The reaction stops at the phenol stage since the sp 2

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The reaction stops at the phenol stage since the sp 2 carbon of the C-OH bond does not allow the required S N 1 or S N 2 reactions to generate the second molecule of aryl halide. Oxidation of Ethers Ethers may auto-oxidize if left in the presence of oxygen for extended periods of time ( Dangerous in the laboratory). The peroxides and hydroperoxides are unstable and explosive.
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Ch14 Ethers and Epoxides (landscape).docx Page 11 Epoxides Unlike straight chain ethers, epoxides are very reactive ( release of ring strain ), and are useful intermediates because of their chemical versatility. Synthesis Recall alkene and peroxyacid epoxide and carboxylic acid E.g. MCPBA is one of the most common epoxidising reagents. Epoxidations work better for electron rich double bonds.
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Ch14 Ethers and Epoxides (landscape).docx Page 12 Synthesis from Halohydrins When halohydrins are treated with base, an intramolecular cyclisation occurs, and epoxides are formed. Recall that halohydrins are produced from alkenes by reaction with halogens in the presence of water. (Chlorine water or related reagents). Acid Catalyzed ring Opening Epoxides react to release their considerable (25kcal/mol) strain energy. Recall that the acidic hydrolysis of epoxides gives anti diols.
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Ch14 Ethers and Epoxides (landscape).docx Page 13 This overall transformation (alkene anti 1,2-diol) can be achieved in one step by reaction with aqueous peroxyacids. Epoxides can be ring opened by alcohols with acidic catalysis to generate alkoxy alcohols with anti stereochemistry. Hydrohalic Acids Epoxides react with H-X to produce halohydrins , which react further with H-X to generate 1,2-dihalides. (However it is synthetically easier just to add X 2 to an alkene).
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Ch14 Ethers and Epoxides (landscape).docx Page 14 Base Catalyzed Ring Opening
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