CHM556 exp3 - Lab report esterification reactions of vanillin PDF

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Lab report esterification reactions of vanillin...

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TITLE: Esterification reactions of vanillin: The use of NMR to determine a structure.

OBJECTIVE: •

To investigate the reactions between vanillin and acetic anhydride under basic and acidic conditions.

•

To measure the melting point of vanillyl acetate in different conditions of reaction.

•

To calculate the percentage yield of vanillin acetate for both conditions.

INTRODUCTION: Vanillin is a phenolic aldehyde, which is an organic compound with the molecular formula C8H8O3. Its functional groups include aldehyde, hydroxyl and ether. It is synthetic and may be produced using petrochemicals and by-products from the paper industry. Vanillyl acetate is a flavouring material and its molecular formula is C10H10O4. Acetic anhydride is the simplest isolable anhydride of a carboxylic acid. It is a colourless liquid that smells strongly of acetic acid, which is formed by its reaction with moisture in the air. Acetic anhydride is an irritant and combustible liquid. Because of its reactivity toward water, alcohol foam or carbon dioxide are preferred for fire suppression. The vapour of acetic anhydride is harmful. Chemical reaction of two reactants to form an ester as the reaction product is called as esterification. In this experiment, we used sodium hydroxide as base solution and sulphuric acid as acid solution. The product of reaction between vanillin and acetic anhydride under acidic condition and basic condition will give different structure in FTIR and NMR spectrum.

PROCEDURE: Preparation of 4-Acetoxy-3-Methoxybenzaldehyde (Vanillyl Acetate) 1.50 g of vanillin had been dissolved in 25 mL of 10% sodium hydroxide in a 250-mL Erlenmeyer flask. 30 g of crushed ice and 4.0 mL of acetic anhydride had been added. The flask had been stoppered with a clean rubber stopper and the flask had been shaken several

times over a 20-minute period. A cloudy, milky white precipitate had been formed immediately when adding acetic anhydride. The precipitate had been filtered using a small Buchner funnel and the solid had been washed with three 5-mL portions of ice-cold water. The solid had been recrystallized from 95% ethyl alcohol. The mixture had been heated in a hot-water bath at about 60ºC to avoid the solid melted. The solid had been weighed after the crystal had been dried and the percentage yield had been calculated. The melting point had been obtained. The infrared spectrum of the product had been determined using the dry-film method. The proton-NMR spectrum of the product had been determined in CDCl3 solution. The structure of the product had been confirmed that is consistent with the predicted result using the spectral data. Esterification of Vanillin in the Presence of Acid 1.50 g of vanillin had been dissolved in 10 mL of acetic anhydride in a 125-mL Erlenmeyer flask. A magnetic stir bar had been placed in the flask, and the mixture had been stirred at room temperature until the solid dissolves. 10 drops of 1.0 M sulfuric acid had been added to the reaction mixture while continuing to stir the mixture. The flask had been stoppered and had been stirred at room temperature for 1 hour. The solution had been turned into purple or purple-orange in colour during this period. The flask had been cooled in an ice-water bath for 4-5 minutes at the end of the reaction period. 35 mL of ice-cold water had been added to the mixture in the flask. The flask had been stoppered tightly with a clean rubber stopper and the flask had been shaken vigorously while holding thumb on the stopper. The flask had been cooled continuously and had been shaken to induce crystallization. Crystallization had been occurred when small solid clumps separated from the cloudy liquid and settled to the bottom of the flask. The product had been filtered on a small Buchner funnel and the solid had been washed with three 5-mL portions of ice-cold water. The crude product had been recrystallized from hot 95% ethanol. The crystals had been allowed to dry. The dried crystals had been weighed, the percentage yield had been calculated and the melting point had been determined. The infrared spectrum of the product had been determined using the dry-film method. The proton NMR spectrum of the product had been determined in CDCl3 solution.

RESULT: CONDITION

BASIC

ACIDIC

Mass of vanillin

1.5028 g

1.5166 g

Mass of beaker

65.9565 g

65.9565 g

Mass of beaker + vanillyl acetate

67.4544 g

70.3100 g

Mass of vanillyl acetate

1.4979 g

4.3535 g

Melting point

72 ºC – 75 ºC

78 ºC – 84 ºC

Percentage yield

78.808%

224.871%

CALCULATION: C8H8O3 + (CH3CO)2O → C10H10O4 + CH3COOH In basic condition Mass of vanillin = 1.5028 g Moles of vanillin: Mole = mass/RMM

RMM of vanillin = 152.15 g/mol

Mole = 1.5028/152.15 = 0.00988 mol Moles of vanillyl acetate: 1 mole of vanillin : 1 mole of vanillyl acetate So, mole of cyclohexanol = 0.00988 mol Theoretical mass of vanillyl acetate: Mass = mole x RMM Mass = 0.00988 x 194.18 = 1.9185 g Percentage yield of vanillyl acetate: % yield = actual / theoretical x 100% = 1.4979 / 1.9185 x 100% = 78.808%

RMM of vanillyl acetate = 194.18 g/mol

In acidic condition Mass of vanillin = 1.5166 g Moles of vanillin: Mole = mass/RMM

RMM of vanillin = 152.15 g/mol

Mole = 1.5166/152.15 = 0.00997 mol Moles of vanillyl acetate: 1 mole of vanillin : 1 mole of vanillyl acetate So, mole of cyclohexanol = 0.00997 mol Theoretical mass of vanillyl acetate: Mass = mole x RMM

RMM of vanillyl acetate = 194.18 g/mol

Mass = 0.00997 x 194.18 = 1.9360 g Percentage yield of vanillyl acetate: % yield = actual / theoretical x 100% = 4.3535 / 1.9360 x 100% = 224.871%

DISCUSSION: A phenolic aldehyde, which is an organic compound with the molecular formula C8H8O3 was called as vanillin. In this experiment, the purpose is to investigate the reactions between vanillin and acetic anhydride under basic and acidic conditions by using esterification technique. We used sodium hydroxide as base solution while sulphuric acid as acid solution. In the basic condition, reaction between vanillin that weighed 1.5028 g with 25 mL of 10% sodium hydroxide was produced yellow solution. Then, yellow solution turned to milky white mixture after the addition of 30 g of crushed ice and 4.0 mL of acetic anhydride. After the recrystallization process with warm 95% ethanol, the solid product became shiny. The percentage yield that we got for this product is 77.271%. It is a quite good result because it is more than 75%. The melting point of this product is range from 72 ºC to 75 ºC. It is not purely vanillyl acetate in basic condition because it should need melt from 77 ºC to 79 ºC.

While, the mass of vanillin had been used in acidic condition is 1.5166 g. After addition of 10 drops of 1.0 M sulfuric acid, the mixture had colour changes from colourless solution to red-brick solution. The brick red colour turned to milky white after the addition of 35 mL of ice-cold water. The solid product became shiny after the recrystallization process with warm 95% ethanol. 222.560% was the percentage yield of this product and we could see that we had some error because we had too large the percentage. Maybe the product had weighed during had some moisture in it. 78 ºC to 84 ºC is the melting point of the product. This product should melt from 90 ºC to 91 ºC. Next, we had obtained the reading of IR spectrum of the product which is vanillyl acetate. The IR spectrum indicated that the product was non-purely alcohol because hard to has a large valley centred on the wavenumber 3600 cm-1. The table below shows that the presence of functional group based on their IR spectrum. Functional Group (Wavenumber, cm-1)

Basic Condition

Acidic Condition

Ester (1760 cm-1- 1670 cm-1)

Present

Present

Aromatic Ring (3100 cm-1 - 3000 cm-1)

Present

Present

Alcohol (3600 cm-1 – 3000 cm-1)

Absent

Present

For NMR result, we knew the structure of product and the exact number of hydrogens at a certain signal. The higher the concentration of the signal, the lesser the electron density around it. The table below showed the concentration that have peak for both conditions. Basic Condition

Acidic Condition

1 H, singlet (10 ppm)

1 H, singlet (7.7 ppm)

3 H, singlet (7.2 ppm – 7.5 ppm)

3 H, singlet (7.0 ppm – 7.2 ppm)

3 H, singlet (3.9 ppm)

3 H, singlet (3.9 ppm)

3 H, singlet (1.7 ppm – 2.4 ppm)

9 H, singlet (2.0 ppm – 2.3 ppm)

During the process of this experiment, we might be had some error because we get the percentage yield of vanillyl acetate in acidic condition more than 90%. We can say that the mass of vanillyl acetate had some moisture because of the pressure from Buchner funnel is not good for this experiment. From the melting point of vanillyl acetate in acidic condition also can say that the product was not reacted fully during adding all the solution. So, we need to follow analysis time as it states in procedure to make sure the reaction fully completed.

CONCLUSION: So, we can conclude that we achieved the purpose of this experiment which is to investigate the reactions between vanillin and acetic anhydride under basic and acidic conditions. We also got 77.271% as the percentage yield of the product which is vanillyl acetate in basic condition, while 222.560% is in acidic condition. Finally, we knew the melting point of vanillyl acetate in basic and acidic conditions of reaction are 72 ºC to 75 ºC and 78 ºC to 84 ºC respectively by measuring it.

REFERENCES: 1.

Lab manual CHM556 Organic Chemistry II and also selected pages from Pavia.

2.

https://en.wikipedia.org/wiki/Acetic_anhydride

3.

https://en.wikipedia.org/wiki/Vanillin

CHM 556 ORGANIC CHEMISTRY II

TITLE: ESTERIFICATION REACTIONS OF VANILLIN: THE USE OF NMR TO DETERMINE A STRUCTURE.

NAME AND MEMBERS’ NAME: NAME

STUDENT NO.

GROUP

SITI NURUL AFIQAH BINTI AMINODIN

2017554699

AS2533B3

SAIDATINA AMY BINTI MUSA

2017155489

AS2533A1

NONY HAYATIE BINTI JASNI

2017367257

AS2533B2

DATE OF EXPERIMENT: 10 OCTOBER 2018

DATE OF SUBMISSION: 24 OCTOBER 2018

LECTURER’S NAME: FARIDAHANIM MOHD JAAFAR...