann, Markus K.,Poppek, Rainer,Rademacher, Paul,Fuss, Andreas,Quast, Helmut
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p. 1161 - 1168
(2007/10/02)
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