Experiment 11: Peptides and Amino Acids
The purpose of this experiment was to study the amino acid composition of artificial sweeteners and then observe simple acid and base catalyzed reactions of the amino acid and artificial sweetener aspartame. This was achieved by performing a TLC analysis using ninhydrin as an indicator to observe the composition of the amino acid as well as two of the components that make up aspartame. This is followed by the addition of an acid or base to aliquots of diet sodas to examine the resulting reactions and compare them to a known hydrolyzed aspartame sample.
The most common method of synthesizing amides is through the reaction of a primary or secondary amine with a carboxylic acid derivative. The resulting bonds can be present as one of two different resonance forms, with the charged resonance form being the most prominent. The two resonance forms are displayed below
Figure 1 …show more content…
When the amide is acid catalyzed the resulting product is a carboxylic acid, and when the amide is base catalyzed then the product is a carboxylate ion. Aspartame, the artificial sugar being analyzed in the experiment, is the dipeptide formed upon the combination of aspartic acid and phenylalanine. The methyl ester is the only part of the compound that is sweet, though it is not completely known why that is the only part that produces a taste. As the amide is hydrolyzed by either an acid or base catalyst, methanol is produced as a byproduct and it is this alcohol byproduct that was tested for using potassium permanganate and ceric ammonium nitrate. The acid catalyzed hydrolysis mechanism for this reaction is pictured
The purpose of this experiment was to study the amino acid composition of artificial sweeteners and then observe simple acid and base catalyzed reactions of the amino acid and artificial sweetener aspartame. This was achieved by performing a TLC analysis using ninhydrin as an indicator to observe the composition of the amino acid as well as two of the components that make up aspartame. This is followed by the addition of an acid or base to aliquots of diet sodas to examine the resulting reactions and compare them to a known hydrolyzed aspartame sample.
The most common method of synthesizing amides is through the reaction of a primary or secondary amine with a carboxylic acid derivative. The resulting bonds can be present as one of two different resonance forms, with the charged resonance form being the most prominent. The two resonance forms are displayed below
Figure 1 …show more content…
When the amide is acid catalyzed the resulting product is a carboxylic acid, and when the amide is base catalyzed then the product is a carboxylate ion. Aspartame, the artificial sugar being analyzed in the experiment, is the dipeptide formed upon the combination of aspartic acid and phenylalanine. The methyl ester is the only part of the compound that is sweet, though it is not completely known why that is the only part that produces a taste. As the amide is hydrolyzed by either an acid or base catalyst, methanol is produced as a byproduct and it is this alcohol byproduct that was tested for using potassium permanganate and ceric ammonium nitrate. The acid catalyzed hydrolysis mechanism for this reaction is pictured