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
Substance Tested Observations Rxn?
Fresh Aqueous Aspartame Stayed purple No
Solution 4 Brown w/ precipitate Yes
Solution 6 Brown …show more content…
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 …show more content…
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