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

Density of CH2Cl2 is 1.33 g/mL H2O CH2Cl2 Mixture of methylene chloride and water Density of CH2Cl2 is 1.33 g/mL H2O CH2Cl2

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

If we dissolve benzoic acid in this mixture in which phase would it concentrate? Salts Neutral organic compounds concentrate in the organic phase

Water CH2Cl2 Salts in water phase Neutral organic compounds in the organic phase CH2Cl2

Treatment of benzoic acid with sodium hydroxide converts it into the salt, sodium benzoate.

Use separatory funnel for separations.

Shake to be sure phases equilibrate Hold stopper and stopcock

Vent frequently

benzoic Acid p-nitroaniline anthracene CH2Cl2 Benzoic acid Anthracene

benzoic Acid anthracene CH2Cl2 NaOH anthracene

HCl Dry filter evaporate weigh Filter wash dry weigh NaOH Dry filter evaporate weigh Filter wash dry weigh Filter wash dry weigh

Addition of acid to the sodium benzoate solution causes benzoic acid to precipitate.

The benzoic acid is filtered, washed, and dried.

Weigh the benzoic acid and measure its melting point.

Cool to complete precipitation

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

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

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

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

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

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

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

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

Grams extracted vs. number of extractions for K = 1, 2 and 4