EXPERIMENT 1 - UniMAP Portalportal.unimap.edu.my/portal/page/portal30/Lecturer Notes... · Web...

Organic Chemistry (ERT 102) Laboratory Module

EXPERIMENT 1Chlorophyll Extraction, Column and Thin Layer

Chromatography1. OBJECTIVE :

1.1 To extract pigments from spinach leaves

1.2 To separate the pigments by column and thin layer chromatography

2. INTRODUCTION

Green leaves contain a variety of organic compounds. The compounds of long-chain, conjugated absorb visible light and reflect the leaf green color. The leaf green color consists of common pigments such as carotenes (α and β), lycopenes, chlorophyll (a and b), cryptoxanthins (α and β), pheophytins (a and b) and xanthophylls. The lycopenes are the non-cyclic analogues to the carotene; the cryptoxanthins and xanthophylls are the derivatives of carotenes. The chlorophyll can be converted to the pheophytin in certain conditions. The pheophytins are the same as the cholorophyll, but without the central magnesium (Mg) atom. The cholorophyll structure is as shown in Figure 1.

Figure 1: Chemical structure of cholorophyll

The chlorophyll is a large molecule, thus it has very low vapor pressure. Because of this reason, purification methods, which depend upon volatility cannot be used to separate it. Two effective methods to separate the chlorophyll from the pigments are column and thin layer chromatography (TLC).

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3. APPARATUS/CHEMICALS/MATERIAL:

3.1 Conical flasks

3.2 Beakers

3.3 Separatory funnel

3.4 Acetone

3.5 Hexane

3.6 Sodium chloride

3.7 Anhydrous sodium sulfate

4. PROCEDURES

4.1 Extraction of pigments

4.1.1 Cut 10-15 g of frozen spinach leaves into small pieces and place them in a 500ml beaker.

4.1.2 Add 25ml of acetone to the spinach and mix with a glass rod or spatula. Let the mixture stand for at least 5 minutes in a fume hood.

4.1.3 Carefully decant the acetone extract into a 125ml separatory funnel. DO NOT transfer the spinach leaves. Then use a 250 ml Erlenmeyer flask to press the spinach leaves.

4.1.4 Add another 25ml acetone to the spinach leaves and mix as in step 4.1.2. Repeat step 4.1.3. Discard the spinach leaves into a waste container.

4.1.5 Add 25ml of hexane to the separatory funnel and mix with venting. Record your observations. Refer to Figure 1 below for stand and venting of the separatory funnel.

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Figure 1: The separatory funnel in the ring stand (above), and steps for venting the funnel (below).

4.1.6 Add 25ml of saturated sodium chloride to the separatory funnel and mix. Allow the layers to separate. Collect the upper layer (organic) in a beaker and transfer the bottom layer (aqueous) to another beaker. NOTE: Label the beakers.

4.1.7 Wash the aqueous layer with 25ml of hexane in a separatory funnel. Combine the organic layer.

4.1.8 Extract the combined organic layers with 25ml of saturated sodium chloride. Let the layers to separate and discard the bottom layer (aqueous).

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Organic Chemistry (ERT 102) Laboratory Module4.1.9 Dry the organic layer by passing it through a funnel containing 5±0.1g of anhydrous sodium sulfate (use cotton and glass wool plug in the funnel to dry the organic mixture).

4.1.10 Keep the dried organic mixture in a water bath for about 10-15 minutes (68 oC) to concentrate the extract. The concentrated extract will be used for column and thin layer chromatography analysis.

4.2 Column Chromatography

(Steps 4.2.1-4 are prepared by the lab technician)

4.2.1 The column used should have a 2cm O.D and be approximately 32cm in length. The column must be clean and dry before using.

4.2.2 Place a small piece of cotton (pea size) into the column, (use a glass rod or airline to get the cotton to the bottom of the column). Clamp the column to a ring stand using a micro clamp. Add 0.4g of sand to the column.

4.2.3 Add 10g of alumina to the column and gently tap the column to settle the alumina. NOTE: a small disposable pipet with the ends cut off can be used as a funnel. Make sure each layer in the column is level before adding the next.

4.2.4 Add the dried sample to the column.

4.2.5 Finish packing the column by adding 0.6g of sand to the column. A sample of how the column should look is illustrated in Figure 2.

Figure 2: Column set-up

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Organic Chemistry (ERT 102) Laboratory ModuleRunning the column

4.2.6 Slowly add mobile phase of 95: 5 ethyl acetate: ethanol to the column (≈ 8ml).

4.2.7 The first fraction to elute from the column is yellow. The second fraction is yellow-green (eluent between distintly color band). The last fraction is green. Collect the last fraction. Save the fraction for TLC analysis.

4.3 Thin Layer Chromatography

4.3.1 Prepare aluminium plate.

4.3.2 Using a sharp pencil, draw a straight line horizontally across the plate and about 10 mm height from below the plate. The plate is as shown in Figure 3b.

4.3.3 Make 2 spots of equivalent distance from each other on the straight line. The plate will be spotted with 2 samples (i.e. 1. The initial pigments extract; 2. Green fraction collected from the column chromatography)

4.3.4 Dip a capillary tube into the pigments extract.

4.3.5 On the aluminium plate, make a contact between the dipped capillary tube and the exact first spot of each plate. The quantity of liquid inside the capillary tube should be minimum.

4.3.6 Leave the spots to dry.

4.3.7 Repeat the dropwise addition for the second and third time.

4.3.8 Ensure that each drop size is minimized.

4.3.9 Using a new capillary tube, drop the green fraction from column chromatography solution onto the second mark on the aluminium plate three times.

4.3.10 Repeat the procedures.

4.3.11 Prepare a solution of 70:30 ml Hexane: Acetone and place it in a TLC development chamber (or beaker) of about 5mm deep. Set-up the chamber as shown in Figure 3a.

4.3.12 Put one plate, with the spots below into the chamber containing the solvent solution.

4.3.13 Put the lid on the beaker and allow the solvent travels until 0.5 cm from the upper end of the plate.

4.3.14 Remove the plate and using a pencil, mark the front solvent.

4.3.15 Leave the plate to dry.

4.3.16 Calculate the Rf value for each spots of the plate.

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Figure 3a: TLC chamber Figure 3b: TLC plate

4 RESULTS

Calculate the Rf values for each spots separated on the TLC plate

5 DISCUSSION & EVALUTION /EXERCISES:

5.1 During extraction of pigments when the acetone pigment mixture was mixed with hexane and allowed to stand what happened?

5.2 If pure acetone and hexane are mixed (Hint: Mix them in a separatory funnel) what should happen and why did not this occur in this experiment?

5.3 What does Rf stand for?

5.4 Why can a mixture of organic components be separated by thin layer chromatography?

5.5 The versatility of column chromatography results from the many factors that can be adjusted. Name three of them?

6 CONCLUSIONBased on the experimental procedure done and the results taken, draw some conclusions to these experiments.

Safety precautions:

1. Make sure that you do not accidentally drop any samples solution on the plate.

2. Wear gloves when handling the finished plates.

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EXPERIMENT 2Fractional Distillation of Diethyl Ether and 1,2-Dimethoxy

Ethane

1. OBJECTIVE:

1.1 To fractionally distill a mixture of ethyl ether and 1,2-dimethoxy-ethane

1.2 To fractionally distill the mixture using three types of column packing material

1.3 To collect the fractions and plot a distillation curve

1.4 To compare the effect of the packing materials on the distillate

INTRODUCTION

Fractional distillation is separation of a mixture of two or more liquids that present in noticeable amounts into several fractions. Basically, the fractional distillation is a systematic way to redistilate the distillates (fractions of increasing purity). Figure 1 and 2 illustrate the distillation curves on how the two liquids separate. Figure 1 below shows an ideal distillation curve.

Figure 1: Ideal separation distillation curve

3. APPARATUS/CHEMICALS/MATERIALS:

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Organic Chemistry (ERT 102) Laboratory Module3.1 ethyl ether

3.2 1,2-dimethoxy-ethane

3.3 Packing materials:i. Copper ribbonii. 6mm glass beadsiii. Raschig rings

3.4 Fractional distillation apparatus set

3.5 10 ml measuring cylinder

3.6 5 ml screw cap vials

3.7 Boiling stones

4. PROCEDURE:

4.1 Set-up the fractional distillation apparatus (Figure 3) using one of the packing materials listed above. The teaching engineer/ technician will indicate which packing material to use.

Figure 3: Fractional distillation set-up

4.2 Place 60ml of 1:1 Ethyl ether: 1,2-dimethoxy ethane into the distilling flask (round bottom flask). Add 2-3 boling stones to the flask.

4.3 Distill the mixture by heating the heating mantle at rate of distillate production

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Organic Chemistry (ERT 102) Laboratory Moduleof 1-2 drop per second

4.4 Record the temperature for every 1-2ml of distillate collected. If the temperature begins to drop, increase the the power of the heating mantle.

4.5 Collect ten 5ml fractions using a 10ml measuring cylinder. Keep the fractions in screw cap vials.

4.6 After finish collected the tenth fraction, remove the heating mantle and let the apparatus cool.

4.7 Send your raw data of temperature and distillate volume to the teaching engineer.

5. RESULTS

Plot the distillation curve of temperature versus distillate volume for each type of packing material.

6. DISCUSSION & EVALUTION /EXERCISES

6.1 At what volume of distillate collected, during fractional distillation, would a rapid increase in temperature be expected for 1000ml of a 1;1 mixture of and ideal solution?

6.2 Which packing material provided the most ideal separation?

6.3 How might the separation of ethyl ether and 1,2-dimethox ethane be improved using one of the packing materials used in this experiment

7. CONCLUSION

EXPERIMENT 3Separation of Benzoic Acid and Biphenyl

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1. OBJECTIVE

1.1 To separate a mixture of benzoic acid and biphenyl by extraction

1.2 To recover the separated compounds

1.3 To calculate the recovery percentage

2. INTRODUCTION

Organic solution of benzoic acid and biphenyl can be separated by liquid-liquid extraction. Benzoic acid is an organic acid with carboxylic acid functional group (-COOH). Biphenyl is a typical organic hydrocarbon and is neither acidic nor basic. The more polar benzoic acid molecules will be extracted to an aqueous basic solvent, while the biphenyl will be moved into organic layer.

The benzoic acid is recovered by acidifying the aqueous solution, which causes the benzoic acid to precipitate, whereupon it is isolated by filtration. The biphenyl is isolated by drying the aqueous solution to remove dissolved water, and finally distillation of the solvent – the biphenyl will remain as a non-volatile residue. The whole operation is accomplished simply in a short period of time using these principles of extraction. The three components are isolated in nearly pure form; minor contaminants could be removed, if desired, by recrystallization (Experiment 4).

3. APPARATUS/CHEMICALS/MATERIALS

3.1 Benzoic acid3.2 Biphenyl3.3 Separatory funnel3.4 Ethyl ether3.5 Beaker3.6 Erlenmeyer flask3.7 Anhydrous sodium sulfate3.8 Round bottom flask3.9 Rotary evaporator3.10 Hydrocloric acid

4. PROCEDURE:

Extraction of benzoic acid and biphenyl mixture

4.1 Place 2.5±0.01g of benzoic acid and 2.5±g biphenyl into a 125ml separatory funnel. Record the exact weight of the compounds to the nearest 0.01g.

4.2 Dissolve the benzoic acid and biphenyl mixture in 50ml ethyl ether.

4.3 Extract the mixture with five 25ml portions of 5% sodium bicarbonate

4.4 Combine the aqueous layer (sodium bicarbonate extractions) in a 400ml beaker.

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Organic Chemistry (ERT 102) Laboratory Module4.5 Place the organic (ether) layer in a 125ml Erlenmeyer flask

Biphenyl recovery

4.6 Add 1-2g of anhydrous sodium sulfate to the ether biphenyl mixture. Swirl the flask to thoroughly mix the contents.

4.7 Let the sodium sulfate settle and the decant the solution mixture into a pre-weighed 100ml round bottom flask

4.8 Remove the ether in the solution using a rotary evaporator. Weight the flask and record the weight of biphenyl recovery. Calculate the percent recovery.

4.9 Keep the recovered biphenyl for a next experiment (Experiment 4).

Benzoic acid recovery

4.10 Cool the beaker containing aqueous extracts in an ice bath for at least five minutes.

4.11 Add 6M HCL in 1-2ml portions until no more precipitate forms in the aqueous extracts.

4.12 Collect the crystal by vacuum filteration and dry the crystal in the funnel for at least ten minutes.

4.13 Determine the weight of benzoic acid recovered and calculate the recovery percentage.

4.14 Keep the recovered benzoic acid for the next experiment (Experiment 4).

4. RESULTS

i. Biphenyl recovery

Mass of flask:

Mass of flask with recovered biphenyl:

Mass of recovered biphenyl:

Percentage yield of recovered biphenyl:

ii. Benzoic acid recovery

Mass of flask:

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Organic Chemistry (ERT 102) Laboratory ModuleMass of flask with recovered benzoic acid: Mass of recovered benzoic acid

Percentage yield of recovered benzoic acid:

Calculation of % of recovery:

%Recov ery=mass of recovered substance ( g )mass of crude substance ( g )

×100

5. DISCUSSION & EVALUTION /EXERCISES

5.1 Define extraction?

5.2 How can the organic layer be determined during extraction?

5.3 What are four common signs that indicate an organic solution is dry?

5.4 Write the equation for the reaction of sodium bicarbonate with benzoic acid.

5.5 Why is the beaker containing the bicarbonate extracts cooled before adding HCl?

6. CONCLUSION

EXPERIMENT 4Crystallization of Benzoic Acid and Biphenyl

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1. OBJECTIVES

1.1 To crystallize the recovered benzoic acid using water

1.2 To crystallize the recovered biphenyl using appropriate solvent

2. INTRODUCTION

Crystallization is a method to purify a solid. The process requires a suitable solvent. A suitable solvent is one which readily dissolves the solid (solute) when the solvent is hot but not when it is cold. The best solvent exhibits a large difference in solubility over a reasonable range of temperatures. (e.g, Water can be a crystallization solvent between 0-100 oC; hydrocarbon solvents such as hexanes or petroleum ether have a different temperature range since they can be cooled below 0 oC but boil below 100 oC). During crystallization, a crude solid is boiled with appropriate solvent until the solid is completely dissolved. If the saturated hot solution is allowed to cool, solute is no longer soluble in the solvent and forms crystals of pure compound. Impurities are excluded from the growing crystals and the pure solid crystals can be separated from the dissolved impurities by filtration.

3. PROCEDURES

Crystallization of Benzoic acid

3.1 Determine the melting of the crude benzoic acid (sample from Experiment 3)

3.2 Weight 2 ± 0.01g (record the exact weight) of benzoic acid and transfer it into a 250ml Erlenmayer flask.

3.3 Add 40ml of distilled water to the flask.

3.4 Heat the mixture on a hot plate up to the boiling point while stirring the mixture. Boil until the benzoic acid completely dissolved.

3.5 Remove the flask from the hot plate. If undissolved benzoic acid particles still appear in the mixture, add an additional small amount of distilled water (several drops at a time from a Pasteur pipette) and continue boiling the solution.(NOTE: Adding too much volume of distilled water will cause the solution not be saturated thus reducing the yield of purified benzoic acid).

3.6 Determine the melting point of the crystallized benzoic acid.

3.7 Calculate the percent recovery of the pure benzoic acid.

Crystallization of biphenyl

3.8 Determine the melting point of the crude biphenyl (sample from Experiment 3).

3.9 Set-up a reflux apparatus using 50ml round bottom flask as shown in Figure 1.

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3.10 Place 2 ± 0.01g (record the exact weight) of crude biphenyl in the flask and attach the condenser.

3.11 Start circulating the water through the condenser.

3.12 Add enough solvent to just cover the biphenyl in the flask through the top of the condenser using a disposable pipette.

3.13 Heat the flask using a heating mantle until all the biphenyl dissolves or the solvent begins to boil.

3.14 If the solvent begins to boil before the biphenyl completely dissolved adds more solvent dropwise until all the biphenyl completely dissolved (continue heating). If the solvent begins to boil too rapidly remove the heating mantle and let the flask cool.

3.15 Once experiment finished, let it cool for several minutes before turning off the cooling water. Then, remove the condenser.

3.16 If the biphenyl crystal does not appear after the cooling process, induce the crystallization process. To induce the process, scrape the sides of the flask above the level of the solution. This may dislodge some undetectable, small crystals that will drop into the solution and “seed” the solution. A seed solution may help to induce crystallization.

3.17 Collect the solid using a vacuum filteration. Hands dry the solid using clean paper towel, let them dry completely.

3.18 Weight the solid and calculate the percentage of biphenyl recovery through the crystallization process.

3.19 Determine the melting point of your crystallized biphenyl.

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Figure 1: Apparatus set-up for reflux

4. RESULTS

SubstanceBenzoic acid Biphenyl

Mass of impure substance (From Experiment 3)Mass of crystallized substance + weighing paperMass of weighing paperMass of crystallized substanceCalculation percentage of substance recoveryMelting point of crystallized substance

Calculation of % of recovery:

%Recov ery= mass of crystallised substance (g )mass of substance before crystallisation ( g )

×100

5. DISCUSSION & EVALUTION /EXERCISES:

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5.1 When a solid compound is contaminated what happens to its melting point?

5.2 What is a main characteristic of a good solvent used in crystallization?

5.3 Why may be the use of a reflux apparatus be preferred for performing a crystallization?

5.4 After crystallization, why are the crystals washed with cold solvent?

6. CONCLUSION

EXPERIMENT 5

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O

R - C -O -R'

O

R - C - OH

R' O H

O

R - C -O -R'+ H3O++

H+


Synthesis, Purification and Quantification of Ester

1. OBJECTIVE

1.1 To synthesize ester from carboxylic acid and alcohol reaction

1.2 To purify ester through distillation

1.3 To quantify ester using Gas Chromatography

2. INTRODUCTION

Esters are naturally abundant and readily synthesized, but all have the same following structure.

Every day fragrances, such as the “rich smell’ of fresh ground coffee, are a combination of esters (>200 identifiable esters found so far in coffee!). However, some esters are readily recognized by their very characteristic flavor or odor.

In the Table 1 below, several examples of esterification products are given.

Table 1: Combinations of carboxylic acids and alcohols resulting in estersEster Structure Fragrance Carboxylic

acidAlcohol

Iso-butyl formate

HCO2CH2CH(CH3)2 Raspberry essence

Formic acid Iso-butanol

Propyhl acetate

CH3CO2CH2CH2CH3 Pear essence

Acetic acid 1-propanol

Octyl acetate

CH3CO2CH2(CH2)6CH3 Orange essence

Acetic acid octanol

Ethyl butyrate

CH3CH2CH2CO2CH2CH3 Pineapple essence

Butyric acid ethanol

Methyl butyrate

CH3CH2CH2CO2CH3 “Apple like” essence

Butyric acid methanol

In esterification reaction, esters can be prepared by reversible, acid-catalyzed, combination of a carboxylic acid with an alcohol. Because it is reversible, the reaction must be shifted to the product side by using excess reagent, or removing one of the products. This reaction is also limited by any steric hindrance in the carboxylic acid or the alcohol. The general equation for an esterification is shown below.

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O

R - C - OH

R' O H

O

R - C -O -R'+ H3O++

H+

Organic Chemistry (ERT 102) Laboratory Module3. EQUIPMENT / APPARATUS

3.1 Distillation apparatus

3.2 Isoamyl Alcohol

3.3 Acetic acid

3.4 parafilm

3.5 distilled water

3.6 methylene chloride

3.7 Erlenmeyer flask

3.8 Stopper

3.9 Rotary evaporator

3.6 10% Na2CO3

3.7 Sodium sulphate Na2SO4

4. PROCEDURES

4.1 Part A – Synthesis of the ester

4.1.1 Mix 100ml of 0.05 moles of isoamyl alcohol and 250ml of 0.125 moles of acetic acid in an Erlenmeyer flask

4.1.2 Add 1ml of concentrated sulfuric acid and gently swirl the flask to mix the con-tents.

4.1.3 Stopper the flask and wrap with parafilm.

4.1.4 Let the reaction occurs for 40 minutes.

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Organic Chemistry (ERT 102) Laboratory Module4.2 Part B – Purification of the ester

4.2.1 Pour contents of the reaction flask into the separatory funnel.

4.2.2 Rinse the flask with both 12 mL of methylene chloride and 10 mL of water and add these rinses to the separatory funnel also.

4.2.3 Shake, then separate the aqueous and organic layer: if two layers are not visi-ble, add 10 mL of water to the separatory funnel. Differentiate the aqueous and or-ganic layer.

4.2.4 Re-extract the aqueous layer with another 12 mL of methylene chloride. Com-bine the organic layers and wash them twice with 8 mL of 10% Na2CO3.

4.2.5 Dry the organic layer over anhydrous sodium sulfate.

4.2.6 Swirl the mixture from time to time over 10 minute-period. Then allow the sodium sulfate to settle and transfer the organic layer into a clean and dry container.

4.2.7 Place your sample in a 100 mL round bottom flask. Your teaching engineer will show you how to use the rotary evaporator.

4.2.8 After removal of the methylene chloride, place your sample in a 50 mL round bottom flask. Record the boiling point of the ester. Collect it in a clean container.

4.2.9 Run a GC to determine its purity with a help of your teaching engineer.

*Safety precautions

*H2SO4 is very corrosive; if it comes in contact with your skin, flush immediately with large amounts of water. Although

*Less corrosive than H2SO4, acetic acid is also corrosive and should be rinsed imme-diately off the skin.

*Chemical like methylene chloride is mild irritants and/or poisonous if ingested in large amounts and skin contact and inhalation of vapors should be avoided.

*Several reagents used are flammable; do not use flames in this lab. Wear gloves and protective clothing.

*Isoamyl alcohol is an irritant. Avoid breathing vapors.

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Organic Chemistry (ERT 102) Laboratory Module5. RESULTS

5.1 The boiling point of ester:

6. QUESTIONS

6.1 Write the chemical reaction between the reactants in the experiment. Find the equilibrium constant.

6.2 What is the name of the ester produced? Find the application.

6.3 Why did you wash your product with methylene chloride? What was the purpose of washing with water?

6.4 Explain the function of the acid catalyst in a Fisher Esterification reaction.

6.5 Determine the yield of the ester.

7. DISCUSSIONDiscuss the results you gained from the gas chromatography.

8. CONCLUSIONBased on data and discussion, make your overall conclusion by referring to the experimental objective.

EXPERIMENT 6Synthesis of Polyamide- Nylon 6, 10

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1. OBJECTIVE

1.1 To synthesize nylon 6, 10 from hexamethylenediamine

1.2 To calculate weight of the nylon synthesized

2. INTRODUCTION

A linear polyamide is formed through a condensation reaction between a dicarboxylic acid and a diamine. Nylon 6, 6 is the commercial nylon which produces from adipic acid and hexamethylenediamine. The polyamide, nylon 6, 6 shows that its monomer of has six carbons. There is another way to produce nylon 6,6, it can be made by us-ing the acid chloride of adipic acid (adipoyl chloride)

This experiment is conducted to synthesize a polyamide, nylon 6, 10. In order to pro-duce nylon 6,10, the amine molecule must have a –NH2 group at each end, and the acid chloride must have a –COCl group at each end. The diamine and the diacid chloride bond together, end-on-end, to form very long chains. Nylon 6, 10 is synthe-sized from the acid chloride of sebacic acid (sebacoyl chloride) and hexamethylene-diamine. The sebacoyl chloride dissolved in cyclohexane, which carefully added to hexamethylenediamine dissolved in water. As a result, two layers are formed. The polymer then be drawn out to develop a continous strand of nylon. Figure 1 below shows the reaction of nylon 6, 10 formation.

Figure 1: Formation of nylon 6, 10 from hexamethylene diamine and sebacoyl chloride

3. EQUIPMENT / APPARATUS

3.1 Sebacoyl chloride

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Organic Chemistry (ERT 102) Laboratory Module3.2 Hexamethylene diamine

3.3 Cyclohexane

3.4 Sodium hydroxide

3.5 Aluminium or copper wire

3.6 Beakers

4. PROCEDURES

4.1 Pour 10ml of 5% aqueous hexamethylenediamine into a 50ml beaker

4.2 Add 10 drops of 20% sodium hydroxide

4.3 Carefully add 10ml of 5% sebacoyl chloride in cyclohexane to the beaker.

4.4 Draw out the nylon that is formed at the interface of the two solutions slowly, using alluminium of cooper ware as a hook.

4.5 P,ace the nylon strand on a piece of paper towel and press it to dry (use the bench top hood).

4.6 Mix the contents of the beaker vigorously using the wire hook. Decant the liquid into a proper waste container. Wash the remaining nylon in the beaker with water and let it dry.

4.7 Determine the weight of the synthesized nylon 6, 10.

5. RESULTS

5.1 Calculate the yield of the nylon 6, 10 in this experiment. (Hint: To calculate the yield, cancel out the n’s from the formation equation (Figure 1)).

6. DISCUSSIONDiscuss the results you gained from the gas chromatography.

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Organic Chemistry (ERT 102) Laboratory Module7. CONCLUSIONBased on data and discussion, make your overall conclusion by referring to the experimental objective.

EXPERIMENT 7Synthesis of Acetaminophen (Paracetamol)

1. OBJECTIVES

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1.1 To synthesize paracetamol from p-aminophenol and acetic anhydride

1.2 To calculate the yield of the synthesized paracetamol

1.3 To determine the boiling point of the paracetamol

2. INTRODUCTION

Paracetamol is a very widely used medicine. It is a mild painkiller and reduces the temperature of patients with fever. These actions are known respectively as analgesic and antipyretic.

Synthesis of paracetamol involves three steps from phenol. The first step is nitration of phenol to form 4-nitrophenol and 2- nitrophenol. Then, the second step is reduction of nitro group to amine. The last step is formation of amide, which produce paracetamol. Starting material for any synthesis should be such that it is easily available. Phenol though easily available, was not used as a starting material because of the difficulty of separation of the isomers after nitration and the subsequent reduction. So 4-aminophenol was used as the starting point. Thus, in this experiment, the synthesis of paracetamol starts from p-amoniphenol. The chemical reaction of the synthesis is as shown below:

3. GLASSWARES/CHEMICALS

3.1 4-aminophenol

3.2 Acetic anhydride

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Organic Chemistry (ERT 102) Laboratory Module3.3 Pure paracetamol

3.4 Heating mantle

3.5 Round bottom flask 50 ml

3.6 Buchner funnel

3.7 Elenmeyer flask

3.8 Beaker 100ml

3.9 Glass rod

4.0 Petri dish

4. PROCEDURES

4.1 Place 5.5g of p-aminophenol in a 50ml round bottom flask.

4.2 Add 15ml of distilled water to the p-aminophenol in the round bottom flask.

4.3 Drop 6ml of acetic anhydride carefully in the mixture of p-aminophenol and distilled water.

4.4 Set up the reflux apparatus

4.5 Reflux the mixture for 20 minutes.

4.6 After all the substrate dissolved, let the solution cool down.

4.7 Filter the crystal that appear in the flask on the Butcher funnel

4.8 Wash the crystal with cold water until the filtrate change to pH 7

4.9 Add 20ml distilled water to the synthesized crude paracetamol and reflux again to recrystallize it. (Detail recrystallization methods can be referred to the previous experiment).

4.10 Pour the hot solution into small beaker and cool down in ice water bath.

4.11 Filter the product and hand dry using paper towel

4.12 Determine the mass of the paracetamol.

4.13 Calculate the yield and determine the melting point of the synthesized paracetamol.

5. RESULTS

6. DISSCUSSION/EXERCISES

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7. CONCLUSION

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