Chapter 12, Problem 12.56P

Interpretation Introduction

(a)

Interpretation:

The mechanism that accounts for the formation of the mixture of the products in a given reaction is to be drawn.

Concept introduction:

Electrophilic addition of the molecular chlorine into but-2-ene gives anti-addition of the molecular chlorine via the formation of the chloronium ion as an intermediate. Under similar conditions, molecular chlorine undergoes both syn and anti-addition to $\text{(E)-1-phenylprop-1-ene}$ that produces the isomer plus enantiomers. In order to show both syn and anti-addition, the carbocation like intermediate must be generated. Hence, this electrophilic addition proceeds via formation of stable benzylic carbocation intermediate instead of the formation of chloronium ion. As this reaction leads to formation of two different benzylic carbocation intermediates, the reaction yields four different products which consists of two pairs of enantiomers.

Interpretation Introduction

(b)

Interpretation:

The mechanism for the electrophilic addition of the molecular chlorine to the $\text{1-phenylprop-1-ene}$ is different from the one for $\text{but-2-ene}$ is to be explained.

Concept introduction:

Electrophilic addition of the molecular chlorine into but-2-ene gives anti-addition of the molecular chlorine via the formation of the chloronium ion as an intermediate. Under similar conditions, molecular chlorine undergoes both syn and anti-addition to $\text{(E)-1-phenylprop-1-ene}$ that produces the isomer plus enantiomers. In order to show both syn and anti-addition, the carbocation like intermediate must be generated. Hence, this electrophilic addition proceeds via formation of stable benzylic carbocation intermediate instead of the formation of chloronium ion. As this reaction leads to formation of two different benzylic carbocation intermediates, the reaction yields four different products which consists of two pairs of enantiomers.