Alcohols to ethers

Coupling of Alcohols to Ethers the Dominance of the Surface Reaction Pathway ... 

All evidence presented herein points to the generality of the 8 2 path for the surface add-catalyzed coupling of alcohols to ethers. The prc uct composition, the flow from reactants to products, and chirality inversion demonstrate convincingly that mechanistic patterns of the reaction including otygen retention, steric hindrances due... 

Conclusive evidence has been presented that surface-catalyzed coupling of alcohols to ethers proceeds predominantly the S 2 pathway, in which product composition, oxygen retention, and chiral inversion is controlled 1 "competitive double parkir of reactant alcohols or by transition state shape selectivity. These two features afforded by the use of solid add catalysts result in selectivities that are superior to solution reactions. High resolution XPS data demonstrate that Brpnsted add centers activate the alcohols for ether synthesis over sulfonic add resins, and the reaction conditions in zeolites indicate that Brpnsted adds are active centers therein, too. Two different shape-selectivity effects on the alcohol coupling pathway were observed herein transition-state constraint in HZSM-5 and reactant approach constraint in H-mordenite. None of these effects is a molecular sieving of the reactant molecules in the main zeolite channels, as both methanol and isobutanol have dimensions smaller than the main channel diameters in ZSM-S and mordenite. 

Micropulse-type reactors, in catalytic conversion of primary alcohols to ethers, 35 338-... 

Alcohols represent a very versatile class of compounds for organic synthesis, so a variety of synthetic pathways utilize alcohols. Some examples appear in Figure 3-16. The conversion of alcohols to ethers appears later in this chapter. 

When the C—H bond to be oxidized is proximate to a functional group, as we have stated already, its reactivity depends on the type of functional group. In the case of the hydroxy group, especially in secondary alcohols, these are more prone to dioxirane oxidation than their alkane precursors and, consequently, usually carbonyl products are obtained as the final product. Primary alcohols are less reactive, but may still be converted slowly to the corresponding aldehydes or carboxylic acids (due to the facile further oxidation of aldehydes)The functional-group transformation of the alcohols to ethers or acetals reduces the oxidative reactivity " but these C—H bonds are still more reactive than unfunctionalized ones. Thus, dioxirane oxidation of benzyl ether or acetal may... 

Bate equations for the catalytic dehydration of alcohols to ethers... 

In contrast to olefin-forming dehydrations, the transformation of alcohols to ethers very probably includes surface alkoxides as intermediates. It is assumed that one molecule of the alcohol forms the alkoxide which is then attacked by the second alcohol molecule either from the gas phase or from a weakly adsorbed state. Again, cooperation of acidic and basic sites seems to be necessary [116,142,143]. The important step of ether forma-... 

Ternary Critical Point. The point where, upon adding a mutual solvent to two partially miscible liquids (as adding alcohol to ether and water), the two solutions become consolute and one phase results. 

Thus, in theory, a limited quantity of sulphuric acid can convert an unlimited quantity of alcohol to ether, but in practice, owing to side reactions, this does not hold. Sulphuric acid may be replaced by phosphoric, arsenic, or benzene-sulphonic acid. By using a mixture of alcohols mixed ethers may be obtained. Simple ethers are formed simultaneously, however. For mixed ethers it is better to use the methods given on pp. 216, 217. As a catalyst in the above reaction, sand or aluminium sulphate may be employed. The method is applicable to naphthols, but not to phenols. 

Richard has used 50 50 TFE H20 for measurements of /cH by this method and has reported values of p.KR determined in this solvent mixture. The solvent mixture has the slight disadvantage that other measurements refer to water and comparisons suggest that the values in water are more negative by amounts of up to 1 log unit depending on the structure of the cation.69,73,87 Richard used an initial rate method to derive ku, but k can also be obtained by combining the rate constant for approach to equilibrium and the equilibrium ratio of alcohol to ether.88... 

Dehydration of alcohols to ethers, acetals, and ketals Deloxan ASP, Amberlyst Selectivity enhancement Gray et al. (1999)... 

Reactions such as this are significant because new carbon-carbon bonds are formed. It is easy to manipulate various functional groups acids to esters or amides, alcohols to ethers or aldehydes or ketones, etc. But reactions that... 

Scheme 8.3 Conversion of alcohols to ethers—the Williamson ether synthesis.

Upon further examination of the functional group transformations summarized in Figure 8.1, there are a number of additional conversions applicable to the product functional groups. Among these are the conversions of alcohols to ethers illustrated in Scheme 8.3. 

The dehydration of tire aliphatic alcohols to ethers according to the reaction typified in the case of ethanol by ... 

Allyl ethers. Conversion of allylic alcohols to ethers (and ether exchange also) and transpositional allylic methoxylation have been effected by the CAN-ROH sys... 

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