Thermolysis of 2,2-dimethoxy-5,5-dimethyl- Δ3- 1,3,4- oxadiazoline studied with photoelectron spectroscopy. He(I) photoelectron spectrum of dimethoxycarbene

Abstract

Gas phase thermolysis of 2,2-dimethoxy-5,5-dimethyl- Δ3-1,3,4-oxadiazoline (1) in an ultraviolet photoelectron spectrometer by means of a CW CO2 laser as directed heat source at 26 W gave a complex PE spectrum that included ionization bands belonging to acetone, tetramethoxyethylene (3), and dimethyl oxalate (4). Subtraction of the spectra of acetone, 3, and 4 from the pyrolysis spectrum of 1 left a simple PE spectrum that is attributed to dimethoxycarbene (2) along with some ethane. ecke3LYP/6-31+G* calculations gave first adiabatic and vertical ionization potentials of 2 as well as orbital energies that are in perfect agreement with experimental values. From the available experimental and calculational data, 2 is assumed to adopt a w conformation.Key words: dimethoxycarbene, 2,2-dimethoxy- Δ3-1,3,4-oxadiazoline, tetramethoxyethylene, He(I) photoelectron spectroscopy, thermolysis.