In order to predict the energies of the low-lying electronic states of the dioxa derivative of trimethylenemethane (DOTMM), we have carried out (U)B3LYP, CASPT2, and (U)CCSD(T) calculations, using the aug-cc-pVTZ basis set. Our calculations predict that DOTMM has a triplet ground state, with one unpaired electron occupying a b2 σ MO and the other a b1 π MO. An open-shell singlet state, with the same orbital occupancy as the triplet, is calculated to lie very close to the 3A2 ground state. However, this open-shell singlet (1A2) is predicted to be the transition structure for methylene rotation and to lead to the barrierless formation of an equivalent pair of α-lactones. We also report the results of some calculations on the fragmentation of DOTMM to CH2 + CO2. Our predictions about DOTMM could be tested experimentally by generating the DOTMM•− radical anion in the gas phase and obtaining its negative ion photoelectron spectrum.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Organic Chemistry