Aspartame, an artificial sweetener, is a peptide and has the following structure:
\begin{matrix} &&&&&& CH _2&-& C _6 H _5 \\ &&&&&& | \\ H _2 N &-& CH &-& CONH &-& CH &-& COOCH _3 \\ && |\\ && CH _2&-& COOH \end{matrix}(i) Identify the four functional groups.
(ii) Write the Zwitter ionic structure.
(iii) Write the structures of the amino acids obtained from the hydrolysis of aspartame.
(iv) Which of the two amino acids is more hydrophobic?
(i) The four functional groups in aspartame are: – NH _2 (amino group), – COOH (carboxyl group),
\begin{matrix} & O &&&& O\\& || &&&& ||\\ -&C&-&NH- \text {(amide group) and} & -& C &- & O- \text {(ester group) }\end{matrix}(ii) The zwitter ionic structure of aspartame is
\begin{matrix} &&&&&& CH _2 C _6 H _5 \\ &&&&&&| \\ H _3 \stackrel{+}{ N } &-& CH &-& CONH &-& CH &-& C &-& OCH _3 \\ &&|&&&&&& || \\ && CH _2 COO ^{-} &&&&&& O\end{matrix}(iii) The hydrolysis of aspartame gives following two amino acids:
(iv)Because of the presence of a large hydrocarbon part, i.e., phenyl group, phenylalanine is more hydrophobic than aspartic acid.