CHM557 Experiment 3 Oct 2020-Feb 2021 PDF

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(Online Assessment COVID19)EXPERIMENT 3ESTERIFICATION REACTIONS OF VANILLIN:THE USE OF NMR TO DETERMINE A STRUCTUREDURATION3 hours x 2 weeksOBJECTIVES To synthesize esterification products of vanillin with acetic anhydride under basic and acidic conditions. To determine the melting point of the este...

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UNIVERSITI TEKNOLOGI MARA (UiTM)

ORGANIC CHEMISTRY (CHM556/557) (Online Assessment COVID19)

EXPERIMENT 3 ESTERIFICATION REACTIONS OF VANILLIN: THE USE OF NMR TO DETERMINE A STRUCTURE DURATION 3 hours x 2 weeks

OBJECTIVES 1. 2. 3.

To synthesize esterification products of vanillin with acetic anhydride under basic and acidic conditions. To determine the melting point of the esterification products of vanillin. To characterize the esterification products of vanillin using IR and 1H NMR spectroscopy.

INTRODUCTION In this experiment, you will investigate the reactions between vanillin and acetic anhydride under two conditions, basic and acidic conditions. These reactions will produce different products. You are given two lab sessions to complete this experiment. The first session should be used to conduct the reaction under basic condition. The second session should be used to conduct the reactions under acidic condition. Chemical equation of the esterification of vanillin under basic and acidic conditions is shown below: O C

O H3 C O C

C

O OCH3

NaOH

H

O

O

CH3 C O C CH3

HO OCH3 Vanillin

O H2SO4

Acetic anhydride

O H3 C

C

O C

CH3

C H O C

CH3

O OCH3

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H

O

UNIVERSITI TEKNOLOGI MARA (UiTM)

A.

ORGANIC CHEMISTRY (CHM556/557) (Online Assessment COVID19)

BASIC CONDITION (3 HOURS x 1 SESSION) Watch the video by the following link: https://www.youtube.com/watch?v=aYAVxfclNGI&t=198s

APPARATUS Stainless steel spatula Glass rod PTFE stopper Bulb pipette (if any) Glass pasteur pipette Hirsch funnel Hirsch flask Rubber tubing Rubber bung or rubber filter adapter Bosshead for retort stand Retort stand Retort stand clamp Erlenmeyer flask with a 29/32 socket size (250 mL) Conical flask (100 mL) Beaker Filter paper Measuring cylinder (5 mL, 50 mL) Hot plate Thermometer Glass rod Sample bottle Melting point apparatus Aspirator vacuum pump IR Spectrometer NMR Spectrometer

CHEMICALS Vanillin 10% sodium hydroxide (NaOH) Acetic anhydride 95% ethanol Ice Salt Distilled water

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UNIVERSITI TEKNOLOGI MARA (UiTM)

ORGANIC CHEMISTRY (CHM556/557) (Online Assessment COVID19)

PROCEDURE a.

Preparation of product 1. 2. 3. 4.

5. b.

Dissolve vanillin (1.50 g) in sodium hydroxide (10%, 25 mL) in a 250 mL Erlenmeyer flask. A bright yellow green solution is obtained. Then, add crushed ice (30 g) and acetic anhydride (4.0 mL). On adding acetic anhydride, a cloudy, milky white precipitate forms immediately. Stopper the flask with a clean PTFE stopper and shake it several times over a 20 minutes period. Filter the precipitate using a Hirsch funnel or a small Buchner funnel and wash the solid with ice-cold water (5 mL). Repeat the washing process three times with the ice-cold water (5 mL). Refer to the Figure 3.1 for the setup of a filtration apparatus. Transfer the product (white solid) to the small beaker (50 mL).

Recrystallization of the product 1. 2.

3.

4.

5. 6.

Recrystallize the solid from 95% ethanol. Transfer 95% ethanol (15 mL) in a 100 mL conical flask/beaker and heat the mixture in a hot plate at 60ºC. Stir the mixture and heat it until the entire solid dissolves in the boiling solution. If there is still insoluble solid in your hot mixture, slowly add more solvent (ethanol) and continue heating until completely dissolve. Cool the mixture in room temperature for one minute and continue cooling in an ice bath. If no crystals formed, crystallization can be induced by scratching up and down the inside of the flask with a glass rod. Finally, filter the crystals using a clean Buchner or Hirsch funnel under reduced pressure (see Figure 3.1). At this stage, use a spatula to transfer all the crystals from the flask to the funnel. Wash the crystals with a small amount of cold solvent (95% ethanol). Allow the crystals to dry by sucking air through them. Transfer the dried crystals obtained into a weighed labelled sample bottle. Melting point of the product is below 100ºC. Do not place the product in oven to dry. Determine the melting point of the product (literature value is 77-79ºC). Determine the IR and 1H NMR (in CDCl3) spectra of the product as well as IR spectra for vanillin.

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ORGANIC CHEMISTRY (CHM556/557) (Online Assessment COVID19)

Figure 3.1: Setup of a Filtration Apparatus

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B.

ORGANIC CHEMISTRY (CHM556/557) (Online Assessment COVID19)

ACIDIC CONDITION (3 HOURS x 1 SESSION) Watch the video by the following link: https://www.youtube.com/watch?v=glmLkDQC7hk&t=21s

APPARATUS Erlenmeyer flask with a 29/32 socket size (250 mL) Measuring cylinder (10 mL, 50 mL) Magnetic stir bar Bulb pipette (if any) Glass pasteur pipette or plastic pasteur pipette PTFE stopper (size: 29/32) Beaker Stainless steel spatula Hirsch funnel Hirsch flask Rubber tubing Rubber bung or rubber filter adapter Bosshead for retort stand Retort stand Retort stand clamp Filter paper Glass rod Conical flask (100 mL or 250 mL) Thermometer Sample bottle Hot plate stirrer Melting point apparatus Aspirator vacuum pump IR Spectrometer NMR Spectrometer

CHEMICALS Vanillin 1.0 M sulfuric acid Acetic anhydride 95% ethanol Ice Distilled water

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UNIVERSITI TEKNOLOGI MARA (UiTM)

ORGANIC CHEMISTRY (CHM556/557) (Online Assessment COVID19)

PROCEDURE a.

Preparation of product 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

11. b.

Dissolve vanillin (1.50 g) in acetic anhydride (10 mL) in a 250 mL Erlenmeyer flask. Place a magnetic stir bar in the flask and stir the mixture at room temperature until the solid dissolves. Stopper the flask with PTFE stopper. While continuing to stir the mixture, add drop by drop sulfuric acid (1.0 M, 10 drops) to the reaction mixture. Stopper the flask with PTFE stopper and stir at room temperature for 1 hour. During the period, the solution will turn purple or purple-orange in colour. After 1 hour, cool the flask in an ice-water bath for 4-5 minutes. Add ice-cold water (35 mL) to the mixture in the flask. The mixture will turn to a pale light green in colour. Tightly stopper the flask with a clean PTFE stopper and while holding your thumb on the stopper, shake the flask vigorously-almost hard as you can shake! Continue to cool and shake the flask to induce crystallization. Crystallization has occurred when you can see small solid clumps separating from the cloudy liquid and settling to the bottom of the flask. Filter the solid or crystal using a Hirsch funnel or a small Buchner funnel and wash the solid with ice-cold water (5 mL). Repeat the washing process three times with the ice-cold water (5 mL). Refer to the Figure 3.1 for the setup of a filtration apparatus. Transfer the product (white solid) to the small beaker (50 mL).

Recrystallization of the product 1. 2.

3.

4.

5. 6.

Recrystallize the solid from 95% ethanol. Transfer 95% ethanol (15 mL) in a 100 mL conical flask/beaker and heat the mixture in a hot plate at 60ºC. Stir the mixture and heat it until the entire solid dissolves in the boiling solution. If there is still insoluble solid in your hot mixture, slowly add more solvent (ethanol) and continue heating until completely dissolve. Cool the mixture in room temperature for one minute and continue cooling in an ice bath containing a little bit of salt. If no crystals formed, crystallization can be induced by scratching up and down the inside of the flask with a glass rod. Finally, filter the crystals using a clean Buchner or Hirsch funnel under reduced pressure (see Figure 3.1). At this stage, use a spatula to transfer all the crystals from the flask to the funnel. Wash the crystals with a small amount of cold solvent (95% ethanol). Allow the crystals to dry by sucking air through them. Transfer the dried crystals obtained into a weighed labelled sample bottle. Melting point of the product is below 100ºC. Do not place the product in oven to dry. Determine the melting point of the product (literature value is 90-91ºC). Determine the IR and 1H NMR (in CDCl3) spectra of the product as well as IR spectra for vanillin.

RESULTS AND OBSERVATIONS OCT-FEB 2021_COVID19

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A.

ORGANIC CHEMISTRY (CHM556/557) (Online Assessment COVID19)

BASIC CONDITION Results: a.

Weight of product

:

b.

Melting point of the product

: ______ ºC

c.

Appearance of the product

: _______________

e.

IR data (in Table): i. ii.

Vanillin Product Wavenumber (cm-1)

f.

1

1.1123 g

Type of bond (group)

H NMR data of the product (in Table): Chemical shift, δ (ppm)

Multiplicity

Number of hydrogen

Type of proton

Observations: Write the observations such as colour changes, colour of the precipitate etc during the period of experiment. Steps

Observations

Calculations/Task: a. b. c. d.

Calculation of theoretical yield of product. Percentage yield of product. Discuss the IR and NMR spectrums given with regard to the structures (Table e and f). Name the products and draw their reaction mechanisms.

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B.

ORGANIC CHEMISTRY (CHM556/557) (Online Assessment COVID19)

ACIDIC CONDITION Results: a.

Weight of product

: 2.3979 g

b.

Melting point of the product

: ______ ºC

c.

Appearance of the product

: _______________

e.

IR data (in Table): i. ii.

Vanillin Product Wavenumber (cm-1)

f.

1

Type of bond (group)

H NMR data of the product (in Table): Chemical shift, δ (ppm)

Multiplicity

Number of hydrogen

Type of proton

Observations: Write the observations such as colour changes, colour of the precipitate etc during the period of experiment. Steps

Observations

Calculations/Task: a. b. c. d.

Calculation of theoretical yield of product. Percentage yield of product. Discuss the IR and NMR spectrums given with regard to the structures (Table e and f). Name the products and draw their reaction mechanisms.

OCT-FEB 2021_COVID19

UNIVERSITI TEKNOLOGI MARA (UiTM)

ORGANIC CHEMISTRY (CHM556/557) (Online Assessment COVID19)

QUESTIONS 1.

Under different reaction media, vanillin undergoes esterification with acetyl chloride yielding two different products.

O H

O Basic or acidic medium Cl

HO

?

OCH3 Vanillin

a. b. c.

2.

Based on the IR spectrum of vanillin, at what range should you observe the absorption signal of the hydroxyl group? Based on its 1H NMR spectrum, what is the expected chemical shift value for the methoxy group (OCH3)? What is its multiplicity? Draw the structures of the major products for the esterification of vanillin with acetyl chloride in: i. 10% NaOH solution ii. 1.0 M H2SO4 solution

Write the mechanism for the reaction between vanillin and acetyl chloride in 10% NaOH solution.

REFERENCE Pavia, Lampman, Kriz and Engel, Introduction to Organic Laboratory Techniques 3rd Edition (2011). page 863-865.

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YOUR WRITTEN REPORT MUST HAVE:

Front Page: Name Student No Group Experiment Title Date of Experiment

: : : : :

Objective: (1M) Introduction: (2M) Summarize the experiment briefly, add mechanism here Procedure in flowchart: (2M) Calculation: (5M) Discussion: (3M) Summarize the IR spectrum briefly. Conclusion:(1M) Questions: (6M) References:

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Appendix 1: IR spectrum in Acid Condition

Appendix 2: IR spectrum in Basic Condition

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Appendix 3: NMR Spectrum for Acid Condition

Appendix 4: NMR Spectrum for Basic Condition

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