Chapter 11, Problem 46P

Interpretation Introduction

Interpretation:

The products for the $\text{1,2-addition}$ and the $\text{1,4-addition}$ for the given reactionare to be determined.

Concept Introduction:

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Conjugated dienes are hydrocarbons in which two C=C units are joined by a single bond.

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When a diene is treated with hydrogen halides, two products are formed. In $\text{1,2-addition}$ product, the hydrogen and halogen are added to the adjacent carbon atoms.

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In $\text{1,4-addition}$ product, the hydrogen and halogen are added to the carbon atoms $\text{C1 and C4}$.

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The allylic carbocation is formed preferably during the first protonation step.

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Resonance of this allylic carbocation generates a new carbocation, resulting in the second product.