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Chapter 12: Problem 77

Assuming that the mechanism for the hydrogenation of \(\mathrm{C}_{2} \mathrm{H}_{4}\) given in Section \(12.7\) is correct, would you predict that the product of the reaction of \(\mathrm{C}_{2} \mathrm{H}_{4}\) with \(\mathrm{D}_{2}\) would be \(\mathrm{CH}_{2} \mathrm{D}-\mathrm{CH}_{2} \mathrm{D}\) or \(\mathrm{CHD}_{2}-\mathrm{CH}_{3} ?\) How could the reaction of \(\mathrm{C}_{2} \mathrm{H}_{4}\) with \(\mathrm{D}_{2}\) be used to confirm the mechanism for the hydrogenation of \(\mathrm{C}_{2} \mathrm{H}_{4}\) given in Section \(12.7 ?\)

Short Answer

Expert verified
Based on the mechanism for the hydrogenation of \(\mathrm{C}_{2}\mathrm{H}_{4}\) given in Section \(12.7\), the predicted product for the reaction of \(\mathrm{C}_{2}\mathrm{H}_{4}\) with \(\mathrm{D}_{2}\) would be \(\mathrm{CH}_{2}\mathrm{D}-\mathrm{CH}_{2}\mathrm{D}\). The reaction supports the mechanism as it demonstrates the catalytic role of the metal surface, the dissociation of diatomic deuterium on the metal surface, and each carbon in the alkene reacting with a deuterium atom, resulting in the formation of \(\mathrm{CH}_{2}\mathrm{D}-\mathrm{CH}_{2}\mathrm{D}\).

Step by step solution

01

Understand the hydrogenation mechanism

First, we need to understand the mechanism for the hydrogenation of \(\mathrm{C}_{2}\mathrm{H}_{4}\). According to Section \(12.7\), the mechanism involves the following steps: 1. The alkene (\(\mathrm{C}_{2}\mathrm{H}_{4}\)) coordinates to the metal surface as the metal acts as a catalyst. 2. A hydrogen molecule (\(\mathrm{H}_{2}\)) dissociates into two hydrogen atoms on the metal surface. 3. A hydrogen atom reacts with one of the carbons of the \(\mathrm{C}_{2}\mathrm{H}_{4}\), and another hydrogen atom reacts with the other carbon. This step results in the alkane product.
02

Determine the reaction mechanism with D₂

To predict the product of the reaction of \(\mathrm{C}_{2}\mathrm{H}_{4}\) with \(\mathrm{D}_{2}\), we can replace the hydrogen atoms with deuterium atoms (\(\mathrm{D}\)) in the mechanism: 1. The alkene (\(\mathrm{C}_{2}\mathrm{H}_{4}\)) coordinates to the metal surface. 2. A deuterium molecule (\(\mathrm{D}_{2}\)) dissociates into two deuterium atoms on the metal surface. 3. A deuterium atom reacts with one of the carbons of the \(\mathrm{C}_{2}\mathrm{H}_{4}\), and another deuterium atom reacts with the other carbon.
03

Determine the product of the reaction of C₂H₄ with D₂

Based on the mechanism described in Step 2, a deuterium atom will react with each carbon in the \(\mathrm{C}_{2}\mathrm{H}_{4}\) molecule. This would lead to the formation of \(\mathrm{CH}_{2}\mathrm{D}-\mathrm{CH}_{2}\mathrm{D}\) as the product of the reaction.
04

Explain how the reaction confirms the mechanism

The observed product of the reaction between \(\mathrm{C}_{2}\mathrm{H}_{4}\) and \(\mathrm{D}_{2}\) confirms the proposed mechanism for the hydrogenation of \(\mathrm{C}_{2}\mathrm{H}_{4}\), as it demonstrates that: 1. The metal surface is catalyzing the reaction, 2. The diatomic deuterium undergoes dissociation on the metal surface, and 3. A deuterium atom reacts with each carbon in the alkene, resulting in the formation of \(\mathrm{CH}_{2}\mathrm{D}-\mathrm{CH}_{2}\mathrm{D}\). If an alternative product such as \(\mathrm{CHD}_{2}-\mathrm{CH}_{3}\) was formed, it would suggest a different reaction mechanism not consistent with the one proposed in Section \(12.7\).

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Most popular questions from this chapter

The central idea of the collision model is that molecules must collide in order to react. Give two reasons why not all collisions of reactant molecules result in product formation.

Consider the reaction $$ 3 \mathrm{~A}+\mathrm{B}+\mathrm{C} \longrightarrow \mathrm{D}+\mathrm{E} $$ where the rate law is defined as $$ -\frac{\Delta[\mathrm{A}]}{\Delta t}=k[\mathrm{~A}]^{2}[\mathrm{~B}][\mathrm{C}] $$ An experiment is carried out where \([\mathrm{B}]_{0}=[\mathrm{C}]_{0}=1.00 M\) and \([\mathrm{A}]_{0}=1.00 \times 10^{-4} M\) a. If after \(3.00 \mathrm{~min},[\mathrm{~A}]=3.26 \times 10^{-5} \mathrm{M}\), calculate the value of \(k\) b. Calculate the half-life for this experiment. c. Calculate the concentration of \(\mathrm{B}\) and the concentration of A after \(10.0 \mathrm{~min}\).

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