CHEM 222 Lab 7

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DEPARTMENT OF CHEMISTRY AND BIOCHEMISTRY CHEM 222 LABORATORY SECTION 04-L TUESDAY AFTERNOON EXPERIMENT 29: BOROHYDRIDE REDUCTION OF VANILLIN TO VANILLYL ALCOHOL Sujay Patel 40283272 Date of Experiment: November 17, 2023 Date of Report Submission: November 24, 2023
Introduction The goal of this experiment is to carry out a reduction reaction of Vanillin into Vanillyl Alcohol using Sodium Borohydride 1 . Afterwards, in order to determine whether the product of the experiment was Vanillyl Alcohol, a melting point test and Infrared Spectrometry must be used, and the results will be compared with the values of the theoretical product. Reaction Techniques - Washing/Drying Solids - Recrystallization - Melting Point - Infrared Spectrometry
Data and Result Table 1: Observations Steps Physical Appearance Colour After the mixture of Vanillin and NaOH Liquid Yellow After the First Addition of Sodium Borohydride Liquid Colourless After More Addition of Sodium Borohydride Liquid/Fizzle Yellow After the Complete Addition of Sodium Borohydride Liquid Dark Yellow During the Addition of HCl Liquid/Precipitation Yellow-White After the First Vacuum Filtration Solid White During the Recrystallization Liquid Colourless After the Recrystallization Liquid with Solids Cloudy-White After the Second Vacuum Filtration Solid/Grains White
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Table 2: Theoretical and Experimental Data Theoretical Experimental Mass of Vanillin Used (g) 3.807 Mass of Borohydride Used (g) 0.501g Mass of Watch Glass (g) 29.554 Mass of Product + Watch Glass (g) 30.969 Mass of Product (g) 3.855 1.415 % Yield of Product 100 36.71 Melting Point (°C) 115 106.7-112.7 Calculations Mass of Crude Product: Mass of WatchGlass = 29.554 g Mass of Crude Product + WatchGlass = 30.969 g Mass of Crude Product = 30.969 g 29.554 = 1.415 g The mass of the crude product is 1.415g
Limiting Reagent: Molar Mass of Vanillin = 152.2 g mol Molar Mass of Sodium Borohydride = 37.38 g mol Molar Mass of Vanillyl Alcohol = 154.3 g mol Mass of Vanillin Used = 3.807 g Mass of SodiumBorohydrideUsed = 0.501 g Mass of Crude Product withVanillin 3.807 g 1 152.2 g mol 4 moles of Vanilyl Alcohol 4 molesof Vanillin 154.2 g mol = 3.852 g Mass of Crude Product with SodiumBorohydride 0.051 g 1 37.38 g mol 4 molesof Vanillin 1 molesof SodiumBorohydride 154.2 g mol = 8.266 g
Limiting Reagent is Vanillin % Yield of Product: Mass of Vanillin Used = 3.807 g Mass of Crude Product = 1.415 g Molar Mass of Vanillin = 152.2 g mol Molar Mass of Vanillyl Alcohol = 154.2 g mol Molesof VanillinUsed = 3.807 g 1 152.2 g mol = 0.0250 moles 4 molesof Vanillin = 4 molesof Vanillin Alcohol 0.0250 molesof Vanillin = 0.0250 moles of Vanillin Alcohol Theoretical Mass of Vanillin Alcohol = 0.0250 moles 154.2 g mol = 3.855 g % Yield of Product = 1.415 g 3.855 g 100 = 36.71% Melting Point Deviation % Theoretical Melting Point = 115 ° C Experimental Melting Point = 112.7 °C
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Deviation % = | 115 112.7 | 115 100 = 2% Infrared Spectrum
Table 3: IR Spectrum Wavelength (cm -1 ) ID Needles 1400-1500 Broad Absorption 3155.60 No Absorption 1660-1750 Strong Absorption 1032.88; 1123.58
Discussion In this experiment, the goal was to carry out a reduction of vanillin into vanillyl alcohol using sodium borohydride. The first step of this experiment was to measure 3.807 g of vanillin in a 125 Erlenmeyer flask. Then, 20 mL of NaOH solvent will be added to the flask. The reason NaOH was used as a solvent is because sodium borohydride, which will be added next, decomposes rapidly when coming in contact with acidic functional groups such as COOH or OH of a phenol. This is why NaOH which is a base can act as a neutralizer while allowing the sodium borohydride to react with the vanillin. The reason alcohol was not used is because it would react with the acidic functional groups in the vanillin and would not allow the sodium borohydride to react with it. The next step of the experiment is to add 0.5g of sodium borohydride. The reason sodium borohydride is used as a reducing agent is because this compound is a mild reducing agent, and it is safe to handle in its solid state. It can also be used in aqueous and alcoholic solutions, unlike LiAlH 4 . The latter is a stronger reducing agent that can react violently with water or other hydroxylic solvents and releases hydrogen gas. The way a reducing agent works is by breaking the C=O bond and adding hydrogen to the missing bonds. Therefore, NaBH 4 can also be used as a reducing agent for acetovanillone or vanillic acid since they both contain a ketone functional group. Finally, in this experiment, an excess of sodium borohydride was used to ensure a complete reaction with all the vanillin in the mixture. Using sodium borohydride in excess can also increase the reaction rate. The third step of this experiment, once the reaction is complete and there is no vanillin remaining, is to remove the excess NaBH 4 from the reaction mixture. Since this compound is a
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strong base, the only way to remove it is to neutralize it with an acid and form a salt. In this case, HCl will be added. This will cause an acid-base reaction and form a precipitate which will contain the product and many impurities. Once the acid-base reaction is complete, it will be vacuum-filtered and only the crude product will remain. The final step of this experiment is to recrystallize the crude product in order to get rid of all of the impurities leaving only the vanillyl alcohol. Therefore, a recrystallization solvent must be used. In this case, the solvent used will be boiling water since vanillyl alcohol is soluble in hot water and not cold water. Therefore, the product will be dissolved completely in hot water. Afterwards, once dissolved, the beaker, in which the solution remains, will be placed in an ice bath which will cool the solution down. Since, vanillyl alcohol is insoluble in water, it will precipitate and form a solid which will be the vanillyl alcohol. Afterwards, once the recrystallization is complete, it will be vacuum filtered leaving only the dry product to be analyzed with infrared spectrometry and melting point. Conclusion In conclusion, the goal of this experiment is to carry out a reduction reaction of vanillin into vanillyl alcohol using sodium borohydride. After the procedures and the analysis of the crude product, it can be said that the product is indeed vanillyl alcohol. Why? Because in this IR spectrum, it can be seen that there are needles at the 1400-1500 cm -1 range indicating the presence of a benzene ring. There is also a broad absorption at 3155.60 cm -1 indicating the presence of an alcohol group. However, what shows that it really is vanillyl alcohol without impurities is that there is no presence of C=O bonds that can be found in the ketone functional
group of vanillin. The second reason of why the product is vanillyl alcohol is because there is only a 2% deviation between the theoretical melting point of vanillyl alcohol and the experimental melting point found which shows that the result is accurate since the percentage is below 5%.
References 1. Wilds, C.J., Robidoux, S. Introductory Organic Chemistry II: Laboratory Manuel Chem 222; Concordia University: Montreal, QC 2. PubChem. https://pubchem.ncbi.nlm.nih.gov/compound/Vanillic-Acid#section=2D- Structure (accessed 2023-11-24) 3. PubChem. https://pubchem.ncbi.nlm.nih.gov/compound/1183 (accessed 2023-11-24) 4. PubChem. https://pubchem.ncbi.nlm.nih.gov/compound/Vanillyl-alcohol (accessed 2023-11-24) 5. PubChem. https://pubchem.ncbi.nlm.nih.gov/compound/2214 (accessed 2023-11-24) 6. Schlesinger, H. I.; Brown, H. C.; Finholt, A. E.; Gilbreath, J. R.; Hoekstra, H. R.; Hyde, E. K. Sodium Borohydride, Its Hydrolysis and Its Use as a Reducing Agent and in the Generation of Hydrogen 1 . J. Am. Chem. Soc. 1953 , 75 (1), 215–219. https://doi.org/10.1021/ja01097a057.
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