Leaving the Lab
Not Voodoo Home
It is reasonable to leave the laboratory:
- If your reaction has been stirring at a constant temperature for one hour and is less than 25% complete
- If you have successfully run the reaction before and know it can be left safely
- If your reaction proceeds under mild conditions at room temperature and you have checked it twice by TLC
It is not reasonable to leave the laboratory:
- During time-sensitive steps (reaction, quench, and workup)
- In the middle of column chromatography
- If unstable compounds are not stored properly
Repercussions of leaving an experiment unattended:
- Solvent evaporated during refluxing due to a poor seal.
- Stirring stopped.
- Reaction became heterogeneous during slow addition, complicated mixing.
- Slow addition mechanism stopped, so reagent was not added to the flask properly.
- The desired reaction occurred cleanly, but then (a) a byproduct started to form, so the reaction appears to be nonselective (b) the product decomposed under the reaction conditions.
- Unwanted fluctuation of temperature
- You forgot to add a reagent or miscalculated, and no reaction occured at all. You could have corrected the problem, but you didn't notice in time.
- You don't know how long the reaction took.
- You don't know if the reagent was consumed at the same rate as the substrate, or if it just gradually decomposed on its own.
- You will not see the formation of intermediates, which can be an important indication of reaction progress.