Chapter 18, Problem 18.89AP

Interpretation Introduction

(a)

Interpretation:

The mechanism for the formation of vinylic bromide with inversion of configuration by the reaction of vinylic boronic acid with ${\text{Br}}_{\text{2}}$ and $\text{NaOH}$ is to be stated.

Concept introduction:

Electrophilic addition reaction is the substitution of an electrophile at the electron-rich center. The $\text{π-}$ bonds of an alkene make it electron rich which attracts an electron deficient electrophile towards itself and a substitution reaction takes place.

Addition of halogens into alkenes is stereoselective, that is, it depends upon the type of the alkene present. If the alkene is a cis-alkene, anti-addition of halide ions take place and a racemic mixture is formed. If the alkene is a trans-alkene, syn-addition of halide ions occur and a meso compound is formed.

Interpretation Introduction

(b)

Interpretation:

The mechanism for the formation of vinylic iodide with retention of configuration by the reaction of vinylic boronic acid with ${\text{I}}_{\text{2}}$ and $\text{NaOH}$ is to be stated.

Concept introduction:

Electrophilic addition reaction is the substitution of an electrophile at the electron-rich center. The $\text{π-}$ bonds of an alkene make it electron-rich which attracts an electron-deficient electrophile towards itself and a substitution reaction takes place.

Addition of halogens into alkenes is stereoselective, that is, it depends upon the type of the alkene present. If the alkene is a cis-alkene, electron-rich of halide ions takes place and a racemic mixture is formed. If the alkene is a trans-alkene, syn-addition of halide ions occur and a meso compound is formed.