Chapter 9, Problem 38P

Interpretation Introduction

(a)

Interpretation: The product formed by the treatment of given alcohol with $\text{HBr}$ is to be drawn and the stereochemistry of product is to be indicated.

Concept introduction: The reaction of alcohols with halogen acids $\left(\text{HX}\right)$ is a general method to obtain $\text{1}\text{°}\text{,}\text{2}\text{°}\text{or}\text{3}\text{°}$ alkyl halides. This method is preferred due to the formation of ${\text{H}}_{\text{2}}\text{O}$ as leaving group. The mechanism of the reaction is ${\text{S}}_{\text{N}}\text{1}$ for $\text{2}\text{°}\text{or}\text{3}\text{°}$ alcohols, and ${\text{S}}_{\text{N}}2$ for $\text{1}\text{°}$ alcohols.

Interpretation Introduction

(b)

Interpretation: The product formed by the treatment of given alcohol with ${\text{PBr}}_{\text{3}}$ is to be drawn and the stereochemistry of product is to be indicated.

Concept introduction: Alkyl bromides are obtained by the reaction of $\text{1}\text{°}\text{or}\text{2}\text{°}$ alcohols with phosphorous tribromide $\left({\text{PBr}}_{\text{3}}\right)$. The reaction yields ${\text{HOPBr}}_{\text{2}}$ as by-product. The mechanism of the reaction involves two steps. The first step is conversion of the $\text{OH}$ group into a good leaving group. The second step is nucleophilic attack by ${\text{Br}}^{-}$ through an ${\text{S}}_{\text{N}}2$ reaction.

Interpretation Introduction

(c)

Interpretation: The product formed by the treatment of given alcohol with $\text{HCl}$ is to be drawn and the stereochemistry of product is to be indicated.

Concept introduction: The reaction of alcohols with halogen acids $\left(\text{HX}\right)$ is a general method to obtain $\text{1}\text{°}\text{,}\text{2}\text{°}\text{or}\text{3}\text{°}$ alkyl halides. This method is preferred due to the formation of ${\text{H}}_{\text{2}}\text{O}$ as leaving group. The mechanism of the reaction is ${\text{S}}_{\text{N}}\text{1}$ for $\text{2}\text{°}\text{or}\text{3}\text{°}$ alcohols, and ${\text{S}}_{\text{N}}2$ for $\text{1}\text{°}$ alcohols.

Interpretation Introduction

(d)

Interpretation: The product formed by the treatment of given alcohol with ${\text{SOCl}}_2$ and pyridine is to be drawn and the stereochemistry of product is to be indicated.

Concept introduction: Alkyl chlorides are obtained by the reaction of $\text{1}\text{°}\text{or}\text{2}\text{°}$ alcohols with thionyl chloride $\left({\text{SOCl}}_2\right)$, and pyridine. The reaction yields ${\text{SO}}_{\text{2}}$, and $\text{HCl}$ as by-products. The mechanism of the reaction involves two steps. The first step is conversion of the $\text{OH}$ group into a good leaving group. The second step is nucleophilic attack by ${\text{Cl}}^{-}$ through an ${\text{S}}_{\text{N}}2$ reaction.