Epoxides environmental effects

Haag WR, Mill T. 1988. Effect of a subsurface sediment on hydrolysis of haloalkanes and epoxides. Environmental Science and Technology 22 658-663. 

Thus, as with studies on the double-crested cormorant in the Great Lakes (see Chapter 16 in Walker et al. 2006), there is evidence of a continuing (although reduced) effect of p,p -DDE on reproductive success even after environmental levels had fallen and eggshell thinning was much less. This raises the possibility that p,p -DDE may have had toxic effects other than eggshell thinning on these species (Nisbet 1989). There is the further complication that other OCs such as PCBs, dieldrin, and hep-tachlor epoxide were present in the same samples and may have had toxic effects. 

This Statement was prepared to give you information about heptachlor and heptachlor epoxide and to emphasize the human health effects that may result from exposure to them. The Environmental Protection Agency (EPA) has identified 1,300 hazardous waste sites as the most serious in the nation. These sites comprise the "National Priorities List (NPL) Those sites which are targeted for long-term federal cleanup activities. Heptachlor and heptachlor epoxide have been found in at least 129 and 87 of these sites, respectively. However, we do not know how many of the 1,300 NPL sites have been evaluated for heptachlor and heptachlor epoxide. As EPA evaluates more sites, the number of sites at which heptachlor and heptachlor epoxide are found may change. This information is important for you to know because heptachlor and heptachlor epoxide may cause harmful health effects and because these sites are potential or actual sources of human exposure to heptachlor and heptachlor epoxide. 

The government has been measuring PCB, HCB, DDT, chlordane, heptachlor epoxide and dieldrin since 1998 to identify their effects on wildlife as part of the Environmental Survey on Endocrine Disruptors. The specimens taken include land animals such as raccoons, bears, monkeys and frog, and marine mammals such as seals and whales, in addition to domestic birds and birds of prey. A relatively high concentration of POPs was seen in birds of prey and Phalacrocorax carbo. Eggs of mountain hawk eagles were also found to have a higher concentration of PCB, DDT, heptachlor epoxide, chlordane and dieldrin than other wildlife specimens... 

Silver-alumina type catalysts are by far the most widely used, especially since they are the main catalytic source in the epoxidation of ethylene. Therefore, they are readily available and already have undergone extensive studies. Many systems have sought to utilize the presence of NO (another harmful environmental species) in gas feeds. In this case, the NO species would be reduced to N2, causing oxidation of the hydrocarbon with the support of the catalyst. Studies have helped to elucidate the active species on the catalyst surface at varying temperatures and species leading to the desired products (31). Results from a recent study point to the active silver species being a [Ag O Al] bound intermediate that leads to N2 formation (32). If the silver is present in nanoparticle form, it is simply believed to be a spectator. Other work showed mixed results on the benefit of silver-based alumina systems for the oxidation of methane and higher hydrocarbons. The effect is dependent on the type of reactor system prepared (33,34). 

Nitrous oxide is produced as a byproduct in multimillion Ib/year quantities in nylon manufacture worldwide. Currently, there is a great interest toward the utilization of NjO due to the environmentally hazardous nature of this gas with respect to the greenhouse effect and ozone layer depletion. In addition to their ability to utilize dioxygen for catalytic hydrocarbon oxidations, ruthenium porphyrins have been shown to activate nitrous oxide which is an extremely inert molecule and a poor ligand. Groves and Roman have found that N O reacted with Ru"(TMP)(THF)2 in toluene to produce Ru (TMP)(0)2 . trans-dioxoRu(VI) complex can in turn epoxidize a suitable substrate such as tra/js-p-methyl styrene. This system was subsequently shown to be catalytic under appropriate conditions . 

Since the introduction of the first peptide organocatalyst in the 1980s, a considerable number of new peptide frameworks have been developed that are able to effectively catalyse several important transformations including alcohol esterifications, 1,4-conjugate additions, aldol reactions, Strecker synthesis, asymmetric cyanohydrin synthesis and alkene epoxidation are discussed. A few successful examples of solid-supported peptides and reactions in ball milling under solvent-free conditions have been demonstrated. These methods combine the advantages of being economically and environmentally friendly processes. 

The high solubility of the MTO catalyst in almost any solvent opens up a broad spectrum of reaction media from vhich to choose when performing epoxidations. The most commonly used solvent, however, is still dichloromethane. From an environmental point of view this is certainly not the most appropriate solvent in large scale epoxidations. Interesting solvent effects for the MTO-catalyzed epoxida-tion were reported by Sheldon and coworkers, who performed the reaction in trifluoroethanol [86]. The change from dichoromethane to the fluorinated alcohol allowed for a further reduction of the catalyst loading down to 0.1 mol%, even for terminal alkene substrates. It should be pointed out that this protocol does require 60% aqueous hydrogen peroxide for efficient epoxidations. 

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