ISSN:
0009-2940
Keywords:
Electronic structure
;
PE spectroscopy
;
Gas-phase thermolysis
;
4H-Pyrazoles, 3,s-dihydro-
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Gas-phase thermolyses of the 3,5-dihydro-4 H-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 0x0- and iminocyclopropanes. At higher temperatures and in flash vacuumpyrolysis, 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 identification 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.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19901230533
