Extractions - University of Illinois Archives Archives/1505050... · If K = 1.0, a = 10 grams, S2 =...
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Extractions Mixture of benzoic acid, anthracene, and p-nitroaniline
Transcript of Extractions - University of Illinois Archives Archives/1505050... · If K = 1.0, a = 10 grams, S2 =...
Extractions
Mixture of benzoic acid, anthracene, andp-nitroaniline
COHO
NH2
NO2
Mixture of methylene chloride and water
Density of CH2Cl2 is 1.33 g/mL
CH2Cl2
H2O
If we dissolve NaCl in this mixturewhich phase has the highest saltconcentration?
Salts concentrate inthe water layer
If we dissolve benzoic acid in thismixture in which phase would itconcentrate?
Neutral organiccompounds concentrate inthe organic phase
Salts
Salts in water phase
Neutral organiccompounds in theorganic phase
Water
CH2Cl2
COOH + Na OH COO Na
Benzoic Acid Sodium Benzoate
Treatment of benzoic acid withsodium hydroxide converts itinto the salt, sodium benzoate.
COOH + Na OH COO Na
NH3 + HCl NH4+ Cl-
Base Acid Salt
NH2O2N + HCl NH3O2N Cl
Use separatory funnel for separations.
Shake to be surephases equilibrate
Hold stopperand stopcock
benzoic Acid
p-nitroaniline
anthracene
HCl CH2Cl2
NH3O2N ClBenzoic acid
Anthracene
benzoic Acid
anthracene
NaOH CH2Cl2
COO Na anthracene
NH3O2N Cl COO Na
NH2O2N
NaOH
COOH
Filterwashdryweigh
HCl
Filterwashdryweigh
Dryfilterevaporate
weigh
Addition of acid tothe sodiumbenzoate solutioncauses benzoic acidto precipitate.
The benzoic acid isfiltered, washed,and dried.
Weigh the benzoicacid and measure itsmelting point.
NH2O2NNH3O2N ClNaOH
Cool to complete precipitation
Dry the methylene chloride solutionof anthracene with a small amountof sodium sulfate.
Remove the drying agent by filtrationthrough a fluted filter paper.
Evaporate themethylene chlorideon a steam bath.
Use an invertedfunnel connected tothe vacuum line tocollect the vapor.
Weigh your products and measuretheir melting points.
Put your samples in labeled vialsand give them to your TA.
10 g t-butyl alcohol100 mL ether100 mL water
Partition Coefficients
2.2 = x g / 200 mL
( 10 - x)g /100 mL
x = 8.1 grams
10 grams t-butyl alcohol
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 gramsSecond extraction with 100 mL yields 2.5 gramsTotal 2 extractions with 100 mL = 7.5 grams
Grams extracted vs. number of extractionsfor K = 1, 2 and 4
