Chapter 7.17, Problem 27P

Interpretation Introduction

Interpretation:

The compound from each of the three pairs that undergoes $\text{E2}$ elimination faster is to be predicted.

Concept Introduction:

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$\text{E2}$ elimination involves the substrate as well as the base in the rate determining step.

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The base extracts a proton in $\text{β-position}$ to the halogen. Simultaneously, the $\text{C}-\text{H}$ bond pair moves to form the $\text{C}-\text{C}$ pi-bond and the halogen (X)leaves along with the $\text{C}-\text{X}$ bond electron pair.

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$\text{E2}$ elimination exhibits (deuterium) the isotope effect because the $\text{C}-\text{H}$ or $\text{C}-\text{D}$ bond is broken in the rate determining step.