Carbon atom, recoil, reactions with

Reactions of the recoil C1] with several olefins have been studied, including ethylene, propylene, cyclopentene, and cfs-butene-2, as well as with several paraffins. The type of products observed indicated the existence of several general modes of interaction, such as CH bond insertion, interactions with CC double bonds, formation of methylene-C11. The most important single product in all systems is acetylene, presumably formed by CH insertion and subsequent decomposition of the intermediate. Direct interaction with double bonds is shown by the fact that, for example, in the case of propylene, yields of stable carbon atom addition products were significantly higher than in the case of propane. The same was true for ethylene and ethane. 

Secondary interference reactions. These are nuclear reactions induced by secondary particles produced in the sample or its immediate environment which will produce the indicator radionuclide by interaction with elements other than the one to be determined. For example, nitrogen is usually determined by the 14N(n, 2n) 13N reaction. The 14 MeV neutrons may generate recoil protons by collision with hydrogen atoms in the vial, transfer tubes, or sample support assembly. These recoil protons may induce the 13C(/, )13N reaction with the carbon of the vial, leading to the formation of the same indicator radionuclide. This type of interference is ordinarily not serious in cases other than the nitrogen determination. 

In 2000, chemists synthesized atoms of Bh (ti 17 s), using the reaction Ne 4n) Bh. Atoms recoiling from the back of the berkelium target were absorbed onto carbon particles suspended in a flow of helium gas and transported to a quartz wool trap in an oven at 1000 °C. There the carbon and the nuclear reaction products were reacted with a mixture of HCl and O2 gases. Some six atoms of bohrium were detected as a volatile oxychloride, believed to be BhOsCl, by analogy with Tc and Re. 

An example of the inferences that have been drawn is as follows. Methylene formation in the reactions of recoiling carbon atoms was deduced from comparison of product distributions from recoil experiments with those obtained from singlet state CH2 (16yl7). The hexanes produced from the reactions of recoiling atoms with n-pentane were... 

Another example involves the soxurce of acetylene as a major product from the reaction of recoiling carbon atoms and cyclopropane (18). MacKay and Wolfgang attributed the formation of acetylene from carbon-atom reactions with alkanes to an insertion into a C—bond followed by fragmentation of the intermediate carbene (18). The hi yield of labeled acetylene from cyclopropane was in accord with this mechanism, since the intermediate cyclopropylmethylene was believed to cleave into two stable molecules ethylene in addition to acetylene. 

Recently these workers have also foimd evidence for formation of chloromethyne, CCl, in reactions of alkyl chlorides with recoiling carbon atoms (6). Chloromethyne, like the fluoromethyne earlier implicated as a reactive intermediate by Wolf (37) and Wolfgang (38), is a species whose reactivity has not been studied in conventional kinetic experiments. 

For carbon atoms, however, the ab initio configuration interaction calculations of Blint and Newton on the reactions of S, D, and P electronic states with molecular hydrogen have made an important contribution (73). A schematic representation of states and pathways is given in Figure 4. The calculations indicate that carbon will not react with H2, a result also obtained by Husain from a symmetry-derived correlation diagram (74). Therefore, the reactions of only the two lowest states of atomic carbon, and P, were considered. The formation of methyne CH from the state and insertion by P recoiling carbon atoms was indicated. 

A natural area of interest for chemists studying high-energy polyvalent atoms is cosmochemistry. With growing indications that high-energy reactions of carbon and silicon atoms are important processes in the formation of interstellar grains, it can be predicted with confidence that the recoil chemistry of polyvalent atoms will claim the attention of cosmochemists and laboratory astrophysicists (129-133). 

The recoil chemistry of carbon-11 in liquid C5-C7 hydrocarbons has been investigated by Clark The recoil atoms have been produced in the (y,n) reaction. The study of the product yields of ethane, ethylene and acetylene (as well as of methane) from different target molecules has been the main concern in this work. Iodine affected the yields of all the volatile products except acetylene. Acetylene-the principal products in all the hydrocarbons investigated, is produced in hot reactions with naked atoms. Insertion of recoil fragments into C—H and C=C bonds leads to various C-labelled hydrocarbons. 

Wolf AP (1960) Labeling of organic compounds by recoil methods. Ann Rev Nud Sci 10 259 Wolf AP (1964) The reactions of energetic tritium and carbon atoms with organic compounds. Adv Phys Organ Chem 2 201... 

The hot-atom chemistry of phosphorus in sulphur and phosphorus compounds, reactor-irradiated in benzene solutions, indicates that a wide range of products is produced. - In one case, greater oxidation of the recoil P is observed in dilute solutions, whereas in the other case thermal reactions of P with carbon atoms dominate for low concentrations but hot reactions seem more important in the higher concentration range. A detailed reaction sequence is given for the phenyl-phosphorus compounds. ... 

This process is known as the Szilard-Chalmers reaction and was discovered when, following the irradiation of ethyl iodide with thermal neutrons, it was found that radioactive iodide could be extracted from the ethyl iodide with water. Moreover, when iodide carrier and silver ions were added to this aqueous phase, the radioactive iodide precipitated as silver iodide. The obvious interpretation of these results is that the neutron irradiation of the ethyl iodide, which caused the formation of ruptured the bonding of this atom to the ediyl group. The bond energy of iodine to carbon in C2H5I is about 2 eV. Since this exceeds the recoil energies of neutron capture, the bond breakage must have resulted from the 7-emission which followed neutron capture and not the capture process itself. The reaction can be written ... 

An interesting application of Husain s kinetic data to the interpretation of the results of a recoil experiment have been made by Kremer and Spicer (10). These workers studied the exchange reactions of sulfur atoms with carbon disulfide. 

Radioactive carbon can be produced through various nuclear reactions (Stocldin 1969 Tachikawa 1975). Carbon-11 hot atom reactions are relatively known. Wolfgang (1965) postulated that recoil was obtained by neutron abstraction reaction of carbon and this energetic carbon could be led into a reaction chamber filled with organic gases. The state of in the reaction region is mostly neutral C( P), but its smaller part consists of C( D) and C( S). reacts with alkanes (e.g., with ethane) as follows. 

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