3. The kinetics of the acid-catalyzed hydrolysis of the SerTal peptide were studied in methanol, using TFA as the acid. What was measured was the absorbance at \( 220 \mathrm{~nm} \), which is proportional to the concentration of the pepticle; 10 second after adding the TFA and mixing.
\begin{tabular}{|c|c|c|c|c|}
\hline [SerVal] \( (\mu \mathbf{I}) \) & {\( \left[\mathrm{H}_{2} \mathrm{O}\right](\mathrm{mMI}) \)} & {\( [\mathrm{TFA}](\mathrm{M}) \)} & \( A_{220} @ 10 \) seconds & Rate \( (\mathrm{M} / \mathrm{s}) \) \\
\hline 1.0 & 1.0 & 0.05 & 0.95 & \\
\hline 2.0 & 1.0 & 0.05 & 1.91 & \\
\hline 1.0 & 2.0 & 0.05 & 0.94 & \\
\hline 1.0 & 1.0 & 0.10 & 0.47 & \\
\hline
\end{tabular}
Given that the molar absorptivity coefficient of the SerTal pepticle at \( 220 \mathrm{~nm} \) in methanol is \( 1.103 \mathrm{MM}^{-1} \); calculate the rate of reaction for each experiment and then derive the rate law and calculate the rate constant with correct units.
4. The second order rate constant for the acid-catalyzed peptide-forming condensation
\[
\begin{array}{l}
\mathrm{NH}_{3}^{+}-\mathrm{Ala}-\mathrm{CO}_{2}^{-}(\mathrm{aq})+\mathrm{NH}_{3}^{+}-\mathrm{His}^{-\mathrm{CO}_{2}^{-}}(\mathrm{aq}) \xrightarrow{\mathrm{H}^{+}} \\
\mathrm{NH}_{3}{ }^{+}-\mathrm{Ala}-\mathrm{His}-\mathrm{CO}_{2}^{-}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O} \text { (1) } \\
\end{array}
\]
Is \( 0.0075 \frac{\mathrm{L}}{\mathrm{mol} \cdot \mathrm{s}} \). The rate law is \( \frac{d[\text { AlaHis }]}{d t}=k[\mathrm{Ala}]\left[\mathrm{H}^{-}\right] \). If \( 1.50 \mathrm{mM} \) alanine is mixed with \( 7.45 \mathrm{mM} \) histidine and \( 1.50 \mathrm{mM} \mathrm{HCl} \), what is the dipepticle (AlaHis) concentration after 2 hours, assuming no reverse reaction?
D Show Transcribed Text
