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Extractions

Extractions. Mixture of benzoic acid, anthracene, and p-nitroaniline. Mixture. Methylene Chloride and Water. Density of CH 2 Cl 2 is 1.33 g/mL. H 2 O. CH 2 Cl 2. Add Salt. If we dissolve NaCl in this mixture which phase has the highest salt concentration?.

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Extractions

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  1. Extractions Mixture of benzoic acid, anthracene, and p-nitroaniline

  2. Mixture

  3. Methylene Chloride and Water Density of CH2Cl2 is 1.33 g/mL H2O CH2Cl2

  4. Add Salt If we dissolve NaCl in this mixture which phase has the highest salt concentration? Salts concentrate in the water layer

  5. Add Benzoic Acid If we dissolve benzoic acid in this mixture in which phase would it concentrate? Salts Neutral organic compounds concentrate in the organic phase

  6. Phases Salts in water phase Water Neutral organic compounds in the organic phase CH2Cl2

  7. Sodium Benzoate Treatment of benzoic acid with sodium hydroxide converts it into the salt, sodium benzoate. Benzoic Acid Sodium Benzoate

  8. Salts in Water Phase

  9. Ammonia and Acid NH3 + HCl NH4+ Cl- Salt Base Acid

  10. Aniline and Acid

  11. Separatory Funnel Use separatory funnel for separating liquid phases.

  12. Shake to be sure phases equilibrate Hold stopper and stopcock

  13. Vent frequently

  14. Extract with HCl benzoic Acid p-nitroaniline anthracene HCl CH2Cl2 Benzoic acid Anthracene

  15. Extract with NaOH benzoicAcid anthracene NaOH CH2Cl2 anthracene

  16. Extraction Summary HCl NaOH Dry filter evaporate weigh Filter wash dry weigh Filter wash dry weigh

  17. Precipitate Benzoic Acid Addition of acid to the sodium benzoate solution causes benzoic acid to precipitate.

  18. Purify Benzoic Acid The benzoic acid is filtered, washed, and dried.

  19. Weight, m.p. Weigh the benzoic acid and measure its melting point.

  20. Precipitate p-Nitroaniline Cool to complete precipitation

  21. Dry Methylene Chloride Dry the methylene chloride solution of anthracene with a small amount of sodium sulfate.

  22. Filter Remove the drying agent by filtration through a fluted filter paper.

  23. Remove Methylene Chloride Evaporate the methylene chloride on a steam bath. Use an inverted funnel connected to the vacuum line to collect the vapor.

  24. Weigh your products and measure their melting points. Put your samples in labeled vials and give them to your TA.

  25. Partition Coefficients 10 g t-butyl alcohol 100 mL ether 100 mL water

  26. 10 grams t-butyl alcohol x g / 200 mL 2.2 = ( 10 - x)g / 100 mL x = 8.1 grams

  27. Which is better? Extract once with 200 mL or twice with 100 mL?

  28. If K = 1.0, a = 10 grams, S2 = 100 mL Extract once with 200 mL yields 6.7 grams Extract once with 100 mL yields 5.0 grams Second extraction with 100 mL yields 2.5 grams Total 2 extractions with 100 mL = 7.5 grams

  29. Grams extracted vs. number of extractions

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