Sulfur , exchangeability with carbon

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. 

A flow diagram for the system is shown in Figure 5. Feed gas is dried, and ammonia and sulfur compounds are removed to prevent the irreversible buildup of insoluble salts in the system. Water and soHds formed by trace ammonia and sulfur compounds are removed in the solvent maintenance section (96). The pretreated carbon monoxide feed gas enters the absorber where it is selectively absorbed by a countercurrent flow of solvent to form a carbon monoxide complex with the active copper salt. The carbon monoxide-rich solution flows from the bottom of the absorber to a flash vessel where physically absorbed gas species such as hydrogen, nitrogen, and methane are removed. The solution is then sent to the stripper where the carbon monoxide is released from the complex by heating and pressure reduction to about 0.15 MPa (1.5 atm). The solvent is stripped of residual carbon monoxide, heat-exchanged with the stripper feed, and pumped to the top of the absorber to complete the cycle. 

Lithiation of dibenzofuran with butyllithium and mercuration both occur at the 4-position. Thallation occurs at the 2-position, however (57IZV1391). The mercury and thallium derivatives serve as a source of the iodo compounds by reaction with iodine. Bromodibenzofurans undergo bromine/lithium exchange with butyllithium and the derived lithio compounds may be converted into phenols by reaction with molecular oxygen in the presence of a Grignard reagent, into amines by reaction with O-methylhydroxylamine, into sulfinic acids by reaction with sulfur dioxide, into carboxylic acids by reaction with carbon dioxide and into methyl derivatives by reaction with methyl sulfate (Scheme 100). This last reaction... 

The leaching reactions and the distribution of the various anionic uranyl species are very dependent on the pH value of the leach liquor and on the sulfate or carbonate concentration. Nominally, only the anionic di- and tri-sulfate or carbonate species will exchange with the functional groups of an anion-exchange resin, but the resin itself can facilitate the formation of complex anions in the resin phase because of the high concentration (approximately 0.5 M) of the co-ion on the functional group. Therefore, a complex equilibrium is established in which the resin is a participant the following reactions describe these equilibria for sulfuric acid leach liquors ... 

The imines (CFa)2C=NH and (CFa)2S=NH are convincing examples for this carbon-sulfur exchangeability. Reactions of the two imines with RLi, RC1, C1F, as well as photolysis, hydrolysis, and their preparation are similar and take place according to Table I. 

Oxygen-sulfur heteroatom exchange has been achieved with 3-methyl-benzene thiazole-2-thione in the presence of trifluoroacetic acid and with l-phenyl-5-mercaptotetrazole. Thiirane can be prepared from oxirane on a support impregnated with alkali metal salts, by decomposition of the dithiocarbon-ate formed with carbon disulfide. A macrocyclic ether, perhydrobenzo-18-crown-6, plays a role in the nucleophilic reaction of oxirane with KCNS, which leads to thiirane in good yield. ... 

Deuterium does not give a signal under the conditions of NMR spectroscopy. Thus, replacement of a hydroxyl proton by deuterium leads to the disappearance of the OH peak. Protons bonded to nitrogen and sulfur also undergo exchange with D2O. Those bound to carbon normally do not, and so this technique is useful for assigning the proton resonances of OH, NH, and SH groups. 

Tracer studies with l4C and 35S also provided information about the mechanism of the overall reaction given by Eq. (23) (233). Experiments employing reaction mixtures containing all four species or only carbon or sulfur compounds, with steam as a diluent, were carried out with labeled l4C02 and 35S. It was possible to measure the reverse l4C transfer when sulfur compounds were removed from the reaction chamber. Thus the exchange reaction... 

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