Q60E - Organic Chemistry (Mcmurry)

Question

Ethers can often be prepared by SN2 reaction of alkoxide ions,${\mathbf{RO}}^{-}$ , with alkyl halides. Suppose you wanted to prepare cyclohexyl methyl ether. Which of the two possible routes shown below would you choose? Explain.

Step-by-Step Solution

Answer

Step 1: Bimolecular Nucleophilic substitution chemical reaction ( S N 2 )

In a Bimolecular Nucleophilic substitution chemical reaction, substituting an optically active compound with the nucleophile through a backside attack forms the product of inversion stereochemistry.

This reaction occurs in a polar aprotic solvent, e.g., acetone

Step 2: Preparation of Cyclohexyl methyl ether

Cyclohexyl methyl ether is formed by two methods shown as follows:

 

• cyclohexanolate reacted with Iodomethane $\left({\text{S}}_{\text{N}}\text{2 reaction}\right)$ forms the desired product methylcyclohexane, and this is an excellent method of preparing desired ether as Iodomethane is very much reactive in ${\text{S}}_{\text{N}}2$  displacement reaction.

An excellent method for the formation of methoxyhexane
 

• Iodocyclohexane is a secondary haloalkane that reacts with base methoxide ion, forms the substituted product methoxyhexane, and the elimination product cyclohexene. This method forms other side products and the desired product; thus is a less satisfactory method for preparing ether

Less satisfactory method for the formation of methoxyhexane