Ethers, aliphatic hydroxylation

The epoxidation is generally conducted in two steps (/) the polyol is added to epichlorohydrin in the presence of a Lewis acid catalyst (stannic chloride, boron triduoride) to produce the chlorohydrin intermediate, and (2) the intermediate is dehydrohalogenated with sodium hydroxide to yield the aliphatic glycidyl ether. A prominent side-reaction is the conversion of aliphatic hydroxyl groups (formed by the initial reaction) into chloromethyl groups by epichlorohydrin. The aliphatic glycidyl ether resins are used as flexibilizers for aromatic resins and as reactive diluents to reduce viscosities in resin systems. 

Aliphatic glycidyl ethers, 10 376-377 Aliphatic hydrocarbons. See also Aliphatics photochemical chlorination of, 19 113 separation of, 10 782-785 Aliphatic hydroxyl, replacement with chloride, 13 821... 

Although it is a simple matter to attach a single hydroxypropyl residue to a phenolic hydroxyl, the controlled synthesis of chain-extended hydroxypropyl ethers is much more difficult (Fig. 2) (5). The difficulty is that of selectively alkylating an aliphatic hydroxyl on the substrate in the presence of aliphatic hydroxyls on hydroxypropyl groups. Thus we required a method for the preparation of compounds of the type shown in Figure 2 where n is precisely known and controlled (rather than being a statistical range of values). 

Leenheer et al. (1983) have also prepared the trifluoroethyl ethers of humic materials by reaction of a sample suspended in methylene chloride with trifluorodiazoethane. Proton, C, and NMR of this derivative provide information on the concentration of aliphatic hydroxyl groups. 

Shechter and Wynstra ( ) proposed two possible types of reactions between phenol and a glycidyl ether. One involves direct reaction of the phenol with the epoxide the other involves direct reaction of the aliphatic hydroxyl, generated from the epoxide-phenol reaction, with another epoxide as shown in Reactions 22 and 23 ... 

The ether groups, the benzene rings, and, when present, the aliphatic hydroxyls in the cured epoxy system are virtually invulnerable to caustic attack and extremely resistant to acids. In the case of the phenolic resin, the sodium phenolate formed is readily soluble and when present will cause the ultimate disintegration of the resin chain. In the case of the polyester, the ester linkage is hydrolyzed back to the original alcohol and salt of the carboxyl group. The chemical inertness of the cured epoxy system is enhanced by the dense, closely packed structure of the resinous mass, which is extremely resistant to solvent action. 

DPC has in recent years been applied to studies on a range of photopolymers including DF 2000 photopolymer [5], cinnamoylphenyl methacrylate-glycidyl methacrylate copolymer [6], multiethylene glycol dimethacrylate [7], Ebecryl 270 (aliphatic urethane diacrylate) 1,6-hexanediol diacrylate (Darocur 1173 2-hydroxy-2-methyl-phenylpropan-l-one) [8], epoxy acrylates [9], epoxy vinyl ether formulations [10], polyacrylates, maleimides, and vinyl ethers [11], hydroxylated poly(imides) [12], and polystyrene-poly(n-butylacrylate) copolymers [13]. 

Their superior performance is, in essence, due to the basic chemical structure of epoxy. Epoxy resins have very high polarity. The presence of aliphatic hydroxyl and ether groups in the primary resin chain as well as in the cured polymer serve to create an electromagnetic bonding between the epoxy macromolecules and the surface being bonded [239]. 

Because osmium tetroxide is expensive, and its vapors are toxic, alternate methods have been explored for effecting vic-glycol formation. In the aliphatic series, olefins can be hydroxylated with hydrogen peroxide with the use of only a catalytic amount of osmium tetroxide. Anhydrous conditions are not necessary 30% hydrogen peroxide in acetone or acetone-ether is satisfactory. The intermediate osmate ester is presumably cleaved by peroxide to the glycol with regeneration of osmium tetroxide. When this reaction was tried on a A -steroid, the product isolated was the 20-ketone ... 

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