When something goes wrong in the lab, we have to figure out whether it’s a human problem or a chemical problem. Maybe the reaction just doesn’t work, but it’s also possible it wasn’t set up correctly, or analyzed correctly, or purified correctly. Some of the “Troubleshooting (TBSH)” pages list common problems and suggested solutions, like TBSH: Weighing Reactants and Reagents, TBSH: Stirring, TBSH: TLC, TBSH: Workup, TBSH: Column Chromatography, and TBSH: NMR. For more general advice, see My Reaction Failed: FAQ, How to Troubleshoot a Reaction and How to Improve Yield. Finally, In addition to these pages, you can read about how it’s possible for a reaction to fail even when the chemist carries out a written procedure correctly: in a discussion here and examples here.