Acids And Aspartame

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The purpose of this experiment was to study the reactions of amino acids and aspartame. Several solutions were prepared and used in TLC analysis. A permanganate test and a ceric nitrate test were also performed. The summary of the results is shown below. TLC Analysis/Rf Values • Plate I o Solution 1: Aspartame Rf: 0.571 o Solution 2: Phenylalanine Rf: 0.571 o Solution 3: Aspartic Acid Rf: 0.217 o Solution 4: Base-hydrolyzed Aspartame Rf: 0.498 • Plate II o Solution 5: Beverage A Rf: 0.519 o Solution 6: Beverage B Rf: 0.535 o Solution 7: Beverage C Rf: 0.388 o Solution 8: Aspartame Rf: 0.519 Permanganate Test Substance Tested Observations Rxn? Fresh Aqueous Aspartame Stayed purple No Solution 4 Brown w/ precipitate Yes Solution 6 Brown Solution 3 had the lowest Rf value because of the polarity of the solutions. Aspartic acid is a charged amino acid, therefore it would have a stronger polarity, resulting in a lower Rf value. Phenylalanine is a hydrophobic amino acid, which is why we observed a relatively high Rf value. A solution of aspartame and hydrolyzed aspartame had relatively high Rf values. Since about 50% of aspartame is made of phenylalanine , the polarity of aspartame is lightly more nonpolar than polar. In plate II, Solution 7 had the lowest Rf value compared to the other solutions, which means it was the most polar Four solutions were tested an out of the four only one had a color change, meaning that it had alcohol present. This solution was methanol and of course it would produce a color change because methanol is an alcohol. One solution that should have changed color was solution 4, the base-hydrolyzed aspartame, but it did not produce a color change when aqueous ceric ammonium nitrate reagent. Water and fresh aqueous aspartame are not going to produce a color change because there is no alcohol group in there structure. An error that occurred in the experiment was during the ceric nitrate test because solution 4 should have produced a color change. During a base hydrolysis of aspartame, aspartic acid, phenylalanine and methanol are produced, therefore the ceric nitrate test should have been a positive for alcohol. A reason that this could have shown a negative result is because methanol is a volatile substance and it could have evaporated out, which would have caused a negative ceric nitrate test

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