Question

What is the purpose of adding cold water in williamson ether reactions

Answer 1

Ether, any of a class of organic compounds characterized by an oxygen atom bonded to two alkyl or aryl groups. Ethers are similar in structure to alcohols, and both ethers and alcohols are similar in structure to water. In an alcohol one hydrogen atom of a water molecule is replaced by an alkyl group, whereas in an ether both hydrogen atoms are replaced by alkyl or aryl groups.

At room temperature, ethers are pleasant-smelling colourless liquids. Relative to alcohols, ethers are generally less dense, are less soluble in water, and have lower boiling points.

A typical Williamson reaction is conducted at 50–100 °C and is complete in 1–8 hours. Often the complete disappearance of the starting material is difficult to achieve, and side reactions are common. Yields of 50–95% are generally achieved in laboratory syntheses, while near-quantitative conversion can be achieved in industrial procedures.

The proton is removed by a suitable base (here a water molecule, ROH is another alternative) to give the ether product.

The Williamson ether synthesis is a reaction that converts alcohols (R-OH) into ethers (R-O-R). The first step in this reaction is forming the conjugate base of the alcohol (called an alcoxide) by reacting the alcohol with sodium metal. This reaction forms hydrogen gas (H₂) as a biproduct, so if you perform this reaction take caution to keep all flame sources away during sodium addition.