Conversion of Alkyl halides to ethers (SN1)

by James

Description: when dissolved in alcohol solvents, alkyl halides can be converted to ethers through an SN1 reaction.
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Notes: X here is a halide such as Cl, Br, or I (never F). The R group must be able to form a stable carbocation (e.g. tertiary, benzylic or allylic).

In these reactions the alcohol is generally used as the solvent.

Examples: 

Notes: Note that if the alkyl halide is on a stereocenter, that stereocenter will end up as a mixture of configurations (example 3).

Mechanism: Cleavage of the C–Br bond (Step 1, arrow A) leads to a carbocation, which is attacked by the alcohol solvent (Step 2, arrow B). Deprotonation of the oxygen (Step 3, arrows C and D) leads to the ether. This is an SN1 reaction.

Notes: It’s also reasonable to use the alcohol solvent as base in the final step. Note that the fact that a carbocation is involved means that if there is a chiral center, it will end up as a mixture of stereoisomers.

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