chem 324 - lab 46.pdf - Experiment 46 Preparation of Insect Repellent N,N-Diethyl-meta-toluamide Hang Tran 40044938 CHEM 324 \u2013 Organic Chemistry III

chem 324 - lab 46.pdf - Experiment 46 Preparation of Insect...

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Experiment 46 Preparation of Insect Repellent N,N -Diethyl- meta- toluamide Hang Tran 40044938 CHEM 324 – Organic Chemistry III Concordia University Lab Section: Thursday Afternoon Date Submitted: 31/10/2019
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Introduction The purpose of this experiment is to synthesize N,N-diethyl-m-toluamide. This synthesis consisted of three separate reactions as seen below. The first reaction was a substitution reaction to replace the -OH group of m-toluic acid with a -Cl. The second reaction was the acid-base reaction between diethylamine hydrochloride with NaOH to neutralize the amine salt into a reactive amine. Then, the amine along with the acyl chloride from the first reaction underwent a nucleophilic acyl substitution reaction known as the Schotten-Baumann reaction to form the final product which can also be known as DEET. The Schotten-Baumann reaction is basically one that uses NaOH as a solvent when reacting acyl chlorides. The purpose of this solvent is to neutralize the HCl that is formed during the substitutions. As a result, NaCl and water are formed as by- products of this reaction. Once the final product is formed in solution, it is extracted using liquid- liquid extraction techniques with diethyl ether. The final product will then be purified using column chromatography with alumina and then analyzed by 1 H NMR spectroscopy to confirm its identity. Figure 1: Reaction scheme of this experiment D 20min D 15min
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An important technique used in this experiment is liquid-liquid extraction. This technique is based on the solubility of the product in two immiscible liquids. For this experiment, diethyl ether is used as the organic extraction solvent as it has the ability to dissolve polar and non-polar organic compounds. [1] To perform the separation, the solution with the extraction solvent is added to a separatory funnel and shook to thoroughly mix the liquids. The funnel is then left alone to stand for a period of time to allow for sharp separation between the aqueous phase and the organic phase. Depending on the density of the solvents in the solution relative to water, the denser phase will be at the bottom and the less dense phase will be at the top. Diethyl ether has a density of 0.71 therefore this is the aqueous layer at the bottom. Once a sharp boundary has formed between the organic and aqueous layer, the stopcock of the funnel can be opened to separate the two layers from each other. [1] The layer containing the product is kept and the latter can be rewashed multiple times to ensure complete extraction of the desired product from the solution. Observations The mass of m-toluic acid used was 4.088g The mass of diethylamine HCl used was 2.737g When m-toluic acid was added to thionyl chloride and refluxed, the solution turned yellow The solution of diethylamine and NaOH was clear and colourless
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