EPOXY COMPOUND

Newman et al. found that the hydrogenolysis of 1,2-epoxydecane over Raney Ni in ethanol at 150°C and 6.2 MPa H2 gave an approximately 9 1 mixture of 1- 2-decalol, while the ratio was reversed to 1 10-20 when the epoxide was hydrogenated with addition of a small amount of sodium hydroxide.18 In contrast, the course of the hydrogenolysis of styrene oxide was not affected by acid or alkali 2-phenylethanol was always formed preferentially. Mitsui et al. investigated the hydrogenation of 1,2-epoxydecane in detail with nickel wire, Raney Ni, palladium wire, and Pd-C as catalysts in ethanol at 150°C and 6 MPa H2.19 The results summarized in Table 13.1 

TABLE 13.1 Effects of Additives on the Hydrogenation of 1,2-Epoxydccanc over Nickel and Palladium Catalysts3  

Hydrogenation of l,2-epoxy-2-methyloctane (8), carrying the epoxy group attached to a primary carbon and a tertiary carbon, gives selectively the primary alcohol over Raney Ni, while over palladium hydroxide catalyst, the tertiary alcohol is formed in 85% selectivity. In the presence of sodium hydroxide the tertiary alcohol was obtained quantitatively over the palladium catalyst by depressing the formation of other products such as hydrocarbons and carbonyl compounds (eq. 13.6).22 

In the hydrogenation of (Z)- and ( )-4-f-butylmethylenecyclohexane oxides [(Z)-and (Zi)-10] in ethanol at room temperature and 9.8 MPa H2 (eq. 13.7 and Table 13.2), platinum was highly selective for the formation of the tertiary alcohol 11 with (Z)-10, while with (F)-10 the primary alcohol 12 was formed in excess. Over the other transition metals, the tendency to form the primary alcohol was much greater, particularly with (li)-10, where selectivity to the primary alcohol was quantitative over Raney Co, Raney Ni, ruthenium, and palladium. In general, selectivity to produce the primary alcohol over the tertiary alcohol increased in the order Pt Pd Ru, Os, Raney Ni Raney Co. In the case of Pd the major products were hydrocarbons that amounted to 86% with (Z)-10 and 94% with (.E)-10. The amounts of hydrocarbons formed were similarly greater with ( )-10 than with (Z)-10 over the other metals as well. Over Raney Co the primary alcohol that retained the configuration was formed predominantly, while over osmium the primary alcohol with inversed configuration was produced in excess.24 

Accrombessi et al. studied the hydrogenolysis of various epoxycyclohexanes over 10% Pd-C in different solvents at 20° and 1 atm H2.25 The hydrogenolysis of both trans- and cA-l,2-epoxy-4-f-butylcyclohexanes (13 and 14) occurs to give preferentially the axial alcohols by apparent trans addition of hydrogen (eq. 13.8), as evidenced by deuterolysis. 

The application of these findings will need considerable caution until further spectra are available and, in view of the many different groups which can cause absorption near 830 cm and 890 cm , it would be unwise to apply these correlations, other than very tentatively, to compounds not closely similar to those described. 

In addition, Tuot and Barchewitz [12] have suggested that in the overtone region, absorption at 7042 cm may be characteristic of epoxides, but the number of materials examined is small, and this possibility requires further study. 

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Bonding. Surface treatment, such as chemical etch, corona, or flame treatments, is required for adhesive bonding of Tefzel. Polyester and epoxy compounds are suitable adhesives. 

Cost bilizers. In most cases the alkyl tin stabilizets ate particularly efficient heat stabilizers for PVC without the addition of costabilizers. Many of the traditional coadditives, such as antioxidants, epoxy compounds, and phosphites, used with the mixed metal stabilizer systems, afford only minimal benefits when used with the alkyl tin mercaptides. Mercaptans are quite effective costabilizets for some of the alkyl tin mercaptides, particularly those based on mercaptoethyl ester technology (23). Combinations of mercaptan and alkyl tin mercaptide ate currendy the most efficient stabilizers for PVC extmsion processes. The level of tin metal in the stabilizer composition can be reduced by up to 50% while maintaining equivalent performance. Figure 2 shows the two-roU mill performance of some methyl tin stabilizers in a PVC pipe formulation as a function of the tin content and the mercaptide groups at 200°C. 

Cost bilizers. The variety of known costabiHzers for the mixed metal stabilizers is a very long listing. There are, however, a relatively small number of commercially used costabiHzers. Some of these additives can also be added by the PVC compounder or processor ia addition to the stabilizer package to further enhance the desired performance characteristics. The epoxy compounds and phenoHc antioxidants are among the most commonly used costabiHzers with the mixed metal stabilizers. 

Epo>y Compounds. Epoxidized soya oil (ESO) is the most widely used epoxy-type additive and is found ia most mixed metal stabilized PVC formulations at 1.0—3.0 phr due to its versatiHty and cost effectiveness. Other usefiil epoxy compounds are epoxidized glycerol monooleate, epoxidized linseed oil, and alkyl esters of epoxidized tall oil fatty acid. 

The basic metal salts and soaps tend to be less cosdy than the alkyl tin stabilizers for example, in the United States, the market price in 1993 for calcium stearate was about 1.30— 1.60, zinc stearate was 1.70— 2.00, and barium stearate was 2.40— 2.80/kg. Not all of the coadditives are necessary in every PVC compound. Typically, commercial mixed metal stabilizers contain most of the necessary coadditives and usually an epoxy compound and a phosphite are the only additional products that may be added by the processor. The requited costabilizers, however, significantly add to the stabilization costs. Typical phosphites, used in most flexible PVC formulations, are sold for 4.00— 7.50/kg. Typical antioxidants are bisphenol A, selling at 2.00/kg Nnonylphenol at 1.25/kg and BHT at 3.50/kg, respectively. Pricing for ESO is about 2.00— 2.50/kg. Polyols, such as pentaerythritol, used with the barium—cadmium systems, sells at 2.00, whereas the derivative dipentaerythritol costs over three times as much. The P-diketones and specialized dihydropyridines, which are powerful costabilizers for calcium—zinc and barium—zinc systems, are very cosdy. These additives are 10.00 and 20.00/kg, respectively, contributing significantly to the overall stabilizer costs. Hydrotalcites are sold for about 5.00— 7.00/kg. 

Ahphatic polyesters are also available by the chemical reaction of carbon monoxide and formaldehyde (140), carbon dioxide and epoxy compounds... 

Miscellaneous Reactions. Epoxy compounds yield chlorosubstituted carbonates (45). The reaction of chloroformates with hydrogen peroxide or metal peroxides results in the formation of peroxydicarbonates that are used as free-radical initiators of polymerization of vinyl chloride, ethylene, and other unsaturated monomers (46,47). 

The most commonly used stabilizers are barium, cadmium, zinc, calcium and cobalt salts of stearic acid phosphorous acid esters epoxy compounds and phenol derivatives. Using stabilizers can improve the heat and UV light resistance of the polymer blends, but these are only two aspects. The processing temperature, time, and the blending equipment also have effects on the stability of the products. The same raw materials and compositions with different blending methods resulted in products with different heat stabilities. Therefore, a thorough search for the optimal processing conditions must be done in conjunction with a search for the best composition to get the best results. 

Optically pure (S)-benzyl methyl sulfoxide 139 can be converted to the corresponding a-lithio-derivative, which upon reaction with acetone gave a diastereomeric mixture (15 1) of the /S-hydroxysulfoxide 140. This addition reaction gave preferentially the product in which the configuration of the original carbanion is maintained. By this reaction, an optically active epoxy compound 142 was prepared from the cyclohexanone adduct 141181. Johnson and Schroeck188,189 succeeded in obtaining optically active styrene oxide by recrystallization of the condensation product of (+ )-(S)-n-butyl methyl sulfoxide 143 with benzaldehyde. 

The synthesis of an epothilone model system via an alternative C9-C10 disconnection was first examined by Danishefsky in 1997. However, extension of this C9-C10 strategy to a fully functionalized epothilone intermediate was not successful, demonstrating the limitations of RCM with the early catalysts A and B [116]. In 2002, Sinha and Sun disclosed the stereoselective total syntheses of epoA (238a) and epoB (238b) by the RCM of epoxy compounds 242 in the presence of catalyst C (Scheme 50) [117]. The reaction furnished an inconsequential mixture of isomers 243 (E/Z 1 1) in high yield. Subsequent selective hydrogenation of the newly formed double bond followed by deprotection led to epothilones A and B. 

Tops made from solid epoxy compounds are resistant to just about any kind of chemical abuse but are very expensive. They are often sold with an integral backsplash and curved junction, which makes cleaning easy. They are much easier on glassware than either stone or cement composition. 

G. C. Fischer. Corrosion inhibitor compositions containing inhibitor prepared from amino substituted pyrazines and epoxy compounds. Patent US 4895702, 1990. 

Another example of interest with regard to the reaction mechanism is the analysis of epoxy groups. Durbetaki60 titrated a-epoxy compounds with HBr (cf., p. 260) in glacial acetic acid with crystal violet as indicator, but the method was slow for glycidyl esters, CH2—CHCH2OOCR. As it concerns a two-step... 

While dieldrin will, under suitable conditions, exhibit many of the expected reactions of epoxy compounds, it is a remarkably stable oxide. Thus, in its preparation the presence in the oxidizing solution of 1% or more of sulfuric acid in no way affects it. 

Stabilizers Retard degradation Epoxy compounds Organotins Mixed metals... 

On a capillary GC analysis, the separation of positional isomers of epoxy compounds is generally well accomplished by a high polar column, such as DB-23, rather than by a low polar column, such as DB-1. For the positional isomers, a different elution order depending on the kinds of column has not been reported. In the case of two mono epoxides derived from Z6,Z9-dienes, 6,7-epoxides elute slightly faster than 9,10-epoxides [72,170],but the separation is insufficient even on the high polar column. Three monoepoxides derived from Z3,Z6,Z9-trienes elute in the order of 6,7-, 3,4-, and 9,10-epoxides [9]. The former two isomers are sufficiently separated on the high polar column, while the elution of the latter two isomers overlaps [71]. For each positional isomer of diepoxides derived from the Z3,Z6,Z9-trienes, two diastereomeric... 

The stereochemistry of each enantiomer separated by the chiral HPLC has been studied after methanolysis of the epoxy ring. Examining the H NMR data of esters of the produced methoxyalcohols with (S)- and (R)-a-methoxy-a-(tri-fluoromethyl) phenylacetic acid by a modified Mosher s method [181], it has been indicated that the earlier eluting parent epoxides are (3S,4R)-, (6S,7R)-, and (9R,10S)-isomers (Table 7) [75, 76, 179]. The above three chiral HPLC columns show different resolution abilities but a different elution order is not observed. The resolution profile by the reversed-phase OJ-R column has been generalized with molecular shapes of the epoxy compounds considering the... 

Bis-epoxy compounds that have been used for crosslinking purposes vary mainly in their chain length, ranging from the 4-carbon bridge of l,2 3,4-diepoxybutane (Skold, 1983 Kohn et al., 1966), the 6-carbon spacer of l,2 5,6-diepoxyhexane (Fearnley and Speakman, 1950),... 

As mentioned earlier, when NO concentration exceeds that of superoxide, nitric oxide mostly exhibits an inhibitory effect on lipid peroxidation, reacting with lipid peroxyl radicals. These reactions are now well studied [42-44]. The simplest suggestion could be the participation of NO in termination reaction with peroxyl radicals. However, it was found that NO reacts with at least two radicals during inhibition of lipid peroxidation [50]. On these grounds it was proposed that LOONO, a product of the NO recombination with peroxyl radical LOO is rapidly decomposed to LO and N02 and the second NO reacts with LO to form nitroso ester of fatty acid (Reaction (7), Figure 25.1). Alkoxyl radical LO may be transformed into a nitro epoxy compound after rearrangement (Reaction (8)). In addition, LOONO may be hydrolyzed to form fatty acid hydroperoxide (Reaction (6)). Various nitrated lipids can also be formed in the reactions of peroxynitrite and other NO metabolites. 

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