Duong_Experiment8

Duong_Experiment8 - Richard Duong Chem 262L Joseph Sokol 13...

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Richard Duong Chem 262L Joseph Sokol 13 April 2010 Experiment VIII: Electrophilic Aromatic Substitution-Nitration of 4-methylacetanilide and Column Chromatography-Separation of Nitroacetanilides Purpose : In the first part of this experiment, nitration of 4-methylacetanilide (an electrophilic aromatic substitution) will be carried out to form two mono-nitration products. NHCOCH 3 NHCOCH 3 NHCOCH 3 NO 2 NO 2 + HNO 3 Major In the second part of this experiment, the product of the nitration above will be purified using methods of column chromatography. Procedure: An apparatus to remove vapors was set up using an inverted glass funnel (connected to an aspirator) over the mouth of a 10-mL Erlenmeyer flask. 2-mL of 70% nitric acid along with 0.404 g of 4-methyl acetanilide and a stir bar was added to the 10-mL Erlenmeyer and stirred at room temperature for 20 minutes. After the allotted amount of stir time, the solution turned orange. The solution was then poured into 10-mL of ice water, which caused the mixture to
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precipitate yellow solid particles. This yellow product was filtered out quickly using a suction and washing it with five 2-mL portions of ice-cold water. The suction was allowed to run for 7 minutes and then the product was weighed. 0.101 g of the crude product was saved for column chromatography and some was used to find a melting point. Before the column chromatography, a TLC plate was run using the crude product. A small amount of crude product (about a scapula head) was dissolved in 1-mL of dichloromethane. This was done for the starting material also. A third sample of the class’s crude product was also made. A capillary tube was used to transfer small amounts of each sample liquid to a silica-gel TLC plate. The sample starting point was recorded using a pencil and then the TLC plate was developed using a 1:1 hexanes:ethyl acetate solution. Final position was recorded and R f value was recorded after looking under a UV light. Column chromatography was used to purify the product obtained above. A chromatography column attached to a luer tip and stopcock was filled halfway with a 2:1 mixture of hexanes:ethyl acetate solution, which was the solvent. 4.101 g of dry alumina gel was sifted into the column while tapping to remove air. A small amount of sand was added to the column so that it sat above the alumina layer. 0.101 g of crude product saved was dissolved in 0.5-mL of dichloromethane and then poured into the top of the column using a disposable pipette. A beaker was placed below the column to collect the drained liquid and the stop cock was opened until the liquid layer was no longer above the sand layer. The stop cock was closed and the column was filled with the solvent until full. The stop cock was opened again to let the liquid pass, never allowing the liquid layer to go below the alumina layer.
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This document was uploaded on 11/04/2011 for the course CHEM 262 at UNC.

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Duong_Experiment8 - Richard Duong Chem 262L Joseph Sokol 13...

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