vanilla post lab

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University of Southern California *

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105B

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Chemistry

Date

Feb 20, 2024

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pdf

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Uploaded by HighnessFieldLark19

Michele Baek (3528843626) Chem322a – Reduction of Vanillin - Post-Lab • Rf values TLC plate 1: a) 𝑅 ? = ?𝑖?????? ?????𝑙?? ?𝑦 ??𝑙??? ?𝑖?????? ?????𝑙?? ?𝑦 ??𝑙???? = 1.5 3.4 = 0. 44 b) 𝑅 ? = 1.3 3.4 = 0. 38 c) 𝑅 ? = 1.6 3.4 = 0. 47 d) 𝑅 ? = 0.7 3.4 = 0. 21 e) 𝑅 ? = 1.7 3.4 = 0. 5 f) 𝑅 ? = 0.7 3.4 = 0. 21 TLC plate 2: g) 𝑅 ? = 2.1 3.9 = 0. 54 h) 𝑅 ? = 1.7 3.9 = 0. 44 i) 𝑅 ? = 0.8 3.9 = 0. 21 TLC plate 3: j) 𝑅 ? = 1.9 3.2 = 0. 59

k) 𝑅 ? = 1.4 3.2 = 0. 44 l) 𝑅 ? = 0.7 3.2 = 0. 22 m) 𝑅 ? = 1.8 3.2 = 0. 56 n) 𝑅 ? = 1.3 3.2 = 0. 41 o) 𝑅 ? = 0.7 3.2 = 0. 22 p) 𝑅 ? = 0.8 3.2 = 0. 25 Critical Thinking and Analysis . Based on the TLC plates of the starting material and the product, the starting material, vanillin, had a Rf value of 0.44 at 0 seconds. The product material’s Rf value was 0.25. These values can be explainable with the polarity, since the product is more polar than vanillin. Since the starting material vanillin is less polar than the product material, it will travel further and have a higher Rf value than the product since it doesn’t have the ability to stick to the extremely polar TLC plate. On the other hand, the product is polar enough to attract to the plate which explains why it didn’t travel as far enough. The product is more polar because the structure has an oxygen

that is negatively charged, which means that it causes an electron density on the side of the structure, making it very polar. When two TLC plates were completed, it was obvious that the reaction was not complete because the spots at 120 seconds remained the same as before. This shows us that the vanillin and the intermediate were both present in the solution. By adding more sodium borohydride and spotting on the third TLC plate. It showed a completion of the reaction because one spot has disappeared at the end compared to the spotting of the starting material. This proves that the vanillin have all reacted with the sodium borohydride, and therefore, only the product is remaining at the end. One observation from this experiment was that the addition of sodium borohydride to the p-vanillin caused bubbling and fizzing, which proved that a reaction was occurring. 1H NMR spectra for p -vanillin

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1H NMR spectra for p -vanillin and the alcohol

IR spectra for vanillin Conclusion The purpose of performing a reduction reaction by TLC was achieved by collecting three TLC plates that showed the completion of the reaction between p-vanillin and sodium borohydride. The understanding of the difference in polarity between the starting materials and product has been achieved as well by comparing the spotting of the TLC plates at 0 seconds and 120 seconds. The experiment can be improved by carefully taking consideration of chemical contaminations and making sure that the reaction is stirred well to ensure the completion of the reaction. Our experiment showed the completion of the experiment as it visually showed the disappearance of a spot at 120 seconds.