| Abstract
| - Large scale chemical reaction networks are a ubiquitous phenomenon, from the metabolism of living cellsto processes in planetary atmospheres and chemical technology. At least some of these networks exhibitdistinctive global features such as the “small world” behavior. The systematic study of such properties,however, suffers from substantial sampling biases in the few networks that are known in detail. Acomputational model for generating them is therefore required. Here we present a Toy Model that providesa consistent framework in which generic properties of extensive chemical reaction networks can be exploredin detail and that at the same time preserves the “look-and-feel” of chemistry: Molecules are representedas labeled graphs, i.e., by their structural formulas; their basic properties are derived by a caricature versionof the Extended Hückel MO theory that operates directly on the graphs; chemical reaction mechanisms areimplemented as graph rewriting rules acting on the structural formulas; reactivities and selectivities aremodeled by a variant of the Frontier Molecular Orbital Theory based on the Extended Hückel scheme. Theapproach is illustrated for two types of reaction networks: Diels−Alder reactions and the formose reactionimplicated in prebiotic sugar synthesis.
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