Vacuum pyrolysis of N,N-dimethyl bicyclo[3.2.0]hepta-3,6-dien-1-amine — He I ultraviolet photoelectron spectroscopic and computational studies

The photoelectron spectra of N,N-dimethylbicyclo[3.2.0]hepta-3,6-dien-1-amine (1) and its pyrolysate were obtained using an unique ultraviolet (UV) photoelectron (PE) spectrometer interfaced with a CW CO2 laser. Pyrolysis of 1 in the source chamber of the PE spectrometer initially generates the transient N,N-dimethylcyclohepta-1E,3Z,5Z-trien-1-amine (2) - the computed barrier is 21.5 kcal mol(-1) - that isomerizes to the all-cis isomer with a barrier of only 5.0 kcal mol(-1). There is no evidence for the formation of N,N-dimethycyclohepta-1Z,3E,5Z-trien-1-amine (4), formation of which has an zero-point-energy corrected barrier of 28.4 kcal mol(-1). A PE spectrum of an authentic sample of N,N-dimethylcyclohepta-1Z,3Z,5Z-trien-1-amine (3) correlated well with the pyrolysis spectrum. Molecular orbitals and their energies were obtained with Becke3LYP calculations.