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How to Remove Water From Nitromethane With Dry Ice

The purification of solvents, such as nitromethane, is essential for synthetic chemists in both research and industrial settings. Nitromethane is useful as a solvent because of its weak proton affinity when compared with other polar solvents. Unfortunately, the liquid is highly susceptible to contamination by impurities such as propionitrile, copper and silver. These impurities and any water molecules that are mixed into the nitromethane must be removed before the solvent can be used safely.

Nitromethane sample
Diethyl ether
Dewar flask
Dry ice
Stir bar
Stir plate
Thermometer
Buchner funnel
Vacuum pump
Glass rod
Distilling flask
Vacuum distillation column

Instructions

- 1
  Mix the nitromethane with an equal volume of diethyl ether in a Dewar flask.
- 2
  
  A thermometer will ensure that the mixture is cold enough.
  
  Add a clean stir bar to the mixture and secure the flask to a stir plate, equipped with a thermometer.
- 3
  Add powdered dry ice slowly to reach a temperature of -60 degrees Celsius. Allow the mixture to stir for five minutes at this low temperature.
- 4
  Transfer the mixture to a Buchner funnel packed with dry ice and pump off the ether, leaving crystals of nitromethane.
- 5
  Pack the crystals tightly into the funnel with a glass rod and rinse twice more using diethyl ether that has been cooled to -78 degrees Celsius.
- 6
  
  A round-bottom flask can be used for distillation.
  
  Remove the dry ice and allow the nitromethane to melt through the filter into a distillation flask.
- 7
  Vacuum distill the nitromethane to 101 degrees Celsius, discarding the distillate. The dry solvent should be used immediately or stored in a dark container.

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