The exploration of side reactions allowed the uniqueness and kinetic relevance of the primitive cycle to be evaluated while also allowing for the potential discovery of alternative rTCA cycles that run parallel to the primitive cycle. For each off-cycle intermediate, the subset of b2f2 reactions were characterized that converted these species to the next intermediate in the main cycle (i.e., this tested whether the off-cycle intermediates represent a one-reaction detour from the main cycle) or that converted them to the off-cycle intermediates of the next main cycle reaction (i.e, this tested the existence of parallel cycles to the main cycle, blue circles in Fig. ). The inclusion of these additional reactions corresponds to the characterization of all cycles that are parallel to the uncatalyzed rTCA cycle but separated by a b2f2 reaction. The topology of the resulting network forms a torus structure around the main rTCA cycle, where each rTCA intermediate can participate in up to two sequential transformations away from the main cycle. This geometric constraint, defined by the b2f2 reaction limitation, represents the minimal complexity needed to evaluate both direct competing pathways and potential alternative cycles. Successfully localized transition states (black lines in Fig. ) represent kinetically feasible reactions, while unlocalized transition states (grey lines) indicate mechanistically inaccessible pathways. This pattern of accessible and inaccessible pathways defines the kinetic boundaries of the prebiotic reaction network. An example of a b2f2 exploration about one of the reactants within the main rTCA cycle is shown where the main target species are highlighted in green, off-target species are marked in red, and potential parallel cycle species are denoted in blue (Fig. ).