Did I Successfully Obtain Crystals in My Organic Lab Experiment?

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SUMMARY

The discussion centers on the crystallization process of (1-R, 2-S) ephedrine and mandelic acid in an organic lab setting. The user initially mixed the compounds in 6 mL of 95% ethanol but inadvertently added 10 mL of methylene chloride, which hindered crystal formation. After boiling off the solvent and cooling the solution on ice, the user successfully obtained crystals. The user seeks confirmation on the identity of the crystals and expresses concern about potential redissolution at room temperature.

PREREQUISITES
  • Understanding of organic chemistry principles, specifically crystallization techniques.
  • Familiarity with solvents such as ethanol and methylene chloride (DCM).
  • Knowledge of the properties of (1-R, 2-S) ephedrine and mandelic acid.
  • Experience with laboratory equipment, including Erlenmeyer flasks and glass rods for prodding.
NEXT STEPS
  • Research the crystallization process of organic compounds, focusing on cooling techniques.
  • Learn about the melting point determination of organic crystals to confirm compound identity.
  • Study the effects of solvent mixtures on crystallization outcomes.
  • Investigate best practices for storing organic crystals to prevent redissolution.
USEFUL FOR

This discussion is beneficial for organic chemistry students, laboratory technicians, and researchers involved in crystallization experiments and compound identification.

Haftred
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In organic lab this week we were mixing (1-R, 2-S) ephedrine with mandelic acid to get crystals. I dissolved both compounds in 6 mL 95% EtOH and then poured them together. After cooling + glass prodding I should have had no trouble getting crystals. HOWEVER, during the cooling I accidently added about 10 mL of methylene chloride to the mixture, and was unable to get crystals at room temp. I knew DCM has a low boiling point so I just boiled off all of the solvent and added 12 mL of EtOH 95%. I then re-heated the soln and let it cool. I prodded the sides with a glass rod and still nothing. Then I decided to put the soln (it was in a 100 ml erlenmeyer) on ice. Before you know it I had crystals. Can I be confident that these are the crystals of the resulting compound when ephedrine and mandelic acid are reacted?

Once I got crystals I stored them in my drawer for next week at room temp. It seems nobody else needed ice, so I'm worried that everything will be redissolved when I get back.

Thanks.
 
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A lot of things can happen with boiling , I would take some melting point data of the sample.
 
You want to carefully cool the sample... not shock it with ice. If you are unsure about your procedure, just remove a few crystals of what you have and reheat the whole thing. Once it has slowly come to room temperature, add the crystals and pray to whatever deity you worship.

Good luck.
 

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