Chapter 7.16, Problem 26P

Interpretation Introduction

Interpretation:

Thestereoisomer whichreacts faster in the elimination reaction on treatment with sodium ethoxide in ethanol is to be predicted.

Concept Introduction:

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Dehydrohalogenation reaction is the loss of hydrogen and a halogen from adjacent carbon atoms in an alkyl halide to form the most stable alkene by $\text{β}$ eliminations.

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${\text{E}}_2$ elimination reactions are favored whenever an alkyl halide is treated with a strong base.

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The difference in the reaction rates between the two stereoisomers results from different degrees of $\text{π}$ bond development in the ${\text{E}}_2$ transition state.

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The anti-coplanar arrangement imposes little strain in the ${\text{E}}_2$ transition state, and elimination occurs readily. An absence of anti-coplanar arrangement increases the strain in the ${\text{E}}_2$ transition state, and this slows the rate of elimination.