By the Williamson ether synthesis

Preparation of ethers by the Williamson ether synthesis is most successful with methyl and primary alkyl halides... 

The most generally useful method of preparing ethers is by the Williamson ether synthesis, in which analkoxido ion reacts with a primary alkyl halide or tosylate in an S 2 reaction. As we saw earlier in Section 17.2, thealkoxide ion is normally prepared by reaction of an alcohol with a strong base such as sodium hydride, NaH. 

Thioethers are easily synthesized by the Williamson ether synthesis, using a thiolate ion as the nucleophile. 

Perfluoroalloxy liquid crystals were prepared by the Williamson ether synthesis using perfluoro iodopropene. These materials can be mixed with nematic liquid crystal materials to provide liquid crystal compositions having low viscosity, low refractive index anisotropy, high dielectric anisotropy, and broad nematic phase ranges. 

CXE2C1, C1E3C1, and CXE4C1 were commercially supplied, while CxEsCx and CxEgCx were prepared by the Williamson ether synthesis. The infrared spectra of aqueous solutions of these compounds were measured for various concentrations at room temperature by using a horizontal ATR accessory with a ZnSe prism. Tibe lowest concentration studied was a mole fraction of approximately 0.005. The spectra were recorded on a JASCO FT/IR-7300 spectrometer. Each of the spectra was obtained by the coaddition of 200 scans at a resolution of 4... 

The alkyl allyl ethers used for the catalytic process were obtained from the corresponding sodium alkoxides and allylchloride by the Williamson ether synthesis. Hydrosilylation using triethoxysilane and Speier s catalyst turned out to be a straightforward reaction with yields of 65-85 %, depending on the allyl ethers applied. 

This ether is prepared by the Williamson ether synthesis from alcohols and phenols using a-bromomethylstyrene. It is cleaved by treating the ether in THF with f-BuLi at —78°C for 30 min (75-97% yield). The phenallyl ether can be cleaved in the presence of an allyl ether. Phenallyl amines and amides are cleaved similarly. Cleavage occurs by an addition of the alkyllithium to the olefin followed by elimination. 

PROBLEM 16.7 Only one combination of alkyl halide and alkoxide Is appropriate for the preparation of each of the following ethers by the Williamson ether synthesis. What is the correct combination in each case ... 

Reactions.- Crown lactones are reduced to the corresponding crown ether on reaction with LiAlH at 0°C. The procedure may allow the synthesis of crown ethers which are inaccessible by the Williamson ether synthesis. The reduction of 2,6-pyrido-18-crown-6 N-oxide by (CH CHCHgCH BH appears to involve a single electron transfer as the rate-determining step, followed by transfer of a... 

Show the combination of alcohol and haloalkane that can best be used to prepare each ether by the Williamson ether synthesis. 

Protection of Alcohols. The inherent stability of the MPM ether, coupled with a large repertoire of methods for its removal under mild conditions that do not normally effect other functional groups, makes it a particularly effective derivative for the protection of alcohols. The most common method for its introduction is by the Williamson ether synthesis. A number of bases can be used to generate the alkoxide, but Sodium Hydride in DMF (eq 1) or THF (eq 2) is the most common. Other bases such as n-Butyllithium, Potassium Methylsulfinyl-methylide (dimsylpotassium) (eq 3), and Sodium Hydroxide under phase-transfer conditions are also used. From these results, it is clear that protection can be achieved without interference from Payne rearrangement, and considerable selectivity can be obtained. In the ribose case, selectivity is probably achieved because of the increased acidity of the 2 -hydroxy group. The additive Tetra-n-butylammonium Iodide is used for in situ preparation of the highly reactive p-methoxybenzyl iodide, thus improving the protection of very hindered alcohols. Selective monoprotection of diols is readily occasioned with 0-stannylene acetals. ... 

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