Epoxides from ethylenic derivatives

The oxidation of unsaturated compounds by organic peroxy acids in anhydrous solvents such as chloroform, ether, dioxan, benzene, or acetone proceeds with formation of 1,2-epoxides according to the equation  

The following peroxy acids have achieved particular importance for epoxida-tions peroxybenzoic, monoperoxyphthalic, peroxyacetic, and trifluoroperoxy-acetic acid. 

Owing to the sensitivity of the alkene peroxides good yields are obtained only by working at as low reaction temperatures as possible22 and excluding strong acids.23 

Inert solvents are required when using peroxybenzoic or monoperoxyphthalic acid epoxidation by peroxyacetic acid can be carried out in acetic acid as solvent if strong mineral acids (which are often used as catalyst for formation of the peroxy acid) are absent and the reaction temperature is below 30°. 

The epoxides that are the first products of oxidation by peroxyacetic, tri-fluoroperoxyacetic, or, particularly, peroxyformic acid are readily converted into -glycol derivatives. 

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The manufacture and uses of oxiranes are reviewed in (B-80MI50500, B-80MI50501). The industrially most important oxiranes are oxirane itself (ethylene oxide), which is made by catalyzed air-oxidation of ethylene (cf. Section 5.05.4.2.2(f)), and methyloxirane (propylene oxide), which is made by /3-elimination of hydrogen chloride from propene-derived 1-chloro-2-propanol (cf. Section 5.05.4.2.1) and by epoxidation of propene with 1-phenylethyl hydroperoxide cf. Section 5.05.4.2.2(f)) (79MI50501). 

The first report of the copolymerization of an epoxide, namely, ethylene oxide and C02 is contained in a patent by Stevens [6]. However, this process, when carried out in the presence of polyhydric phenols, provided polymers which were viscous liquids or waxes possessing copious polyether linkages with only a few incorporated C02 units. The earliest metal-catalyzed copolymerization of epoxides and C02 was reported in 1969 by Inoue and coworkers, who employed a heterogeneous catalyst system derived from a 1 1 mixture of diethylzinc and H20 [7, 8], Subsequently, Kuran and coworkers investigated a group of related catalysts prepared from diethylzinc and di- and triprotic sources such as pyrogallol, with a slight improvement over Inoue s system for the production of polypropylene carbonate) from PO and C02 [9],... 

Ethylene oxide, the simplest epoxide, is an intermediate in the manufacture of both ethylene glycol, used for automobile antifreeze, and polyester polymers. More than 4 million tons of ethylene oxide is produced each year in the United Slates by air oxidation of ethylene over a silver oxide catalyst at 300 "C. This process is not useful for other ejroxides, however, and is of little value in the laboratory. Note that the name cfhyletie oxide is not a systematic one because Ihe -cue ending implies the presence of a double bond in the molecule. The name is frequently used, however, because ethylene oxide is derived from ethylene by addition of an oxygen atom. Other simple epoxides are named similarly. The systematic name for ethylene oxide is 1,2-epoxyethanc. 

Epoxide rings are cleaved by treatment with acid just as other ethers are. The major difference is that epoxides react under much milder condition-because of ring strain. Dilute aqueous acid at room temperature is sufficiem to cause the hydrolysis of epoxides to 1,2-diols, also called vicina/glycols.(Th word vicinal means adjacent," and a glycol is a diol.) More than 3 millK tons of ethylene glycol, most of it used for automobile antifreeze, are produci each year in the United States by acid-catalyzed hydration of ethylene oxid Note that the name ethylene glycol refers to the glycol derived from ethylen just as ethylene oxide refers to the epoxide derived from ethylene. 

The generation of 3-hydroxypropionitrile from ethylene oxide and HCN in a closed vessel was described in 1878. As the reactivity of epoxides exceeds that of acyclic ethers considerably, oxiranes do represent useful starting materials for hydroxynitriles and their derivatives. For laboratory preparations, the use of alkali metal cyanides (Scheme 13) - instead of HCN will be more convenient. The syntheses of (14) and (15) (Scheme 13) were accomplished in a buffered (MgS04) aqueous solution at about pH 9.5. The intermediate formation of epoxides on treatment of 2-halo alcohols with CN ions has already been mentioned in Section 1.8.1.2.1.ii. 

If we apply the "6/7" rule (see Sachtler (17) for explanation) typically cited as evidence for the role of molecular O2 in selective epoxidation of ethylene for the case of butadiene epoxidation, we would not expect selectivity for epoxybutene to exceed "11/12", or 91.7%. In fact, selectivities of 93-96% are typically seen at all reaction conditions. Selectivities of 97-98% are observed at differential conditions and lower reaction temperatures. Therefore, based only upon the observed selectivities to epoxybutene, dissociatively-adsorbed oxygen is clearly the active oxygen in butadiene epoxidation. Further, the kinetic model, which has been derived from the kinetic plots in Figure 5 has been used to very satisfactorily fit a wide variety of reaction data from several different reactor formats, assumes dissociatively-adsorbed oxygen at both promoted and unpromoted Ag sites. The oxygen incorporated into epoxybutene is dissociatively-adsorbed oxygen, not molecular oxygen. 

In a subsequent simulation study, two important industrial selective oxidation processes were addressed in detail, namely the partial oxidation of methanol to formaldehyde and the epoxidation of ethylene to ethylene oxide. In both cases secondary undesired reactions play a significant role, i.e. the combustion of the primary product in the formaldehyde process and the combustion of the ethylene reactant in the ethylene oxide process, so that the study also provided information on how the adoption of high conductivity monolith catalysts would alfect the selectivity of industrial partial oxidation processes for both a consecutive and a parallel reaction scheme. For both processes intrinsic kinetics applicable to industrial catalysts as well as design and operational parameters for commercial reactors were derived from simulation studies and experimental investigations collected in the literature. 

Epoxy fatty acids occur either as 1,2-epoxy compounds derived from ethylene oxide or 1,4-epoxides derived from furan (fiiran acids). 

Note that the name ethylene oxide is not a systematic one because the -ene ending implies the presence of a double bond in the molecule. The name is frequently used, however, because ethylene oxide is derived from ethylene by addition of an oxygen atom. Other simple epoxides are named similarly. The systematic name for ethylene oxide is 1,2-epoxyethane. 

The poly(alkylene oxide)s are linear or branched-chain polymers that contain ether linkages in their main polymer chain structure and are derived from monomers that are vicinal cyclic oxides, or epoxides, of aliphatic olefins, principally ethylene and propylene and, to a much lesser extent, butylene. These polyethers are commercially produced over a range of molecular weights from a few hundred to several million for use as functional materials and as intermediates. Lower polymers are liquids, increasing in viscosity with molecular weight. The high polymers can be thermoplastic. Solubilities range from hydrophilic water-soluble polymers that are principally derived from ethylene oxide, to hydrophobic, oil-soluble polymers of propylene oxide and butylene oxide. A wide variety of copolymers is produced, both random copolymers and block copolymers. The latter may be used for their surface-active characteristics. 

Epoxidation of cyclooctene and other alkenes with Oxone (KHSO5) was promoted effectively in an aqueous micellar solution of an amphiphilic ketone (3.3).52 The amphiphilic ketone can be easily derived from hepta(ethylene glycol) monodecyl ether. 

The racemic polyzonimine (19) is prepared as shown in Scheme 33. The expoxide (314) is rearranged to the aldehyde (315) by refluxing with LiBr-HMPA in benzene. Morpholine enamine (316) derived from 315 is condensed with nitroethylene, generated in situ from 2-acetoxynitroethane, to afford the nitroaldehyde (317). Ethylene acetalization, reduction over Raney nickel, and subsequent deacetalization give ( )-polyzonimine (19) in 22% overall yield from the epoxide (314) 113). 

In both rats and mice, the radioactivity derived from orally administered 2-cyano-[l,2- 4C]ethylene oxide, the epoxide metabolite of acrylonitrile, was widely distributed to the tissues with no particular acciunulation in any organ and was rapidly depleted within 24 h after dosing (Kedderis et al., 1993b). 

With very few exceptions, quantitative epoxide assay techniques currently in use are derived from the reeotion of ethylene oxides with halogen adds, notably hydrochloric acid and hydrobromio add, in a variety of solvents. Acid uptake may be determined by any of several reliable procedures. These include titration with standard base8 nr back-titration with standard acid.744 The end-point may be detected visually in the presence of suitable acid-base indicators, or by the more precise technique of potontionaetry.447.4 -470 A useful alternative, applicable in the presence of easily hydrolysed substances or of amines that buffer the end-point, is the technique of argentiometry. In this procedure excess of halide ion is titrated with silver nitrate in tV presence of ferric thiocyanate indicator,470 1884 or potentiometri-cally.188 ... 

Etherification with epoxides, such as ethylene oxide or propylene oxide, in aqueous medium in the presence of a basic catalyst yields O-hydroxyalkyl derivatives (11, 12) (Figure 5.6). The degree of substitution varies with the amount of epoxide ranging from 0.1 to 2. As the chain length of the epoxide increases, the water solubility decreases however, small amounts of 2-propanol increase the solubility. 

T < 600 K, it seems quite plausible that ethylene oxide is derived from the thermal decomposition of a lithium alkoxide (most probable propoxide) produced by the (lower temperature) release of C02 from the corresponding Li alkyl carbonate. In fact, the fragments observed for the thermal decomposition of BuOLi were consistent with at least two different epoxides. 

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