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Try The Acid-Base Reaction First

One thing to keep in mind with organic chemistry is that acid-base reactions are fast, relative to most of the other reactions you learn (such as substitution, elimination, addition, etc.). 

Keep this in mind as you see this reaction:

Some students might be tempted to draw the product of an SN2 between HO– and the alkyl halide. It actually would be a mistake to show the alcohol as the product here. [Note here that the “Na” ion is just a “spectator ion” – it doesn’t actually participate in the reaction; NaCl is formed as a byproduct.]

The first thing that happens is that hydroxide ion (HO–) removes a proton from the alcohol to make an alkoxide. Then, the alkoxide (which is a better nucleophile than the alcohol) attacks the alkyl halide to give the ether.

Remember that base makes an alcohol a better nucleophile and acid makes an alcohol a better electrophile. So consider doing the acid-base reaction first. You’ll often find it “sets up” a subsequent reaction.

Thanks for reading! James

P.S. Relevant blog post: Acid Base Reactions Are FAST