Chapter 14.2, Problem 14.13P

Interpretation Introduction

Interpretation:

The reagents that has to be used to achieve the given compound via intramolecular Williamson ether synthesis has to be given.

Concept Introduction:

Ether are compounds that contain an oxygen atom that is sandwiched between two R groups.  The R groups may be alkyl, vinyl or aryl.

Alcohols when treated with a very strong base undergo deprotonation to form an alkoxide.  The formed alkoxide ions can acts as a strong nucleophile for the ${\text{S}}_{\text{N}}\text{2}$ reaction.  When an alkoxide and an alkyl halide is combined to form an ether, it is known as Williamson ether synthesis.  Usage of primary alkyl halide is recommended for Williamson ether synthesis because the reaction proceeds via ${\text{S}}_{\text{N}}\text{2}$ mechanism.  If secondary alkyl halides are used, the elimination reaction will predominate over substitution reaction.  Tertiary alkyl halides cannot be used at all because, it undergoes only ${\text{S}}_{\text{N}}\text{1}$ reaction.

The general scheme for Williamson ether synthesis can be given as,

Intramolecular Williamson ether synthesis can also happen when the same compound contains the primary halide and the alkoxide that can be formed upon deprotonation of alcohol.  Cyclic ethers are obtained as product when intramolecular Williamson ether synthesis takes place.