- The main reason for recrystallisation is to increase the yield of certain reductions by removing any unreacted aldehydes in this case benzaldehyde, if you are working with amounts >0.5 mole, then we recommend at least one recrystallisation, although it is not essential.
- It is a simple process and product losses are less than 5% instead of the more usual 20 to 25% loss in many organic chemistry recrystallisations.
- PPE: Ideally wear a pair of disposable nitrile gloves underneath a pair of butyl gauntlets, at a minimum two pairs ofdisposable nitrile gloves.
- Recrystallise using 99.5%+ isopropanol at 60 °C / 140 °F (no higher).
- Add P2NP at 2 g / ml of isopropanol (even though alot more can dissolve in 1 ml isopropanol, purity would be reduced).
- Once dissolved, hot filter any undissolved contaminants if required, filter through your buchner funnel using a fast filter paper or higher porosity frit and have a little additional isopropanol already at 60 °C / 140 °F to rinse any crystals on filter/frit, then cover your erlenmeyer flask with film or foil with a couple of small air holes either side.
- Allow to cool to room temperature then place in refrigerator for an hour before filterinf the crystals that will have formed.
- The filtrate (mother liquor) can then be placed in a freezer for a few hours to recover more product.
- Ideally use a Buchner funnel with fast filter paper or higher porosity frit to filter the pale yellow crystals, return filtrate to freezer for additional crops, then rinse with ice-cold isopropanol (save this filtrate for future rinses, and collect crystals formed within it from time to time), finally rinse with distilled water to remove any catalyst and allow to vacuum dry in funnel for 10 minutes (the water filtrate is disposed of).
- There should be no orange crystals or red product - rinsing with ice-cold isopropanol will remove any outer layers of red polymerised product.
- The above procedure is repeated another couple of times to be able to achieve a purity of 99%.
- Finally vacuum dry crystals in buchner funnel for 15 minutes, once dry, weigh crystals and carefully transfer to an air-tight PP container and place in cold storage.
The warmer the storage temperature the quicker nitrostyrene's polymerize. Viable crystals can be stored in a refrigerator (0 to 5 °C / 30 to 40 °F) for 6 months, or a freezer (-5 to -15 °C / 20 to 5 °F) for 2 years or more.
If you do not have a buchner funnel and vacuum source, then you will have to gravity filter, using beaker that a funnel can sit on, place 2 coffee filters and pour crystal and IPA mixture in, now place everything in a refrigerator to filter and then dry before storing.
All Rights Reserved. ¤
Eidolon Chemical Services Ltd.
¤ © 2021