Lab 6 - Gaurav Singh Brooke Leslie / Dr. Chad Landrie March...

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Gaurav Singh Brooke Leslie / Dr. Chad Landrie March 18, 2009 Lab Six: Liquid-Liquid Base Extraction of Benzoic Acid from Acetanilide followed by Recrystallization. Product Identification by Melting Point Determination. Introduction: The purpose of this experiment is to separate a 1:1 mixture of acetanilide and benzoic acid with a reactive solvent purification of each component through recrystallization through the various methods whose theories are discussed below. Since crystals were successfully isolated and a melting point of the crystalline solid were obtained at the end, the purposes were accomplished and this was a successful lab as a result. Liquid-liquid extraction is one of the most common methods for removing an organic compound from a mixture. This process is used by chemists in the isolation and purification of products from most chemical reactions. The technique involves distributing a solute, A, between two immiscible liquids, the extraction phase and original phase. The process of liquid-liquid extraction can be considered a competition between two immiscible liquids for solute A, with solute A distributing or partitioning between these two liquids when it is in contact with both of them. If K>1, the solute A will be mainly in the extracting solvent so long as the volume of the solvent is at least equal to the volume of the original solvent: the amount of solute remaining in original solvent will depend on the value of K. Increasing the volume of extracting solvent will result in a net increase in the amount of solute in the extracting solvent. If a mixture of a neutral
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and an acidic water-insoluble compound in an organic solvent is shaken with dilute aqueous sodium hydroxide, the acid will dissolve in the aqueous layer, whereas the neutral compound will remain in the organic solvent. After the layers are separated, the acid can be recovered by acidifying the aqueous layer with a strong acid. Thus an acid can easily be separated from neutral or basic contaminants by extraction with aqueous alkali. The purification of the components of the mixture is done through a process of recrystallization. The process of recrystallization involves dissolution of the solid in an appropriate solvent at an elevated temperature and the subsequent re-formation of the crystals upon cooling, so that any impurities remain in solution. An alternative approach involves melting the solid in the absence of solvent and then allowing the crystals to reform so that the impurities are left in the melt. Almost all the solids are more soluble in a hot solvent rather than in a cold
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Lab 6 - Gaurav Singh Brooke Leslie / Dr. Chad Landrie March...

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