HBr or HI Cleavage of Ethers

• Used in structural analysis of Ether links

• Net Reaction

  • CH3-O-CH2CH3 + HBr --> CH3OH + CH3CH2Br
  • CH3-O-CH2CH3 + 2HBr --> CH3Br + CH3CH2Br

• With 1 mole HBr the Bromide attaches to the most substituted Carbon(helps spread out positive charge on Oxygen)

• Reaction Mechanism

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Transp 142-Net Reaction

Transp 143- Mechanism

Net Reaction

R-O-R’ + HBr ---> R-OH + R’-Br

R-O-R’ + 2HBr ---> R-Br + R’-Br

Reaction Mechanism(SN2)

1. R-O-R’ + H-Br ---> R-O+-R’ + Br -

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H

2. R-O+-R’ + Br - ---> R-Br + R’OH

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H

3. R’-OH + HBr ---> R’-O+-H2 + Br-

4. R’-O+-H2 + Br - ----> R’-Br + H2O