The Reactions of Ethers

As might be expected from the ability of THF to complex with borane (vide supra), reaction of ethers with electron-deficient species is common and,indeed, the reactions of ethers with electron-deficient species defines most of their chemistry. 

All ethers react with Brpnsted and Lewis acids. Under forcing conditions, most ethers can be induced to fragment into an alkyl halide (or similar) component and alcohol, enol, or phenol. This is the formal reverse of a substitution reaction between 

Problem 8.16. In our present spectroscopic era, how might you determine the presence of an ether functionality in methyl phenyl ether Be as specific as you can. 

The Williamson synthesis cannot, of course, be utilized to prepare ethers under all circumstances. For example, as might be expected, methyl r-butyl ether is readily prepared by the reaction of t-butoxide anion [(CH3)3C- ] with methyl iodide (CH3I) (Equation 8.44), but the same ether cannot be prepared by the reaction of methoxide anion (CHsO ) and 2-iodo-2-methylpropane (f-butyl iodide). 

Problem 8.17. How would you account for the experimental observation that the reaction between methoxide anion (CH3O ) and 2-iodo-2-methylpropane (r-butyl iodide) fails to yield methyl t-butyl ether What do you suppose does happen when these reagents are combined  

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AIH3 is best prepared by the reaction of ethereal solutions of LiAlH4 and AICI3 under very carefully controlled conditions ° ... 

The polar media influences the reaction of peroxyl radicals with ether as on the reaction of two polar reagents [10] and on chain generation by the reaction of ether with dioxygen as reaction with the polar TS. 

More often than not, a halogen atom on the carbon beta to the ether linkage is unreactive. For example, the comparative reactivities of a-and /3-halogens may be illustrated by the reaction of ethers containing both these groups. In each case, the /3-halogen is retained. On the other hand, the bromine atom in /3-ethoxy ethyl bromide,... 

The matter is significant because the reactions of ethers in the coal may proceed along several paths in the strongly basic solution. On the one hand, simple elimination reactions may occur to yield alkoxides and alkenes. 

The reactions of ethers with the titanous-peroxide system are analogous to those of alcohols (Dixon et al., 1964 Kolker, 1964) the predominant spectrum observed is that of the radical derived by abstraction of a hydrogen atom which is a to the ethereal oxygen. The spectrum of the radical derived from dioxan is discussed later. 

Table 5 Deuterium Distribution8 in Percent in Dimethyl Etherb from the Reaction of Ethers with CD2...

Triphenylaluminum etherate can be prepared from PhMgX (X = Cl, Br) in 50-75 % yield, although this is not a convenient procedure (see 5.3.3.3.4). In contrast to trialkylaluminums, the ether can be removed by heating the adduct in vacuo. Pure Ph3Al is also obtained from the reaction of ether-free PhMgBr with AICI3 in dodecane in 75 % yield after recrystallization from xylene . 

However, like alcohols, ethers can be activated by protonation. Ethers, therefore, can undergo nucleophilic substitution reactions with HBr or HI. As with alcohols, the reaction of ethers with hydrogen halides is slow, and the reaction mixture must be heated in order for the reaction to occur at a reasonable rate. 

In general, ethers are unreactive to most chemical reagents. An exception is the reaction of ethers with strong mineral acids such as HI or HBr. The three-membered ring ethers (epoxides or oxiranes), however, are notable... 

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