Preparation of Ether

Williamson's synthesis

In williamson's synthesis, alkyl halides (primary and secondary) react with R'ONa (Sodium alkoxide) or R'OK (Potassium alkoxide) to produce ethers.

Preparation of ether : Williamsons synthesis formula

Tertiary alkyl halides are not used in Williamson's synthesis because tertiary alkyl halides prefer to undergo elimination (example of elimination is given in nucleophilic substitution reaction of haloalakanes ) instead of substitution. Hence, if we are to prepare t-Butyl methyl ether, we will use (CH3)3ONa and CH3Br; and not (CH3)3Br and CH3OH.

Complete the following reaction

Preparation of ether by williomson's synthesis

Preparation of Ethers by Dehydration of Alcohols

When alcohols are heated with conc. H2SO4 at 413 K, ethers (ROR') are formed.

Preparation of ether by dehydration of alcohols

Preparation of Ether using Heated Alumina

The vapours of alcohols are passed over Al2O3 at 513-523 K to produce ether.

Preparation of ether from Al2O3

Preparation of Ether from Alkyl Halides

Alkyl halides are heated with dry silver oxide to form ether.

Preparation of ether from dry silver oxide


Question : Write the reactions of Williamson synthesis of 2-ethoxy-3-methylpentane starting from ethanol and 3-methylpentan-2-ol.

Answer : A primary alkyl halide is preferred in Williamson synthesis because it is less crowded. Thus, the alkyl halide should be derived from ethanol and the alkoxide ion from 3-methylpentan-2-ol.

Alkyl halide is derived from ethanol

Williomsons reactions

Alkoxide ion is derived from 3-methylpentan-2-ol

Williamsons reaction

The Williamson reaction is:

Preparation of 2-ethoxy-3-methylpentane

Preparation of 2-ethoxy-3-methylpentane from williamson synthesis

Question : Write the names of reagents and equations for the preparation of the following ethers by Williamson's synthesis:

  1. 1-Propoxypropane
  2. Ethoxybenzene
  3. 2-Methoxy-2-methylpropane
  4. 1-Methoxyethane

Answer :

  1. Sodium propoxide + 1-Bromopropane → 1-Propoxypropane
  2. Sodium phenoxide + Bromoethane → Ethoxybenzene
  3. Sodium 2-methyl-2-propoxide + Bromoethane → 2-Methoxy-2-methylpropane
  4. Sodium ethoxide + Bromomethane → 1-Methoxyethane