Oxaliplatin, [Pt(dach)(ox)][\text{Pt(dach)(ox)}][Pt(dach)(ox)] (where dach\text{dach}dach is the bidentate neutral ligand trans-1,2-diaminocyclohexane and ox2−\text{ox}^{2-}ox2− is the oxalate bidentate ligand), is a platinum-based chemotherapeutic drug. In the cellular environment, it undergoes activation in a manner similar to cisplatin.
Once inside cancerous cells, oxaliplatin slowly undergoes hydrolysis. In this process, the oxalate ligand is replaced by water molecules to form the active diaqua species, [Pt(dach)(H2O)2]2+[\text{Pt(dach)}(\text{H}_2\text{O})_2]^{2+}[Pt(dach)(H2O)2]2+. Write a balanced equation for this ligand substitution reaction.
State the specific cellular process that is inhibited when the active diaqua platinum complex binds to DNA strands and forms intra-strand cross-links, eventually triggering apoptosis.
Under isothermal conditions, the concentration of oxaliplatin was monitored over the course of the reaction. Describe how graphical methods can be used to analyze these concentration-time data to demonstrate that the hydrolysis is first order with respect to oxaliplatin.
The rate constant kkk for this hydrolysis reaction was measured at several temperatures. The experimental data are presented in the table below:
| Temperature T / KT\ /\ \text{K}T / K | 1T / K−1\frac{1}{T\ } /\ \text{K}^{-1}T 1/ K−1 | Rate constant k / s−1k\ /\ \text{s}^{-1}k / s−1 | lnk\ln klnk |
|---|---|---|---|
| 290290290 | 0.003450.003450.00345 | 7.29×10−107.29 \times 10^{-10}7.29×10−10 | −21.04-21.04−21.04 |
| 300300300 | 0.003330.003330.00333 | 2.37×10−92.37 \times 10^{-9}2.37×10−9 | −19.86-19.86−19.86 |
| 310310310 | 0.003230.003230.00323 | 7.10×10−97.10 \times 10^{-9}7.10×10−9 | −18.76-18.76−18.76 |
| 320320320 | [Value A] | 1.99×10−81.99 \times 10^{-8}1.99×10−8 | [Value B] |
| 330330330 | 0.003030.003030.00303 | 5.25×10−85.25 \times 10^{-8}5.25×10−8 | −16.76-16.76−16.76 |
Calculate the missing numbers [Value A] (to 3 significant figures) and [Value B] (to 2 decimal places).
The temperature dependence of the rate constant can be expressed using the Arrhenius equation:
lnk=−EaRT+lnA \ln k = -\frac{E_a}{RT} + \ln A lnk=−RTEa+lnAA student plotted the data and drew a line of best fit, selecting the following two coordinates from the line:
Determine the gradient of the line of best fit, and use it to calculate the activation energy, EaE_aEa, in kJ mol−1\text{kJ mol}^{-1}kJ mol−1 for this reaction. (The gas constant R=8.31 J K−1 mol−1R = 8.31\ \text{J K}^{-1}\text{ mol}^{-1}R=8.31 J K−1 mol−1).
