CHAPTER SIXTEEN Ethers, Epoxides, and Sulfides A second dangerous property of ethers is the ease with which they undergo oxi- dation in air to form explosive peroxides. Air oxidation of diethyl ether proceeds accord g to the equation CH3 CH,OCH,CH3+ O CH3 CHOCH-CH HOO Diethyl ether Oxygen 1-Ethoxyethyl hydroperoxide The reaction follows a free-radical mechanism and gives a hydroperoxide, a compound of the type ROOH. Hydroperoxides tend to be unstable and shock-sensitive On stand ing, they form related peroxidic derivatives, which are also prone to violent decomposi tion. Air oxidation leads to peroxides within a few days if ethers are even briefly exposed to atmospheric oxygen. For this reason, one should never use old bottles of dialkyl ethers, and extreme care must be exercised in their disposa 16.8 ACID-CATALYZED CLEAVAGE OF ETHERS Just as the carbon-oxygen bond of alcohols is cleaved on reaction with hydrogen halides (Section 4.8), so too is an ether linkage broken RX H Alcohol Hydrogen kyl Water alide ROR′+KXRX+R'OH Ether Hydroge Alcohol The cleavage of ethers is normally carried out under conditions(excess hydrogen halide, heat) that convert the alcohol formed as one of the original products to an alkyl halide. Thus, the reaction typically leads to two alkyl halide molecules ROR′+2HX RX +RX + HO Ether Hydrogen Two alkyl halid halide CH3CHCH, CH3 CH3 CHCH, CH3 CH3 Br sec-Butyl methyl ether 2-Bromobutane (81%) Bromomethane The order of hydrogen halide reactivity is HI> HBr >> HCl. Hydrogen fluoride is not effective PROBLEM 16.9 A series of dialkyl ethers was allowed to react with excess hydro- gen bromide, with the following results Identify the ether in each case (a)One ether gave a mixture of bromocyclopentane and 1-bromobutane (b)Another ether gave only benzyl bromide (ca third ether gave one mole of 1, 5-dibromopentane per mole of ether. Back Forward Main MenuToc Study Guide ToC Student o MHHE WebsiteA second dangerous property of ethers is the ease with which they undergo oxi￾dation in air to form explosive peroxides. Air oxidation of diethyl ether proceeds accord￾ing to the equation The reaction follows a free-radical mechanism and gives a hydroperoxide, a compound of the type ROOH. Hydroperoxides tend to be unstable and shock-sensitive. On stand￾ing, they form related peroxidic derivatives, which are also prone to violent decomposi￾tion. Air oxidation leads to peroxides within a few days if ethers are even briefly exposed to atmospheric oxygen. For this reason, one should never use old bottles of dialkyl ethers, and extreme care must be exercised in their disposal. 16.8 ACID-CATALYZED CLEAVAGE OF ETHERS Just as the carbon–oxygen bond of alcohols is cleaved on reaction with hydrogen halides (Section 4.8), so too is an ether linkage broken: The cleavage of ethers is normally carried out under conditions (excess hydrogen halide, heat) that convert the alcohol formed as one of the original products to an alkyl halide. Thus, the reaction typically leads to two alkyl halide molecules: The order of hydrogen halide reactivity is HI  HBr  HCl. Hydrogen fluoride is not effective. PROBLEM 16.9 A series of dialkyl ethers was allowed to react with excess hydro￾gen bromide, with the following results. Identify the ether in each case. (a) One ether gave a mixture of bromocyclopentane and 1-bromobutane. (b) Another ether gave only benzyl bromide. (c) A third ether gave one mole of 1,5-dibromopentane per mole of ether. ROR Ether 2HX Hydrogen halide H2O Water Two alkyl halides RX R X heat CH3Br Bromomethane OCH3 CH3CHCH2CH3 sec-Butyl methyl ether Br CH3CHCH2CH3 2-Bromobutane (81%) HBr heat ROH Alcohol HX Hydrogen halide H2O Water RX Alkyl halide ROR Ether HX Hydrogen halide ROH Alcohol RX Alkyl halide CH3CH2OCH2CH3 Diethyl ether O2 Oxygen HOO CH3CHOCH2CH3 1-Ethoxyethyl hydroperoxide 628 CHAPTER SIXTEEN Ethers, Epoxides, and Sulfides Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website