Acetylene (<10%) a Ethene (>50%) b Propene (40%) Allene (90%) d Propyne (81%) Electronic structure of C 2 H 4 O has been extensively studied before. The ISC has been studied by Bowman and co-workers, by surface-hopping, and by Klippenstein and co-workers, by non-adiabatic transition-state theory (NA-TST) and dynamical simulations. While most these ISC calculations were carried out for only a single triplet surface, Ref. 15 considered the contribution to the rate from 2 triplet states. The simulations revealed that ISC in Cvetanović diradicals can indeed be very effective and showed that different treatments of ISC yield different kinetic predictions at high temperature. In this work we explore the qualitative differences between the electronic structure of several Cvetanović diradicals and evaluate important trends and features relevant to ISC. We focus on general trends rather than on quantitative rates modeling. The paper outline is as follows. In the next section, we describe molecular orbital (MO) framework and the nature of relevant electronic states. Section 3 outlines theoretical methods employed and computational details. Results of electronic structure calculations as well as their implication for kinetics are presented in Section 4.