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