CHM 556 ORGANIC CHEMISTRY 2 EXPERIMENT 3: ESTERIFICATION REACTION OF VANILIN (THE USE OF NUCLEAR MAGNETIC RESONANCE AND INFRARED SPECTROSCOPY TO DETERMINE THE STRUCTURE)
NAME: MOHAMAD NOR AMIRUL AZHAR BIN KAMIS (2014647344) PARTNER’S NAME: 1. MOHAMAD SHAFIQ BIN PARMAN 2. MOHAMAD WAFIY BIN MOHD ZULKIFLEE LECTURER’S NAME: Pn. Faridahanim bt Abd Jaafar DATE OF EXPERIMENT: 15/10/2014 DATE OF SUBMISSION: 5/11/2014
EXPERIMENT 3: ESTERIFICATION REACTION OF VANILIN (THE USE OF NUCLEAR MAGNETIC RESONANCE TO DETERMINE THE STRUCTURE) OBJECTIVE: To investigate the esterification reaction between vanillin and acetic anhydride under two conditions, basic and acidic conditions, then measure the melting points, obtain NMR and IR spectra. INTRODUCTION: Vanillin (4-hydroxy-3-methoxybenzaldehyde), a pleasant smelling aromatic compound, occurs naturally in vanilla beans. Vanillin is used widely as a flavouring additive for beverages, cooking and aromatic additive for candles, incense, potpourri, fragrances, perfumes, and air fresheners. The product of reaction between vanillin and acetic anhydride under acidic condition and basic condition will give different product that will be determined by using FTIR and NMR spectrum. Base used in this experiment is sodium hydroxide while acid used is sulphuric acid. PROCEDURE: 1. Acidic condition: i. 1.5g of vanillin was added into a conical flask containing 10mL of acetic acid. ii. 10 drops of 1.0M H2SO4 was added slowly into the solution with stirring. iii. The mixture then was stirred for 1 hour by using magnetic stirrer at room temperature. iv. After the stirring was done, the mixture was placed in cool ice bath for about 4 minutes. v. 35mL of ice cold water was added into the mixture, and was shaken to induce the crystallization. vi. The mixture was filtered by using Buchner funnel to collect the crystal. vii. The crystal was washed with 3 portions of 5mL ice cold water. viii. For recrystallization, 15mL warm ethanol (below 60°C) was added with the crystal collected from the filtration until it dissolved. ix. The mixture was put in ice bath to initiate the recrystallization. x. The mixture was filtered again until dry crystal was obtained. xi. The weight of product was recorded and the melting point, NMR and also IR spectra were tested.
2. Basic condition: i. 1.5g of vanillin was added into a conical flask with 25mL of 10% NaOH solution. ii. 4mL of acetic anhydride and 30g of crushed ice were added into the solution. iii. The mixture was shaken for 20minutes and cloudy, milky white precipitate will form. iv. The mixture then was filtered by using Buchner funnel with washing of 3 portions of 5mL ice-cold water. v. For recrystallization, 15mL warm ethanol (below 60°C) was added with the crystal collected from the filtration until it dissolved. vi. The mixture was put in ice bath to initiate the recrystallization. vii. The mixture was filtered again until dry crystal was obtained. viii. The weight of product was recorded and the melting point, NMR and also IR spectra were tested.
CALCULATION: Mass of vanillin = 1.5g Molar mass of vanillin = 152g/mol Molar mass of vanillin acetate (product) = 194g/mol Mol of vanilin = = 0.009868mol Volume of acetic anhydride = 4mL = 4cm3 Density of acetic anhydride = 1.08g/cm3 Mass of acetic anhydride = 1.08g/cm3 × 4cm3 = 4.32g Mol of acetic anhydride = = 0.04235mol Limiting reactant: vanillin.
RESULT AND OBSERVATION: i.
Fourier Transform Infrared result: Bond
Theoretical wavenumber, cm-1
C=O (aldehyde, ester) 1760-1670 (s) C-O (ester) 1400-1090 (s) C=C (aromatic) 1600,1500 (w-several) C-H (aromatic) 3100-3000 (m) *(b)-broad peak, (s)-sharp peak, (w)-weak.
Experimental wavenumber, cm-1 Acidic 1768.66 1378.98 1611.02,1518.01 3100
Basic 1757.50 1396.59 1599.37,1508.29 3018.77
ii. Nuclear Magnetic Resonance result: 1. Acidic condition Signal 1H, singlet 3H, singlet (benzene) 3H, singlet 9H, singlet
Concentration, ppm 7.7 7.0-7.2 3.9 2.2-2.4
2. Basic condition Signal 1H, singlet 3H,singlet (benzene) 3H, singlet 3H, singlet
Concentration, ppm 10.0 7.4-7.6 3.9 2.4
iii. Observation 1. Acidic condition Colour change from colourless to brick red after the addition of 1.0M of H2SO4 (10drops). The brick red colour turn to milky white after the addition of 35mL of ice cold water. The solid become shiny after the recrystallization process with warm 95% ethanol. 2. Basic condition Reaction between 1.5g vanillin with 25mL of 10% NaOH produce yellow solution. Yellow solution turns to milky white mixture after the addition of 4mL acetic anhydride and 30g crushed ice. The solid become shiny after the recrystallization process with warm 95% ethanol.
Mass of product (acidic condition) = 2.0425g Mass of product (basic condition) = 0.9600g Melting point of product (acidic condition) = 90°C Melting point of product (basic condition) = 79°C Percentage yield =
× 100%
Theoretical yield of acidic condition = 296g/mol × 0.009868mol = 2.9211g Percentage yield in acidic condition =
× 100%
= 69.92% Theoretical yield of basic condition = 194g/mol × 0.009868mol = 1.9145g Percentage yield in basic condition =
× 100%
= 50.14%
Mass of product (g) Theoretical yield (g) Percentage yield (%) Melting point (°C)
Acidic condition 2.0425 2.9211 69.92 90
Basic condition 0.9600 1.9145 50.14 79
DISCUSSION: The percentage yield from both of under acidic condition and basic condition lies above half of the theoretical yield. The loss of the mass of the product may occur during the filtration done by using the Buchner funnel and some of it may be left in the container during the transfer into the Buchner funnel set. In order to get the higher mass of the product, the process of adding solution must be done slowly and always stir the solution. The person in charge also must make sure that the solid that want to dissolve must be completely dissolve before proceeding to the next step. The melting point test was done by using the melting point apparatus. The melting point of both products that was done under acidic and basic condition lies in the range of the theoretical melting point by references. The theoretical melting point of product under acidic condition is between 90-91°C while the theoretical melting point for the product under basic condition is between 77-79°C.
From the FTIR test, the result obtained showed that both of the products have the same several functional groups. The functional groups are C=O bond from aldehyde and ester that lies between 1670-1760cm-1 wavenumber. The C-O bond of ester appears at wavenumber that lie between 1090-1400cm-1. Both of these functional groups have a sharp shape of peak. Weak shape of peaks appears in several at 1500, 1600cm-1 wavenumber that indicate the C=C bond in aromatic ring. The medium shape of peak indicated in both of the compounds is the C-H bond for aromatic ring and it appears in a very small and not strong peak in the spectrum. The structures of the products were tested by using the Nuclear Magnetic Resonance. Some of the peaks are not separated well, so that adjustment must be done to know the exact number of hydrogen at a certain signal. The higher the concentration of the signal, the lesser the electron density around it. Both of them used to have the benzene ring with 3 hydrogen atoms around, that appear around 7ppm in the spectra. For the product under basic condition, it has 2 same signals that are 3H, singlet that lie at different concentration. The first signal with less concentration has high electron density than the second signal that move to the lowfield of the spectrum.
CONCLUSION: The percentage yield under acidic condition is 69.92% and the percentage yield in basic condition is 50.14%. The melting point of product under acidic condition is 79°C and the melting point of product under basic condition is 76°C. Both products show the functional groups of ester and aldehyde from the result of Infrared Spectroscopy and from the NMR result the structure of the products resulting:
Product under acidic condition (4-acetyloxy-3-methoxyphenyl methanediyl diacetate)
Product under basic condition (4-formylphenyl acetate/ vanillyl acetate)
QUESTIONS: 1. Write the mechanism reaction under basic media.
2. Write the mechanism reaction under acidic media.
3. Do they give the same product? No, they give different products between acid media and basic media. 4. What is the function of the base (sodium hydroxide) and acid (sulphuric acid) of the reaction? The function of base and acid used are as the catalyst for the acetylation reaction under basic media and acidic media.
REFERENCES: 1. Acetic anhydride, 27/10/2014, http://en.m.wikipedia.org/wiki/acetic_anhydride 2. CHM 556 Organic Chemistry 2 lecture notes prepared by Prof. Faujan. 3. Department of Chemistry and Biochemistry University Delaware, Synthesis of Vanilin, 24/10/2014, http://valhalla.chem.udel.edu/vanilin.html 4. T.W. Graham Solomons, Craig B. Fryhle, Organic Chemistry, Asia, John Wiley and Sons, 2011.
