SOP: Jones Oxidation for Triptycene-9-Carboxaldehyde

Precautions1:

Chromium trioxide is a strong oxidizer and will readily start fires with alcohols and is incompatible with almost all organic compounds.

Toxic substance, wash affected area immediately. May cause cancer through inhalation, targets lungs and kidneys3.

Handling CrO3 requires the use of all standard laboratory PPE(gloves, lab coat, safety glasses). CrO3 should be handled in a hood at all times.

Preparation2 and use for the oxidation of triptycene-9-carboxaldehyde:

Note: For every one equivalent of chromium trioxide two oxidations can be done. Use only ¾ of an equivalent for this specific reaction to cut down on the amount of chromium trioxide handled/used.

  1. Very slowly add the H2SO4 to cold distilled water continuously stirring in an ice bath. For every 1 mL of H2SO4 use roughly 5 mL of water.
  2. Add one equivalent amount of chromium trioxide (CrO3) (1 mL : 1 g) to the diluted sulphuric acid (H2SO4) solution (Jones reagent) in a slow manner keeping the mixture cooled in an ice bath at all times.
  3. Very slowly add the prepared Jones reagent to an ice-cold stirring mixture of acetone and starting material. Once the entire Jones reagent is added to the mixture let warm to room temperature slowly before refluxing for one hour.
  4. After refluxing, allow the mixture to cool to room temperature and add to cold distilled water. The precipitate is collected by filtration and washed with excess water.
  5. The filtrate should be quenched with sodium carbonate or isopropanol before disposing into liquid waste. To quench excess reagent, add quenching solution slowly as the addition may cause a fire. The excess jones reagent will change color from orange to green indicating a properly quenched solution.
  6. It is important to quench all containers used in making the jones reagent to ensure excess reagent does not get improperly discarded in waste.

Note: CrO3 can be added either to a concentrated H2SO4 solution then diluted with H2O, or to a pre diluted H2SO4 solution.

References:

  1. http://www.sciencelab.com/msds.php?msdsId=9923475
  2. http://www.spms.ntu.edu.sg/cbc/Safety/documents/2012/Jones%20reagent.pdf
  3. http://terpconnect.umd.edu/~choi/MSDS/Sigma-Aldrich/CHROMIUM(VI)%20OXIDE.pdf
Last modified: July 20, 2023