I Can't Reproduce an Earlier Experiment!

If you are having trouble reproducing an experiment (from the literature, or a laboratory notebook: either your own or someone else's.)

Nothing is more frustrating than repeating an experiment that worked before, either for you or someone else, and meeting with failure. Unfortunately, it's very, very common. Here are some ideas for making another chemist's reaction work in your hands:

If no reaction occurs:
  1. Heat it up
  2. Run in at a higher concentration
  3. Add more reagent/catalyst.
  4. Purify your reagents
  5. Distill your solvent
  6. Use a rigorously anhydrous/oxygen-free environment (degas the solvent, use Schlenkware for setup/transfers, azeotrope your substrate with benzene)
If reaction occurs, but does not give as good a result as recorded:
  1. Is the reaction scale the same? Sometimes results vary significantly depending on reaction scale, so try the experiment on exactly the same scale as the original procedure.
  2. Add more of key reagents, sometimes the written amount in notebooks is not accurate (often people add a slight (or even sizable) excess without noting it.
  3. Monitor the reaction, and stop it as soon as possible. Sometimes the reaction time given is not accurate, and if exact times weren't recorded, people estimate generously. Leaving a reaction too long can lead to decomposition.
  4. Stir vigorously. Ineffective mixing can give poor results.
  5. Consider reaction temperature. Is the reaction flask maintaining the appropriate temperature? Sometimes adding reagents spikes the temperature, or addition of reagents at too slow or two fast a rate can affect reaction temperature. This is especially true if you’re working on a scale smaller than the original prep.
  6. Consider the order of addition of reagents, and the rate of addition of reagents. These variables can be very important, yet sometimes procedures are missing detailed explanations.
Common reasons people have trouble reproducing experimental results:
  1. The quality or identity of the reagents or solvents is not identical to the original conditions.
  2. Something in the procedure was not written down by the original experimentalist.
  3. The original experiment did not work as stated in the written account.