Radicals ethylene oxide

Trade name Alkyl radical Ethylene oxide Average mol wt. Water solubility ... 

Ethylene oxide is a coproduct, probably formed by the reaction of ethylene and HOO (124—126). Chain branching also occurs through further oxidation of ethylene hydroxyl radicals are the main chain centers of propagation (127). 

This depolymerisation is inherent in the polymer structure and can be prevented by either making a copolymer (such that when un-zipping reaches the co-monomer moiety it is stopped from going any further (e.g., POM (polyoxymethylene) in which a few percent of ethylene oxide has been incorporated), or by using free radical traps (see anti-oxidants). 

A recent study (1) has demonstrated that the electrochemical oxidation of hydroxide ion yields hydroxyl radical ( OH) and its anion (O"-). These species in turn are stabilized at glassy carbon electrodes by transition-metal ions via the formation of metal-oxygen covalent bonds (unpaired d electron with unpaired p electron of -OH and O- ). The coinage metals (Cu, Ag, and Au), which are used as oxygen activation catalysts for several industrial processes (e.g., Ag/02 for production of ethylene oxide) (2-10), have an unpaired electron (d10s1 or d9s2 valence-... 

Regioselective crosslinking of the core domain of cylindrically shaped, wormlike micelles composed of poly[(butadiene)45-b-(ethylene oxide)55] and assembled in aqueous solution at < 5% block copolymer concentrations, was performed using radical coupling of the double bonds throughout the poly(butadiene) phase [27] (Figure 6.3b). This resulted in a 13% reduction in the core diameter, from 14.2 to 12.4 nm, as measured by small-angle neutron scatter-... 

The primary products are methyl and formyl radicals [36, 37] because potential energy surface crossing leads to a H shift at combustion temperatures [35], It is rather interesting that the decomposition of cyclic ethylene oxide proceeds through a route in which it isomerizes to acetaldehyde and readily dissociates into CH3 and HCO. Thus two primary addition reactions that can be written are... 

Photolytic. Grosjean (1997) reported a rate constant of 1.87 x lO " cm /molecule-sec at 298 K for the reaction of 2-ethoxyethanol and OH radicals in the atmosphere. Based on an atmospheric OH radical concentration of 1.0 x 10 molecule/cm , the reported half-life of methanol is 0.35 d (Grosjean, 1997). Stemmier et al. (1996) reported a rate constant of 1.66 x 10 " cm /molecule-sec for the OH radical-initiated oxidation of 2-ethoxyethanol in synthetic air at 297 K and 750 mmHg. Major reaction products identified by GC/MS (with their yields) were ethyl formate, 34% ethylene glycol monoformate, 36% ethylene glycol monoacetate, 7.8% and ethoxyacetaldehyde, 24%. 

The anionic polymerization of epoxides such as ethylene and propylene oxides can be initiated by metal hydroxides, alkoxides, oxides, and amides as well as metal alkyls and aryls, including radical-anion species such as sodium naphthalene [Boileau, 1989 Dreyfuss and Drefyfuss, 1976 Inoue and Aida, 1984 Ishii and Sakai, 1969]. Thus the polymerization of ethylene oxide by M+A involves initiation... 

Mechanisms There is a derth of knowledge about the mechanisms operative in selective oxidation reactions. The only exceptions are the reactions of ethylene to ethylene oxide on supported silver catalysts and of propylene to acrolein on bismuth molybdate type catalysts. For the latter, it is well established through isotopic labeling experiments that a symmetric allyl radical is an intermediate in the reaction and that its formation is rate-determining. Many studies simply extrapolate the results substantiated for this case to other reactions. New ideas on mechanisms are presented by Oyama, et oL, Parmaliana, et aL, and Laszlo. 

The kinetic studies with ethane have established that reaction of C2H.-> radicals with H2 can occur only to a minor extent the only other possible reactions of C2H5 are with 02 to form either ethylene oxide or acetaldehyde, and these can occur only to a small extent. 

With increasing alkyl-substitution, ethylene oxides tend to undergo isomerization to carbonyl compounds before condensation with ilw Organic radical of the Grignard reagent. 10. ... 

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