Chapter 9, Problem 46P

Interpretation Introduction

(a)

Interpretation: The substitution product (including stereochemistry) formed by the treatment of $\left(\text{R}\right)\text{-hexan-2-ol}$ with the given series of reagent is to be drawn. The two routes that produce identical products are to be identified.

Concept introduction: An alkoxide salt is required to prepare ether. The alkoxide salts are prepared when alcohols are treated with $\text{NaH}$ or ${\text{NaNH}}_{\text{2}}$. The stereochemistry of the product is retention of configuration. However, stereochemistry is reversed when product is allowed to react further with strong nucleophile, like ${\text{I}}^{-}$. It is due to ${\text{S}}_{\text{N}}\text{2}$ path of reaction.

Interpretation Introduction

(b)

Interpretation: The substitution product (including stereochemistry) formed by the treatment of $\left(\text{R}\right)\text{-hexan-2-ol}$ with the given series of reagent is to be drawn.

Concept introduction: Alcohols are converted into alkyl tosylates by treatment with $p\text{-toluenesulfonyl}\text{chloride}\left(\text{TsCl}\right)$ in the presence of pyridine. The overall reaction converts ${}^{-}\text{OH}$ (a poor leaving group) into ${}^{-}\text{OTs}$ (a good leaving group), and stereochemistry of the reaction is retained. However, the further strong nucleophilic attack results the inversion in configuration, through ${\text{S}}_{\text{N}}\text{2}$ mechanism.

Interpretation Introduction

(c)

Interpretation: The substitution product (including stereochemistry) formed by the treatment of $\left(\text{R}\right)\text{-hexan-2-ol}$ with the given series of reagent is to be drawn.

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 is ${\text{S}}_{\text{N}}2$ that results an inversion of configuration product. However, the further strong nucleophilic attack results the inversion in configuration product through ${\text{S}}_{\text{N}}\text{2}$ mechanism.