Spectroscopic techniques are commonly used in chemical research to elucidate str

Question

Spectroscopic techniques are commonly used in chemical research to elucidate structures and provide insight into the chemical process. Research on aspartame demonstrates how these tools are used in a research environment. Aspartame, an artificial sweetener, is the methyl ester of the aspartic acid/phenylalanine dipeptide (shown below). Aspartame was originally sold under the trade name NutraSweet and has been safely used to sweeten foods and beverages since 1965. However, upon heating in aqueous solution aspartame undergoes hydrolysis to phenylalanine, aspartic acid and methanol, losing all sweetness. Because of this, aspartame is not recommended to be used in any cooked or heated foods or beverages. Research on the hydrolysis of aspartame focused on the hydrolysis product aspartic acid. Based on its structure, it was proposed that aspartic acid, under hydrolysis conditions, could undergo two additional reactions, deamination and acyl substitution: To test this, a sample of aspartic acid was heated at 100 degree C for 24 hours. The reaction mixture was cooled and the following IR was obtained:

Explanation / Answer

Yes, the deamination reaction has taken place forming fumaric acid.

The acyl substitution product should not have an OH peak, as there is no acid or alcohol. Further, even if it is due to the N-H stretch of primary amine, it should show as a doublet. Moreover, the amine N-H is not as broad and strong as the peaks for acids in that region.

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