Ch16 : ROR + HX -> ROH + RX

Chapter 16: Ethers, Epoxides and Sulfides

Cleavage of Ethers by HI or HBr

acid cleavage of ethers

Reaction type: Nucleophilic Substitution

Summary

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 S_N1 or S_N2 like.

QUESTIONS

	If excess HBr is used, what would the products of the reaction be ?	ANSWER
	Is the mechanism shown below S_N1 or S_N2 ?	ANSWER

Related reactions

Reactions of Alcohol with Hydrogen Halides

MECHANISM FOR ACID CLEAVAGE OF ETHERS
Step 1: 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.
Step 2: 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.

© Dr. Ian Hunt, Department of Chemistry