The name of the reaction was coined after Alexander William Williamson developed it in 1850. It is a reaction that uses deprotonated alcohol and an organohalide to form ether. It usually take place as an SN2 reaction of a primary alkyl halide with a alkoxide ion. The structure of ethers was proved due to this chemical reaction. Thus organic chemistry’s history holds a special place for the reaction. Read Williamson Ether Synthesis and its uses.
The basic mechanism of the reaction is:
Diethyl Ether and Sodium Chloride are formed when Sodium Ethoxide and Chloroethane a react. The reaction is displayed below:
Na+C2H5O− + C2H5Cl → C2H5OC2H5 + Na+Cl−
The preparation of ethers in labs and industrially is mostly done through this process. Symmetrical and asymmetrical both forms of ethers are simply prepared.
Two choices of reactants are available which is finally agreed upon depending on the reactivity and availability. Two alcohols are also used to produce ethers by Williamson reaction. The two are reacted together after one of them is transformed a leaving group (tosylate).
The alkylating agent is preferred to be primary whereas the alkoxide could be primary secondary or tertiary. If not a Halide, a sulfonate ester created for the reactions purpose are the leaving group.
In situ preparation of alkoxide ions is done as they are extremely reactive. Potassium hydroxide or a carbonate base is used for the laboratory preparation, whereas phase transfer catalysis is used when doing industrial synthesis. Acetonitrile and N, N-dimethylformamide are used as solvents.
It takes around 1-8 hours to complete the reaction and it takes place at a temperature of around 50-100°C. One can get a yield of between 50-95% in the lab preparation as using up the raw material completely is rare, due to side reactions. The industrial procedure shows better quantitative results. Lab synthesis does not usually require a catalyst but if the alkylating agent is unreactive then to improve the rate of reaction iodide salt can be added which yields an extremely reactive iodide after a halide exchange with the chloride. Silver salts like Silver Oxide are used in extreme cases which helps the leaving halide group and makes its exodus more simple.
Practise This Question