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Chapter 16: Ethers, Epoxides and Sulfides
Preparations of Ethers |
Reactions of Ethers |
Preparation of Epoxides |
Reactions of Epoxides |
Spectroscopic Analysis of Ethers |
Self Assessment |
Reactions of Ethers
Ethers, Epoxides and Sulfides
Cleavage of Ethers by HI
Reaction type: Nucleophilic
- Alkyl ethers are cleaved
by the strong acids HI or HBr in a nucleophilic substitution reaction similar
to that of alcohols.
- Protonation of the ethereal
oxygen creates a good leaving group, a neutral alcohol molecule.
- The halide ion, bromide
or iodide are both good nucleophiles.
- Depending on the structure
of the alkyl groups, the reaction can be SN1
or SN2 like.
If excess HBr is used, what would the products of the reaction be ?
Is the mechanism shown below SN1 or SN2 ?
ACID CLEAVAGE OF ETHERS
An acid/base reaction. Protonation of the alcoholic oxygen to make a better
leaving group. This step is very fast and reversible. The lone pairs
on the oxygen make it a Lewis base.
The bromide ion functions as the nucleophile and attacks to displace the
good leaving group, neutral alcohol molecule, by cleaving the C-O
bond. This results in the formation of an alkyl bromide and an alcohol.
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