Cubane Pyrolysis: Scaling Bond Polarity with Universal Polynomials

This work gauges an emerging methodical approach to elucidate an intimate multi-correlation between electron reorganizations, most stable molecular configurations, and the topographical description of relevant chemical processes through an indepth reevaluation of the chemical bonding analysis underpinning the cubane pyrolysis mechanism reported by Seif et al. [RSC Adv., 2020, 10, 32730-32739]. A fold-cusp unified model of universal functions for scaling bond polarity is derived from that multi-nexus. The scaling showed that values of the bond polarity index within the interval [0, 10-5] au correspond to the cusp unfolding, while the fold spans over a wider interval, [10-3, ∞) au. Contrary to previous observations, no cusp flag was detected upon re-examining single scissions and double formations/breakages of carbon-carbon bonds in the first step of the reaction mechanism (i.e., cubane → bicyclo[4.2.0]octa-2,4,7-triene), as demonstrated by the determinant of the Hessian matrix at all potentially degenerate critical points of the electron localization function along the intrinsic reaction coordinate. The transannular ring opening featuring the second elementary reaction, bicyclo[4.2.0]octa-2,4,7-triene → 1,3,5,7-cyclooctatetraene, is the only chemical process exhibiting cusp characteristics, underscoring the model’s reliability. The computed thermochemical dataset closely matches the experimental values, highlighting the robustness and accuracy of the derived insights.