Nitrogen, Carbon, and Sulfur

The oxidation-reduction reactions of C, N, S, and O in soils are, virtually without exception, catalyzed by microbial enzymes. These reaction rates without such catalysis are very slow (irreversible). Even with catalysis, the reactions are quite irreversible. The behavior of carbon and nitrogen in particular is dominated by nonequilibrium. 

Although many microorganisms are apparently capable of denitrification, only a few specialized species, including the free-living Azotobacter, blue-green algae, some anaerobic bacteria, and Rhizobium bacteria in root nodules of legumes, are ca- 

High NOJ concentrations in groundwaters generally result from the following  

High organic matter inputs to soils, including waste disposal operations. Sewage sludge, manure disposal, and irrigation with wastewaters can load 

The complete mechanism of soil nitrogen redox changes is unknown despi te much study. The overall oxidative reactions are 

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The extent of gas-to-aerosol conversion of secondary pollutants can be estimated by measuring gas particle distribution factors for carbon, nitrogen, and sulfur species. For example, /c = P/ P + G), where P = particulate organic carbon ng/m as carbon) and G = gas-phase... 

Sakai H, Casadevall TJ, Moore JG (1982) Chemistry and isotope ratios of sulfur in basalts and volcanic gases at Kilauea volcano, Hawaii. Geochim Cosmochim Acta 46 729-738 Sakai H, DesMarais DJ, Ueda A, Moore JG (1984) Concentrations and isotope ratios of carbon, nitrogen and sulfur in ocean-floor basalts. Geochim Cosmochim Acta 48 2433-2441 Sano Y, Marty B (1995) Origin of carbon in fumaroUc gas from island arcs. Chem Geol 119 265-274... 

As previously noted, no electrophilic attack at ring carbon, nitrogen, and sulfur has been reported with the exception of a sulfonium ylide intermediate formed from reaction of l,3,4-oxathiazole-2-ones with a carbene, which will be discussed later (see Section 4.14.5.5). 

Macias, E.S. Radcliff, C.D. Lewis, C.W. Sawaki, C.R., Proton-Induced y-ray Analysis of Atmospheric Aerosols for Carbon, Nitrogen, and Sulfur Composition, Anal. Chem., 1978, 5, 1120. 

Reactions with carbon, nitrogen and sulfur nucleophiles 214 Direct observation of nitrenium ions acid-base chemistry and singlet-triplet chemistry 227 Heteroarylnitrenium ions 238 Calculations 244... 

REACTIONS WITH CARBON. NITROGEN AND SULFUR NUCLEOPHILES... 

Our understanding of the chemistry of N-arylnitrenium ions is significantly more advanced than it was a decade ago. Nevertheless, this field of research is still considerably less developed than that of carbenium ions, carbenes, or nitrenes. For example, although singlet nitrenium ions behave as one might expect that their 4-imino-2,5-cyclohexadienyl resonance contributors would in their reactions with H2O, NJ, or Cl, their reactions with carbon, nitrogen, and sulfur nucleophiles, particularly d-G, are not so easily rationalized. Except for d-G, these reactions with soft nucleophiles have not been examined systematically and the regiochemistry exhibited by these nucleophiles is incompletely understood. 

J. Greyson, Carbon, Nitrogen and Sulfur Pollutants and Their Determination in Air and Water, Marcel Dekker, Inc., New York, 1990. 

When dealing with transformation reactions, it is important to know whether electrons have been transferred between the reactants. For evaluating the number of electrons transferred, it is convenient to examine the (formal) oxidation states of all atoms involved in the reaction. Of particular interest to us will be the oxidation state of carbon, nitrogen, and sulfur in a given organic molecule, since these are the elements most frequently involved in organic redox reactions. 

Equipment and Procedure. Figure 1 is a diagram of the continuous, 2%-in. id fluidized bed combustion unit that was used. The melt is fed via syringe feeders and is dropped from a remote drip tip into a batch bed of fluidized solids that is fluidized by feed air that enters at the apex of the reactor cone. The carbon, nitrogen, and sulfur are burned out in the fluidized bed, and the zinc chloride is vaporized. The gas, zinc chloride vapor, and elutriated solids leaving the reactor pass through the cyclone where the solids are collected. The cyclone underflow solids... 

Table VI gives the distribution of carbon, sulfur, and nitrogen in the products for runs at 983°C and 1038°C. One-hundred fifteen percent of stoichiometric air was used in both runs. The feed gas was pure air. It is apparent that the carbon, nitrogen, and sulfur impurities were almost completely burned out, i.e., 89% or more burn-out was achieved. The effluent melt contained less than 3% of the carbon and sulfur in the feed melt and 11% or less of the nitrogen.

Step 5. If no unassigned electrons remain after step 3 but the central atom does not yet have an octet, use one or more lone pairs of electrons from a neighboring atom to form a multiple bond (either double or triple). Oxygen, carbon, nitrogen, and sulfur often form multiple bonds. Worked Example 7.7 shows how to deal with such a case. 

Carbon-, nitrogen-, and sulfur-containing species account for most of the mass of aerosol particles. In spite of years of effort by many investigators, the exact chemical forms of carbon, sulfur, and nitrogen in these particles are not known nor are the formation mechanisms of these species known with certainty. There are many reasons for this situation, including the complexity of the system and the dependence of the apparent chemical composition on the analytical methods used. For example, wet chemical analyses of sulfur and nitrogen species report only ions in solution. These ions, however, may be originally water soluble (e.g., sulfate and ammonium from ammonium sulfate), or they may be ionic products of hydrolyzable species such as amides (1). Of course, insoluble species will not be detected by wet chemical techniques. 

Electrophilic Attack at Ring Carbon, Nitrogen, and Sulfur 124... 

As previously noted, no electrophilic attack at ring carbon, nitrogen, and sulfur has been reported. 

Among the four elemental components, carbon, nitrogen, and sulfur represent natural chemical redox couples, because each element occurs both in an oxidized and a reduced state. The process of formation of organic matter by photosynthesis constitutes chemical reduction of C, N, and S from their inorganic... 

The reaction of C 4-acetoxylated catechin 517 and epicatechin with nucleophiles under Lewis acid conditions to yield C-4-elaborated flavan-3-ols 518 has been described. The C 4 acetoxy group is activated by a Lewis acid, such as BFj-OEo or TMSOTf, allowing delivery of a variety of carbon-, nitrogen-, and sulfur-based nucleophiles in stereoselective fashion to this position (Scheme 94) <2002TL7753>. An SnI mechanism was invoked for the process. Table 4 displays the results for catechins. 

There are >40 distinct molybdenum enzymes that occur in all classes of living systems and are especially important in the biochemical cycles of carbon, nitrogen, and sulfur (24b). The majority of the molybdenum enzymes, with notable exceptions including the nitrogenases (25-28) and a 2-hydroxyglutaryl-CoA dehydratase (10), catalyze a conversion of the type [Eq. 1], that is, the net effect of the catalysis corresponds to the transfer of an oxygen atom to or from the substrate. 

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