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

Structures

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

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

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

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

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

Distribution

NH3 + HCl NH4+ Cl- Salt Base Acid

Distribution

Use separatory funnel for separations.

Shake to be sure phases equilibrate Hold stopper and stopcock

Vent frequently

benzoic Acid p-nitroaniline anthracene HCl CH2Cl2 Benzoic acid Procedure

benzoic Acid anthracene NaOH CH2Cl2 anthracene Procedure

HCl NaOH Dry filter evaporate weigh Filter wash dry weigh Procedure

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

The benzoic acid is filtered, washed, and dried. Filter, wash, dry

Weigh the benzoic acid and measure its melting point. Weigh, mp

Cool to complete precipitation

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

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

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

Put your samples in labeled vials and give them to your TA. 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

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