Week 6 - Liquid-Liquid Base Extraction of Benzoic Acid from...

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Liquid-Liquid Base Extraction of Benzoic Acid from Acetanilide followed by Recrystallization. Product Identification by Melting Point Determination Mark Gumapas October 25, 2007 Methods and Background The purpose of this lab is to successfully separate a mixture of benzoic acid and acetanilide through extraction with sodium hydroxide, and then to purify the product through recrystillation. To test the identity of the separated products, a melting point experiment will be done to verify a successful experiment. Acetanilide Benzoic Acid The process of extraction involves transferring a solute from one solvent into another due to the greater solubility in the second. The two solvents used must be immiscible and form two distinct layers: organic and aqueous. In this lab, liquid-liquid extraction is used to remove an organic compound from a mixture. It involves distributing a solute between two immiscible liquid. One is the extracting phase, and the other is the original phase. Normally, the immiscible liquids in organic labs are water an organic solvent such as dichloromethane. At a given temperature, the amount of the distributing solute in each phase is expressed quantitatively in terms of the partition coefficient (K). This constant may be obtained by dividing the solubility of the solute in the extracting solvent by the solubility of the solute in the original solvent. Furthermore, the proportion of solute remaining in the original phase after multiple extractions is equal to the volume of original solvent divided by the quantity of K multiplied by the volume of extracting solvent plus the volume of the original solvent, with the whole expression raised to n , the number of extractions performed. From this equation, it can be deduced that multiple extractions become significant as the value of K decreases to increase the quantity of solute extracted. There are certain guidelines for making the correct selection of extracting solvent. The solvent must not react in an irreversible way, it must be immiscible with the original solution, it must selectively remove the desired component, and it should be readily separable from the solute Also in this lab, when we extract our organic solvent from the mixture, it will contain some dissolved water, and it is required to remove this water to make it as pure as possible. It is necessary to dry out the water by using a suitable drying agent. In this case, anhydrous sodium sulfate was used. Carboxylic acids are organic compounds that contain functional groups that are
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Week 6 - Liquid-Liquid Base Extraction of Benzoic Acid from...

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