Cyclohexane escape

One reactor had been removed for repairs, and the resulting gap was bridged by a temporary 20-in. pipe, connected by a bellows at each end and supported on temporary scaffolding. Tliis pipe collapsed, and in tlic minute or so that elapsed before ignition, about 35 tons of cyclohexane escaped. The extensive damage tliat occurred could liave resulted from tlie deflagration of as little as 10 to 20 tons. 

The exact amount of cyclohexane released is unclear, but it escaped from a system consisting of five reactor vessels containing a total quantity of 250,000 kg (Gugan 1978). However, a complete discharge is unlikely. If an almost complete discharge of the two vessels adjacent to the ruptured pipe is assumed, a total quantity of 100,000 kg of cyclohexane would have been released. 

For example, in the photolysis of (30) in toluene solution, the product of insertion of DPC into the benzylic C—H bonds, 1,1,2-triphenylmethane (31), was accompanied by substantial amounts of 1,1,2,2-tetraphenylethane (32) and bibenzyl (33).When solvents such as cyclohexane are used, tetraphenylethane (32) is formed as the major product, indicating that direct C—H insertion in the singlet state is not the main process in most diarylcarbenes (Scheme 9.7). ° In contrast, 9-cyclohexylfluorene (37) is produced by photolysis of diazofluorene (36) in cyclohexane as a main product (65%) along with a small amount of escaped products (38 and 39). One can estimate in this case that at most 14% of 37 arises from free radical processes. Similarly, direct or sensitized photolysis of diazomalonate in 2,3-dimethylbutane gives C—H insertion products, but in the triplet-sensitized... 

Intermediate metabolites are hydroxylamine (H2NOH) and hydrazine (N2H4). The reaction takes place within internal vesicles known as anammoxosomes. Unusual cyclobutane- and cyclohexane-based lipids in their membranes are thought to partially prevent the escape of the toxic intermediates from the anammoxosomes.614... 

The photochemistry of benzaldehyde (90% 13C=0), 519, deoxybenzoin (99%) 13C=0), 521, and / -chloro benzoin (99% 13C=0), 522, in cyclohexane-Dn solution has been studied633 by spectroscopic techniques, such as XH chemically induced dynamic nuclear634 or electron polarization635 (CIDNP/CIDEP) or dynamic nuclear polarization636 (DNP). In all these cases the formation of benzaldehyde-D with emissive 13C=0 polarization has been observed and the results rationalized by intermolecular hydrogen (deuterium) abstraction by the photoexcited ketones from the solvent molecules and by reactions of cage-escaped radicals (equations 303-308), Benzoin, 520, is formed also. 

Flixborough June 1, 1974 Cyclohexane 400-ton inventory, 40-ton escaped 28 dead, 89 injured... 

The conversion of cyclohexanes to aromatics is a classical dehydrogenation reaction which will readily take place on many transition metals and metal oxides. On chromia-alumina Herington and Eideal (S) have demonstrated the occurrence of cyclo-olefin intermediate products. Weisz and Swegler 25) have demonstrated the effect on benzene yield of allowing early diffusional escape of cyclo-olefin from the porous catalyst particle. Prater et al. 26) have developed evidence that cyclohexene occurs as a quasi-intermediate in aromatization catalysis over platinum catalyst also, although at a smaller concentration, because of a larger ratio of effective rate constants fe/Zci in the scheme... 

Unfortunately, Aj at position 2 of an oxane is not measurable for a substituent with an anomeric effect because steric repulsion cannot be separated experimentally from this effect. Let us look at the CFE in cyclohexane. The example of the methyl group, without the anomeric effect (see Section 2.5), leads us to suppose that the repulsion is greater at this position. We obtain values lower than they are in reality. There are other definitions, but none can escape criticism. 

Hydrogen abstractions by deoxybenzoin from the solvent, undeuterated and perdeuterated cyclohexane, were studied by using stationary l3C CIDNP [96]. As was inferred from the polarizations, the products are formed to a large degree by secondary encounters of escaped radicals. These reactions are accompanied by a-cleavage of the ketone, which is of comparable rate as deuterium abstraction but significantly slower than hydrogen abstraction. 

For these measurements a differential reactor is used which satisfies the same design requirements as the one described above for the cyclohexane test, i.e., for the measurement of a rate constant under well-defined conditions of reactant concentration. The apparatus used has been previously described (5). Cumene, at atmospheric pressure, is passed over a sample of about 20 to 100 mg. of catalyst at a rate of about 2 X 10 moles/sec. at 420°. The catalyst is spread on a flat glass tray of 2 X 5-cm. dimensions (design requirements for products escape and diffusion are less severe than in the case of the cyclohexane test above, since reaction rates are encoim-tered in this reaction from about 0.1 to 10 jumoles/sec./g.) The rate of gas production is used to index the reaction rate and is measured by a mano-metric method (see ref. 2). 

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