The Quench
A Perfect Reaction
: No quench is necessary
A Nightmare Scenario
: The product mixture is highly reactive and requires dropwise addition of quenching reagent to prevent a volcano-like
exothermic eruption.
Common Rookie Mistakes:
Running Reactions
Step by Step:
- Quench at the temperature recommended, at the rate recommended.
- If gas is evolved during the quench, or it is otherwise exothermic, watch the reaction carefully to be sure it is
under control.
- If you notice that quenching the reaction is exothermic, cool the flask with an ice bath.
- Quench
only when your TLC or other analysis method indicates that the reaction is complete. Beginning students
often simply trust the literature time period, and never check their expereiment. Experimentals in the literature
do not always give accurate reaction times, and if your compound is slightly different, it will react at a different
rate.
- Remember that quenching with aqueous solution at low temperature will result in formation of ice--so don't panic
when precipitate forms. Let the reaction warm up (and the ice melt) before continuing with the workup.
- If possible, work up the reaction immediately after quenching it.
See Also: