Lab 3 - Experiment #3. Extraction / Separation /...

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CHEM 237 Lab Fall 2009 Objective The purpose of this experiment is to separate a mixture of three compounds based on extraction using acid and base and to identify each of the compounds on TLC. Chemical property of the compounds including polarity and solubility and acid-base reactions involved in the separation of the compounds will be studied. Purity of each compound separated will be checked by TLC, and R 5 10 15 f value of each compound will be calculated. After extractions, each compound in an organic solution will be recovered by complete evaporation of an organic solvent. Isolated yield of each compound will be calculated. Reagents Benzophenone Benzoic acid Benzyl amine 1M HCl (aq) 20 1M NaOH (aq) Ethyl acetate O OH O NH 2 Benzoic acid Benzyl amine Benzophenone (neutral) Apparatus Round bottom flasks (RBF) 25 30 Erlenmeyer flasks Vials Buchner funnel TLC plate (SiO2) Micropipette Graduate Cylinder B ű chner Funnel Separatory funnel Theory Extraction is one of the convenient methods for separation of an organic compound in a mixture. In particular, an acid-base extraction is useful in separating acidic or basic compounds from a mixture based on acidity or basicity of the compounds. For example, benzoic acid and benzyl amine can be readily separated by acid-base extractions. When a mixture of benzoic acid and benzyl amine was treated with base (ex. NaOH solution), benzoic acid containing acidic proton (Lewis acid/Brosted-Lowry acid) will instantly react with a base to generate an organic salt, sodium benzoate which will be soluble in water. However, there will be no reaction between 35 40 45 50 55 benzyl amine (a polar basic compound) and the base. Benzyl amine contains nitrogen with a lone pair of electrons (Lewis base/Bronsted-Lowry base) and will react with acid to produce benzyl ammonium chloride salt which is water-soluble but not soluble in an organic solvent, while no reaction will occur between benzoic acid (soluble in an organic solvent) with the
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Lab 3 - Experiment #3. Extraction / Separation /...

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