Creating new molecules is one of the toughest tasks in chemistry. Whether the goal is a life-saving drug or a cutting-edge material, each compound must be built through a carefully planned series of reactions. Mapping out these steps requires deep expertise and strategic thinking, which is why chemists often spend years mastering the process.

A major hurdle is retrosynthesis. In this approach, chemists begin with the final molecule they want and work backward to figure out simpler starting materials and possible reaction routes. This involves many decisions, such as selecting the right building blocks, deciding when to form rings, and determining whether sensitive parts of the molecule need protection. While computers can scan enormous "chemical spaces," they still struggle to match the strategic judgment of experienced chemists.

Another challenge involves reaction mechanisms, which describe how reactions proceed step by step through the movement of electrons. Understanding these mechanisms allows scientists to predict new reactions, improve efficiency, and avoid costly trial and error. Although current computational tools can suggest many possible pathways, they often lack the intuition needed to pinpoint the most realistic ones.