Chapter 12, Problem 12.36P

Interpretation Introduction

(a)

Interpretation:

The complete, detailed mechanism and the major product, paying close attention to regiochemistry and stereochemistry is to be drawn for the given reaction.

Concept introduction:

Molecular halogen undergoes anti addition across a $\text{C=C}$ double bond. A halohydrin is produced when an alkene is treated with molecular halogen in water. In the formation of halohydrin from an alkene, the OH group and the halogen atom are anti to each other. In the first step, ${\text{Br}}_{\text{2}}$ is added to an alkene. It is electrophilic addition that produces the halonium ion intermediate. The specific isomer that is formed is dictated by Step 2 of the mechanism— namely, nucleophilic attack by water. ${\text{H}}_{\text{2}}\text{O}$ attacks the side of the ring that acquires greater amount of positive charge. In Step 3, a proton transfer produces the uncharged halohydrin. Regiochemistry becomes an issue with halohydrin formation if the alkene reactant is unsymmetrical. With distinct $\text{C=C}$ atoms, two possible constitutional isomers can be produced depending on which carbon atom ends up bonded to the halogen atom and which carbon atom ends up bonded to the OH group.

Interpretation Introduction

(b)

Interpretation:

The complete, detailed mechanism and the major product, paying close attention to regiochemistry and stereochemistry is to be drawn for the given reaction.

Concept introduction:

Molecular halogen undergoes anti addition across a $\text{C=C}$ double bond. A halohydrin is produced when an alkene is treated with molecular halogen in water. In the formation of halohydrin from an alkene, the OH group and the halogen atom are anti to each other. In the first step ${\text{Br}}_{\text{2}}$ adds to an alkene. It is electrophilic addition that produces the halonium ion intermediate. The specific isomer that is formed is dictated by Step 2 of the mechanism— namely, nucleophilic attack by water. ${\text{H}}_{\text{2}}\text{O}$ attacks the side of the ring that acquires greater amount of positive charge. In Step 3, a proton transfer produces an uncharged halohydrin. Regiochemistry becomes an issue with halohydrin formation if the alkene reactant is unsymmetrical. With distinct $\text{C=C}$ atoms, two possible constitutional isomers can be produced, depending on which carbon atom ends up bonded to the halogen atom and which carbon atom ends up bonded to the OH group.