Experiment 6:
EXTRACTION of ANALGESICS
Objectives
To learn the techniques of acid-base extraction, drying organic solvents, and vacuum filtration.
To separate aspirin from acetaminophen using the extraction technique.
To determine the efficiency of separation and the purity of compounds using HPLC analysis.
Before coming to lab…
Watch the following videos to help you understand the techniques that will be used. Extractionhttp://www.wonderhowto.com/how-to/video/how-to-do-a-liquid-liquid-
extraction-in-the-chemistry-lab-259811/view/
Vacuum Filtrationhttp://video.google.com/videoplay?docid=-
4541453194468704643#docid=1104445520143750871
Drying Organic Solventshttp://www.wonderhowto.com/how-to/video/how-to-dry-an-organic-solution-
in-the-chemistry-lab-259802/view/
ACTIVE INGREDIENTS— GOODY’S POWDERS
OH3C
O
O
O
N
O
HCH3
OH
Aspirin 2-Acetylsalicylic acid
MF: C9H8O4
MW: 180.2 g/mol
mp: 138-140 oC
Hazards: Toxic, Irritant
pKa: ~3.5
Solubility in H2O: 1g in 300mL @ 21oC
Acetaminophen
4-acetamidophenol
MF: C8H9NO2
MW: 151.2 g/mol
mp 169-172oC
Hazards: Toxic, Irritant
pKa: ~10
Solubility in H2O:1g in 150 mL at 21oC
H
500 mg/powder 325 mg/powder
ACID–BASE EXTRACTION—CHEMICAL EQUATIONS
CO
O H+ Na+ , HCO3
- (aq) + H2CO3
Carboxylic acid Organic soluble, water insoluble
Sodium carboxylate Organic insoluble, water soluble
H2O + CO2(g)
HCl(aq)
Carboxylic acid Organic soluble, water insoluble
OCH3
O
CO
O,- Na
+
OCH3
O
CO
O H
OCH3
O
NH
CH3
OH
O
+ Na+ , HCO3- (aq) NO REACTION
Acetaminophen remains soluble in the organic phase and insoluble in the aqueous phaseAcetaminophen
Organic soluble, water insoluble
ACID–BASE EXTRACTION FLOW CHART
2 Goody's Powders25 mL Ethyl Acetate25 mL sat. NaHCO3
Combined aqueous layers (aspirin salt)
Organic layer(acetaminophen)
1. 6M HCl2. Filter
Aspirinaqueous filtrate = waste
1. dry over MgSO42. filter3. evaporate
Acetaminophen
Separatory funnel
aqueous layer (aspirin salt)
Organic layer(acetaminophen)
re-extract with 10% NaHCO3re-extract with ethyl acetate
USING A SEPARATORY FUNNEL
• Be sure the stopcock is in the horizontal position (closed) before adding any liquid!
• Be sure the stopper is tightly sealed before inverting!
• Always keep one finger on the stopper!
VACUUM FILTRATION TECHNIQUE
• Always clamp the suction flask to a ring stand!
• Run the red vacuum hose to the yellow vacuum line to pull suction! To vacuum
line…
DRYING ORGANIC SOLVENTS
• Add a small amount of MgSO4 to the organic solution and swirl.
• If the MgSO4 continues to clump and sink to the bottom, continue to add.
• If the MgSO4 settles out of solution slowly (like a snow globe), the solution is dry.
OVERVIEW
Perform acid/base extraction using separatory funnel.
Isolate ASPIRIN and ACETAMINOPHEN in separate flasks.
A O
ACETAMINOPHEN (O)
ASPIRIN SALT (A)
OVERVIEWACETAMINOPHEN…
Dry organic layer with MgSO4.
Suction filter to remove MgSO4 from liquid.
Evaporate liquid on hotplate.
Reweigh to obtain final weight & calculate % recovery.
Dissolve solid in REAGENT acetone.
Submit HPLC sample.
Transfer to large sample vial and submit to instructor until next lab period.
OVERVIEW ASPIRIN…
Add acid to recover solid aspirin.
Suction filter to recover solid aspirin.
Submit HPLC sample.
Secure aspirin in large filter paper and submit to instructor until next lab period.
NEXT LAB PERIOD… Obtain final weight of aspirin.
Calculate % recovery.
Prepare sample for melting point analysis.
THEORETICAL RECOVERY
For this experiment, we dissolved 2 Goody’s powders in 25 mL of ethyl acetate.
In each Goody’s powder, there is 0.500 g of aspirin and 0.325 g of acetaminophen.
Theoretical Recovery: 0.500 g per powder X 2 powders = ? g of Aspirin 0.325 g per powder X 2 powders = ? g of Acetaminophen
PERCENT RECOVERY
After the product has been dried sufficiently, the ACTUAL YIELD can be determined.
In theory, you should be able to recover 100% of each compound, however this is not always the case.
In order to determine the success of your recovery, the percent yield is calculated as follows: Percent recovery : actual recovery (g)
X 100 theoretical recovery (g)
Table 6.1: Experimental Results
Aspirin Acetaminophen
Theoretical recovery after extraction (g)
calculated calculated
Actual recovery after extraction (g)Obtain weight
next lab!Obtain weight
this lab!
% Recovery after extraction calculated calculated
Table 6.2: HPLC Results
Compound
HPLC retention times (min) and area %
Standards
Aspirin Sample
AcetaminophenSample
Rt
(min)Rt
(min)area % Rt
(min)area
%
Aspirin
Acetaminophen• Samples containing a single compound are considered PURE samples, while those containing both compounds are considered MIXED (IMPURE) samples.
• Be sure to attach both sample chromatograms to final lab report!
SAFETY CONCERNS
Acetone and ethyl acetate are extremely flammable! Wear safety goggles at all times and use extreme caution when heating!
Hydrochloric acid is corrosive!
WASTE MANAGEMENT The drying agent (MgSO4) and filter
paper should be placed in the container labeled “SOLID WASTE” provided in the hood.
Place all liquid waste in the container labeled “LIQUID WASTE”.
IN LAB QUESTIONS… (The following questions should be answered in laboratory
notebook.)
Draw a complete mechanism for the reaction which occurs between aspirin and 10% NaHCO3 using actual chemical structures and mechanism arrows to indicate electron flow.
+ O OH
O
NaOOH3C
O
O
H
IN LAB QUESTIONS… (The following questions should be answered in laboratory
notebook.)
Draw a complete mechanism for the reaction which occurs between acetaminophen and 10% NaOH using actual chemical structures and mechanism arrows to indicate electron flow.
+ ONa
N
OH
H
CH3
O
H
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