PHOTOELECTRON-SPECTRA OF GEMINAL VINYL-DISUBSTITUTED AND ETHYNYL-DISUBSTITUTED CYCLOPROPANE DERIVATIVES

The He(I) photoelectron (PE) spectra of 1,1-divinylcyclopropane (1), (Z,E)- and (Z,Z)-1,1-di-1-propenylcyclopropane (2 and 3), 1,1-diethynylcyclopropane (4), 1-ethynyl-1-propynylcyclopropane (5), 1-ethynyl-1-vinylcyclopropane (6), and (Z)-1-(1-propenyl)-1-(propynyl)cyclopropane (7) have been recorded. The interpretation of the first bands of the PE spectra is based on the comparison with related compounds and on the results of MO calculations. For the calculations on 1-7 the MNDO method, and in case of 1, 4, and 6 an ab-initio procedure with a 3-21 G basis has been applied. The investigations show that 1, 2, 6, and 7 prefer the bisected conformation while in 3 the propenyl groups are strongly twisted. Our studies reveal also that the three-membered ring shows relais properties and interacts strongly with both pi-systems.