Lab Techniques & Spectroscopy Notes

Lab Techniques & Spectroscopy Notes - Extractions...

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Unformatted text preview: Extractions exploit acid/base properties of organic molecules to separate them.- We can shake a compound of interest with a second solvent (completely immiscible with the first) and allow the two to separate into distinct phases- Liquid-liquid extraction involves this mechanism. Distribution coefficient the ratio of substances solubilities. A water extraction can be accomplished when an organic compound is extracted with water.- Can remove substances that are highly polar or charged (Why? such substances are soluble in water, because water has these properties) Basic compounds (like amines) can be extracted from a mixtures of organic compounds (containing both the basic compound and other given compounds) upon treatment with dilute acid- Usually, the acid will be dilute HCl.- This will protonate the basic functional group, forming a positively charged ion.- The resulting cationic salts of these basic compounds are freely soluble in aqueous solution (i.e. the bottom layer of a separatory funnel) and can be removed from the organic compounds that remain dissolved in the organic phase. We can also use a dilute weak base to separate an acid- Usually the base is NaHCO 3 (sodium bicarbonate)- This results in the formation of an anionic salt.- Dilute NaOH can also be used ( Can be used to convert phenols into their corresponding anionic salts. )- Note: NaOH will also extract carboxylic acids . When we add two solvents to a separatory funnel and place a stopper into the open end, the partial vapor pressures of the two solvents add upon mixing because the vapors of both solvents are not in equilibrium with the solution. We can vent the separatory funnel (it is the apparatus that is turned 90 degrees to allow ventilation to the apparatus)- Should be done multiple times....
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This note was uploaded on 11/07/2010 for the course CBN 356 taught by Professor Merill during the Spring '08 term at Rutgers.

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Lab Techniques & Spectroscopy Notes - Extractions...

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