Alcohol Reactions: Williamson Synthesis using NaH, RX, and ROH

The Williamson Synthesis is an SN2 reaction that involves treating an alcohol with a strong base, such as sodium hydride (NaH) to form an alkoxy ion. Then, the alkoxy ion is reacted with an alkyl halide (RX) and an ether is formed:

The carbon chain from the alkyl halide (R) is added to the alcohol group. If the alcohol has a halogen functional group attached, an intramolecular reaction will occur where the OH group will react with its own X group, releasing the X and forming a ring:

SN2 Addition

Intramolecular Reaction

The reaction mechanism is depicted below:

Mechansim

In the first step, lone pair electrons from the alcohol group attack the carbon attached to the halogen of the alkyl halide, causing the carbon-halogen bond to break giving the electrons to the halide ion. This results in the formation of an ether.

There are many reagents used for this reaction but it is often seen with a strong base (NaH, NaOH), a primary or secondary alcohol, and an alkyl halide.

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