CHAPTER SIXTEEN Ethers, Epoxides, and Sulfides State ppb xem bew he xc d cata oe ded ition om met ethe is prepared (CH3)C=CH2+ CH3OH (CH3)3 COCH3 tert-Butyl methyl ether is of. Small amounts of tert-butyl methyl ether are added to gasoline as an octane booster. The ten referred to as MTBe daily consumption of gasoline is so high that the demand for tert-butyl methyl ether exceeds our present capacity to produce it. ether. "Remember. italicized PROBLEM 16.5 Outline a reasonable mechanism for the formation of tert-butyl phabetizing, and tert-butyl methyl ether according to the preceding equation The following section describes a versatile method for preparing either symmetri cal or unsymmetrical ethers that is based on the principles of bimolecular nucleophilic 16.6 THE WILLIAMSON ETHER SYNTHESIS is named for A long-standing method for the preparation of ethers is the williamson ether synthesis. Nucleophilic substitution of an alkyl halide by an alkoxide gives the carbon-oxygen bond ritish chemist who used it of an ether: to prepare diethyl ether in R-X ROR+: X Alkoxide Alkyl Ether Halide ion halide Preparation of ethers by the williamson ether synthesis is most successful when the alkyl halide is one that is reactive toward SN2 substitution. Methyl halides and CH3,,CH,ONa CH3 CH, -,, CH,OCH CH3+ Nal Sodium butoxide iodoethane Butyl ethyl ether(71%0) Sodium ethyl ether could be prepared by a williamson ether synthesis n PROBLEM 16.6 Write equations describing two different ways in which benzyl econdary and alkyl halides are not suitable, because they tend to react with alkoxide bases elimination rather than by SN2 substitution. Whether the alkoxide base is primary, secondary, or tertiary is much less important than the nature of the alkyl halide. Thus benzyl isopropyl ether is prepared in high yield from benzyl chloride, a primary chloride that is incapable of undergoing elimination, and sodium iso- CH3)2CHONa CH2Cl—>(CH3)2 CHOCH2 Nacl Sodium Benzyl chloride Benzyl isopropyl ether So chloride Back Forward Main MenuToc Study Guide ToC Student o MHHE WebsiteApproximately 4  109 lb of tert-butyl methyl ether is prepared in the United States each year by the acid-catalyzed addition of methanol to 2-methylpropene: Small amounts of tert-butyl methyl ether are added to gasoline as an octane booster. The daily consumption of gasoline is so high that the demand for tert-butyl methyl ether exceeds our present capacity to produce it. PROBLEM 16.5 Outline a reasonable mechanism for the formation of tert-butyl methyl ether according to the preceding equation. The following section describes a versatile method for preparing either symmetri￾cal or unsymmetrical ethers that is based on the principles of bimolecular nucleophilic substitution. 16.6 THE WILLIAMSON ETHER SYNTHESIS A long-standing method for the preparation of ethers is the Williamson ether synthesis. Nucleophilic substitution of an alkyl halide by an alkoxide gives the carbon–oxygen bond of an ether: Preparation of ethers by the Williamson ether synthesis is most successful when the alkyl halide is one that is reactive toward SN2 substitution. Methyl halides and pri￾mary alkyl halides are the best substrates. PROBLEM 16.6 Write equations describing two different ways in which benzyl ethyl ether could be prepared by a Williamson ether synthesis. Secondary and tertiary alkyl halides are not suitable, because they tend to react with alkoxide bases by E2 elimination rather than by SN2 substitution. Whether the alkoxide base is primary, secondary, or tertiary is much less important than the nature of the alkyl halide. Thus benzyl isopropyl ether is prepared in high yield from benzyl chloride, a primary chloride that is incapable of undergoing elimination, and sodium iso￾propoxide: Sodium isopropoxide (CH3)2CHONa CH2Cl Benzyl chloride (CH3)2CHOCH2 Benzyl isopropyl ether (84%) NaCl Sodium chloride CH3CH2I Iodoethane CH3CH2CH2CH2ONa Sodium butoxide CH3CH2CH2CH2OCH2CH3 Butyl ethyl ether (71%) NaI Sodium iodide RO  Alkoxide ion R X Alkyl halide ROR Ether X Halide ion CH3OH Methanol (CH3)3COCH3 tert-Butyl methyl ether H CH2 (CH3)2C 2-Methylpropene 626 CHAPTER SIXTEEN Ethers, Epoxides, and Sulfides tert-Butyl methyl ether is of￾ten referred to as MTBE, standing for the incorrect name “methyl tert-butyl ether.” Remember, italicized prefixes are ignored when alphabetizing, and tert-butyl precedes methyl. The reaction is named for Alexander Williamson, a British chemist who used it to prepare diethyl ether in 1850. Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website