Etherification, commercial reactions

Reaction of olefin oxides (epoxides) to produce poly(oxyalkylene) ether derivatives is the etherification of polyols of greatest commercial importance. Epoxides used include ethylene oxide, propylene oxide, and epichl orohydrin. The products of oxyalkylation have the same number of hydroxyl groups per mole as the starting polyol. Examples include the poly(oxypropylene) ethers of sorbitol (130) and lactitol (131), usually formed in the presence of an alkaline catalyst such as potassium hydroxide. Reaction of epichl orohydrin and isosorbide leads to the bisglycidyl ether (132). A polysubstituted carboxyethyl ether of mannitol has been obtained by the interaction of mannitol with acrylonitrile followed by hydrolysis of the intermediate cyanoethyl ether (133). 

Etherification. The accessible, available hydroxyl groups on the 2, 3, and 6 positions of the anhydroglucose residue are quite reactive (40) and provide sites for much of the current modification of cotton ceUulose to impart special or value-added properties. The two most common classes into which modifications fall include etherification and esterification of the cotton ceUulose hydroxyls as weU as addition reactions with certain unsaturated compounds to produce ceUulose ethers (see Cellulose, ethers). One large class of ceUulose-reactive dyestuffs in commercial use attaches to the ceUulose through an alkaH-catalyzed etherification by nucleophilic attack of the chlorotriazine moiety of the dyestuff ... 

Commercial alkylation is the reaction of isobutane with C3 through Cg olefins in the presence of either sulfuric acid or hydrofluoric acid (see Example 10-1). Etherification is the reaction of a tertiary olefin with an alcohol or water in the presence of an acidic catalyst (see Example 10-2). 

Phenols attached to insoluble supports can be etherified either by treatment with alkyl halides and a base (Williamson ether synthesis) or by treatment with primary or secondary aliphatic alcohols, a phosphine, and an oxidant (typically DEAD Mitsu-nobu reaction). The second methodology is generally preferred, because more alcohols than alkyl halides are commercially available, and because Mitsunobu etherifications proceed quickly at room temperature with high chemoselectivity, as illustrated by Entry 3 in Table 7.11. Thus, neither amines nor C,H-acidic compounds are usually alkylated under Mitsunobu conditions as efficiently as phenols. The reaction proceeds smoothly with both electron-rich and electron-poor phenols. Both primary and secondary aliphatic alcohols can be used to O-alkylate phenols, but variable results have been reported with 2-(Boc-amino)ethanols [146,147]. 

Modification of Textile Fibers. The reaction of hydrophobic chemicals with textile fibers offers the possibUity of permanent repeUency without alteration of the other physical properties of fibers. However, the disadvantages caused by complex processing, and resultant higher costs of carrying out chemical reactions on fiber in commercial textile plant operations, have limited the commercial appHcations. The etherification and esterification of ceUulose have been most effective in terms of achieving durable water repeUency (32,33). Radiation grafting of reactive repeUents onto fibers has been studied as a potential commercial process (34,35), as has modification by plasma polymerization of gas monomers or plasma initiated polymerization of Hquid monomers (36). 

Formation and Cleavage of Ethers in Acidic Media. When alcohols are treated with acids, dehydration (p. 105) or etherification often occurs. Diethyl ether, for example, is prepared commercially by passing ethanol into a mixture of sulfuric acid and alcohol maintained at 140°. By modifying this method somewhat, satisfactory yields of certain mixed ethers have been obtained.4 In other instances etherification proceeds extremely readily. Triphenylcarbinol is etherified by boiling with methanol5 (unless it is carefully freed of traces of acid),6 and benzhydrol is reported to form dibenzhydryl ether by refluxing it with water.7 Again, traces of acid are probably responsible for reaction. 

Figure 1 shows the repeating glucose units of cellulose with the carbons labeled, including those with the reactive 2, 3, and 6 hydroxyls. Ihe most important reactions of cotton cellulose commercially are esterification and etherification, with the products of etherification ranking first. It is generally agreed today among textile scientists that durable press cellulosic textiles ow their smooth-drying and resilient properties to the reactivity of formaldehyde and its amide derivatives with cellulose to produce crosslinks between adjacent cellulose chains (Figure 2). Hovever, the theory that crosslinking was responsible for increased resiliency developed only after the treatmaits were in wide use.

Another important commercial utilization of cotton etherification is in coloration of fabrics with reactive dyes [338 340]. Reactive dyes contain chromophoric groups attached to moieties that have functions capable of reaction with cotton cellulose by nucleophilic addition or nucleophilic substitution to form covalent bonds. In the nucleophilic addition reaction, an alkaline media transforms the reactive dye to an active species by converting the sulfatoethyl-... 

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