Abstract: A reaction pathfinder system can leverage historical chemical reaction data and determine a synthesis route in a reaction network. The reaction pathfinder system can account for various performance criteria of chemical reactions such as a highest yield for a molecule or a minimal number of reaction steps. A reaction pathfinder system receives a user request for a synthesis route including one of a user-specified molecule or a user-specified reaction. The reaction pathfinder system may then query a reaction network that has various synthesis routes and represents reactions of reactants to produce respective molecules. The reaction network may be composed of molecule nodes and reaction nodes. The reaction pathfinder system determines, using the reaction network, the synthesis route from the synthesis routes to fulfill the user's request.