Atoms fission and

The report began with the statement that the committee was concerned with the matter of possible military aspects of atomic fission and listed three of those possibilities production of violently radioactive materials. .. carried by airplanes to be scattered as bombs over enemy territory, a power source on submarines and other ships and violently explosive bombs. Radioactive dust would need a year s preparation after the first successful production of a chain reaction, which meant not earlier than 1943. A power source would need at least three years after a chain reaction. Bombs required concentrating U235 or possibly making plutonium in a chain reaction, so atomic bombs can hardly be anticipated before 1945. ... 

Neutron radiation is emitted in fission and generally not spontaneously, although a few heavy radionueleides, e.g. plutonium, undergo spontaneous fission. More often it results from bombarding beryllium atoms with an a-emitter. Neutron radiation deeays into protons and eleetrons with a half-life of about 12 min and is extremely penetrating. 

The rate of decay by spontaneou.s fission increase.s with atomic number and is an important additional cause of instability in the later actinide.s (rrani-Np). 

The diaziridines arc somewhat more stable than the oxaziranes. The three-membered ring of the oxaziranes is decomposed in all of its reactions, but with the diaziridines substitution on the nitrogen atoms can be effected and reactions involving fission and expansion of the ring to a five-membered ring are i)ossiblc,... 

This four-atom replacement was observed in some reactions of uracil derivatives, containing at position 5 a substituent with the CCCN moiety. Treatment of the Z-isomer 5-(2-carbamoylvinyl)-l,3-dialkyluracil with ethanolic sodium ethoxide gave in good yield 3-ethoxycarbonylpyridin-6(lf/)-one (84%) together with 3-A-methylcarbamoyl)pyridin-6-(l7 )-one (10%) (85JOC1513) (Scheme 26). The reaction involves an initial attack of the terminal amino group of the side-chain on position 6 of the uracil molecule. C-6-N-1 bond fission and N-C bond formation yield the pyridin-6(l//)-one. A subsequent attack of the ethoxide ion on the carbonyl groups of the side-chain yields both pyridin-2-one derivatives (Scheme 26). Similar results were obtained with the -isomer. 

We have also observed competition between products resulting from C-C and C-H bond activation in reactions of Y with propene,138 propyne,143 2-butyric,143 four butene isomers,138 acetaldehyde,128 acetone,128 ketene,144 and two cyclohexadiene isomers,145 as well as for Zr, Nb, Mo, and Mo with 2-butyne.143 In this chapter, we use the term C-C activation to describe any reaction leading to C-C bond fission in which the hydrocarbon reactant is broken into two smaller hydrocarbon products, with one hydrocarbon bound to the metal. It is important to note, however, that C-C activation does not necessarily require true C-C insertion. As will be shown in this chapter, the reaction of Y, the simplest second-row transition metal atom, with propene leads to formation of YCH2 +C2H4. The mechanism involves addition to the C=C bond followed by H atom migration and C-C bond fission, rather than by true C-C insertion. 

In mechanism (8.43) the bridgehead hydrogens of barrelene should be found at the a positions of semibullvalene (2a, 0/3,0y). Mechanism (8.44) can give three different hydrogen-label distributions. If the final bond formation is concerted with bond fission, and bond fission and formation take place at the same carbon atom [mechanism (8.44A)], the label distribution should be (la, 0/3, ly). If bond formation is concerted with bond fission but with a preference for bond formation at the carbon allylic to bond fission [mechanism (8.44B)], the label distribution should be (2a, 0/3, Oy). If there is a symmetric allylic biradical which has a finite existence [mechanism (8.44AB)], then the hydrogen-label distribution should be (1.5a, 0/3,0.5y). 

Perhaps the most fruitful of these studies was the radiolysis of HCo(C0)4 in a Kr matrix (61,62). Free radicals detected in the irradiated material corresponded to processes of H-Co fission, electron capture, H-atom additions and clustering. Initial examination at 77 K or lower temperatures revealed the presence of two radicals, Co(C0)4 and HCo(C0)4 , having similar geometries (IV and V) and electronic structures. Both have practically all of the unpaired spin-density confined to nuclei located on the three-fold axis, in Co 3dz2, C 2s or H Is orbitals. Under certain conditions, a radical product of hydrogen-atom addition, H2Co(C0)3, was observed this species is believed to have a distorted trigonal bipyramidal structure in which the H-atoms occupy apical positions. 

Blomeke, J. O. and Todd, M. F. (1958). Uranium-235 Fission-Product Production as a Function of Thermal Neutron Flux, Irradiation Time, and Decay Time. 1. Atomic Concentrations and Gross Totals, Vol. I and II, Part... 

The effectiveness of micellar control on the rate and stereochemical course of hydrolysis at a saturated carbon atom was found to be fairly striking. Chiral 1-methylheptyl trifluoromethanesulfonate [45] undergoes hydrolysis via alkyl-oxygen bond fission, and the hydrolysis rate was only 1/300 (for CTAB) or 1/350 (for SDS) as fast as the rate in pure water (Okamoto et al., 1975). Interestingly, the 2-octanol formed shows net inversion (70%) in a nonmicellar... 

Fig. 5.12. C(6)-Epimerization of the y-lactone degradation products of cefdinir and its 7-epi-mer (5.39a and b, Fig. 5.11). The mechanism involves deprotonation of the enamine N-atom, fission of the dihydrothiazine ring at the C-S bond, followed by reclosure with inversion of... 

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