Carbon results

Ma.nufa.cture. Several nickel oxides are manufactured commercially. A sintered form of green nickel oxide is made by smelting a purified nickel matte at 1000°C (30) a powder form is made by the desulfurization of nickel matte. Black nickel oxide is made by the calcination of nickel carbonate at 600°C (31). The carbonate results from an extraction process whereby pure nickel metal powder is oxidized with air in the presence of ammonia (qv) and carbon dioxide (qv) to hexaamminenickel(TT) carbonate [67806-76-2], [Ni(NH3)3]C03 (32). Nickel oxides also ate made by the calcination of nickel carbonate or nickel nitrate that were made from a pure form of nickel. A high purity, green nickel oxide is made by firing a mixture of nickel powder and water in air (25). 

The acidic character of siUca is shown by its reaction with a large number of basic oxides to form siUcates. The phase relations of numerous oxide systems involving siUca have been summarized (23). Reactions of siUca at elevated temperatures with alkaU and alkaline-earth carbonates result in the displacement of the more volatile acid, CO2, and the formation of the corresponding siUcates. Similar reactions occur with a number of nitrates and sulfates. Sihca at high temperature in the presence of sulfides gives thiosiUcates or siUcon disulfide, SiS2. 

Cychc carbonates result from polyols by transesterification using organic carbonates (115). Thus sorbitol and diphenylcarbonate in the presence of dibutyl tin oxide at 140—150°C form sorbitol tricarbonate in quantitative yield (116). 

Carbon Composites. Cermet friction materials tend to be heavy, thus making the brake system less energy-efficient. Compared with cermets, carbon (or graphite) is a thermally stable material of low density and reasonably high specific heat. A combination of these properties makes carbon attractive as a brake material and several companies are manufacturing carbon fiber—reinforced carbon-matrix composites, which ate used primarily for aircraft brakes and race cats (16). Carbon composites usually consist of three types of carbon carbon in the fibrous form (see Carbon fibers), carbon resulting from the controlled pyrolysis of the resin (usually phenoHc-based), and carbon from chemical vapor deposition (CVD) filling the pores (16). 

Chemical Properties. Neopentanoic acid [75-98-9] undergoes reactions typical of carboxyUc acids. Reactions often proceed less readily than with straight-chain acids because of the steric hindrance around the carbonyl group. However, this steric hindrance at the a-carbon results ia derivatives that are typically more resistant to hydrolysis and oxidation. 

The reaction of a-bromoenone (307) with hydroxylamine hydrochloride in ethanol in the presence of potassium carbonate resulted in the regiospecific formation of 3-alkyl-5-phenylisoxazoles (303). On the other hand, when sodium ethoxide was used as the base under similar conditions, 5-alkyl-3-phenylisoxazoles (308) were obtained exclusively (80CC826, 81H(16)145). 

Steel in cement mortar is in the passive state represented by field II in Fig. 2-2. In this state reinforcing steel can act as a foreign cathodic object whose intensity depends on aeration (see Section 4.3). The passivity can be lost by introduction of sufficient chloride ions or by reaction of the mortar with COj-forming carbonates, resulting in a considerable lowering of the pH. The coordinates then lie in field I. The concentration of OH ions can be raised by strong cathodic polarization and the potential lowered, resulting in possible corrosion in field IV (see Section 2.4). 

The checkers performed this step on a smaller scale (ca. f) and noted (proton magnetic resonance spectrum) occasional contamination (up to 10%) by phthalic anhydride. This impurity causes no subsequent difiSculties. Washing of the crude reaction mixture with cold aqueous sodium hydrogen carbonate resulted in serious product loss because of its appreciable solubility in this medium and therefore should be avoided. 

Mcntasty el al. [35] and others [13, 36] have measured methane uptakes on zeolites. These materials, such as the 4A, 5A and 13X zeolites, have methane uptakes which are lower than would be predicted using the above relationship. This suggests that either the zeolite cavity is more attractive to 77 K nitrogen than a carbon pore, or methane at 298 K, 3.4 MPa, is attracted more to a carbon pore than a zeolite. The latter proposition is supported by the modeling of Cracknel et al. [37, 38], who show that methane densities in silica cavities will be lower than for the equivalent size parallel slit shaped pore of their model carbon. Results reported by Ventura [39] for silica xerogels lead to a similar conclusion. Thus, porous silica adsorbents with equivalent nitrogen derived micropore volumes to carbons adsorb and deliver less methane. For delivery of 150 V./V a silica based adsorbent would requne a micropore volume in excess of 0.70 ml per ml of packed vessel volume. 

When dimethyl 3-benzoxepin-2,4-dicarboxylate is reacted under controlled conditions (15 min) with hydrogen it is possible to isolate dimethyl l,2-dihydro-3-benzoxepin-2,4-dicarboxylate.17 Hydrogenation of 2-nitrodibenz[, /]oxepin-10-carboxylic acid in the presence of palladium on potassium carbonate results in the reduction of the nonaromatic C C double bond and the nitro group to give 2-amino-10,l l-dihydrodibenz[i,/]oxepin-10-carboxylic acid.107... 

Successive treatment of the diazepinone 8 with triethyloxonium tetrafluoroborate and sodium hydrogen carbonate results in ethyl 5-ethoxy-l/f-l,4-diazepine-l-carboxylate (9).31... 

Kinetic stability of lithium and the lithiated carbons results from film formation which yields protective layers on lithium or on the surfaces of carbonaceous materials, able to conduct lithium ions and to prevent the electrolyte from continuously being reduced film formation at the Li/PC interphase by the reductive decomposition of PC or EC/DMC yielding alkyl-carbonates passivates lithium, in contrast to the situation with DEC where lithium is dissolved to form lithium ethylcarbonate [149]. EMC is superior to DMC as a single solvent, due to better surface film properties at the carbon electrode [151]. However, the quality of films can be increased further by using the mixed solvent EMC/EC, in contrast to the recently proposed solvent methyl propyl carbonate (MPC) which may be used as a single sol-... 

Above C4, aliphatic aldehydes undergo the McLafferty rearrangement, resulting in an observed m/z 44 ion, provided the a-carbon is not substituted. Substitution on the a-carbon results in a higher m/z peak. (See the proceeding text.)... 

Regardless of the scale used, silicon always appears markedly more electropositive than carbon, resulting in polarization of silicon-carbon bonds in the sense Si4+—C1-, and for nucleophilic attack to occur at silicon. 

Although at first glance addition to the central carbon and formation of what seems like an allylic carbonium ion would clearly be preferred over terminal addition and a vinyl cation, a closer examination shows this not to be the case. Since the two double bonds in allenes are perpendicular to each other, addition of an electrophile to the central carbon results in an empty p orbital, which is perpendicular to the remaining rr system and hence not resonance stabilized (and probably inductively destabilized) until a 90° rotation occurs around the newly formed single bond. Hence, allylic stabilization may not be significant in the transition state. In fact, electrophilic additions to allene itself occur without exception at the terminal carbon (54). 

Buesseler KO, Bauer JE, Chen RF, Eglinton TI, Gustafsson O, Landing W, Mopper K, Moran SB, Santschi PH, Vernon Clark R, Wells ML (1996) An intercomparison of cross-flow filtration techniques used for sampling marine colloids overview and organic carbon results. Marine Chem 55 1-31 Buffle J, Perret D, Newman M (1992) The use of filtration and ultrafiltration for size fractionation of aquatic particles, colloids, and macromolecules. In Enviroiunental particles. Buffle J, van Leeuwen HP (eds) Lewis Publishers, Boca Raton FL, pl71-230... 

Kikuchi et al. have observed that the initial attack of amine occurs at the carbonyl carbon, resulting in the formation of an ionic intermediate 26. This reaction is very sensitive to the solvent polarity. Under nitrogen atmosphere, intermediate 27 is further aminated to give 28. Oxidation of 27 and 28 gives 23 and 24, respectively. Oxidation in nitrobenzene, however, results in dealkylation products. In the presence of air and triethylamine, decomposition of aminoanthraquinones occurs. 

The reaction of malonates 213 with 2equiv of an amidoxime in the presence of potassium carbonate results in the formation of the bis-l,2,4-oxadiazoles 214 (Equation 35), a process that also gives excellent yields of the mono-1,2,4-oxadiazoles when a 1 1 ratio is employed (see Table 5) <2006TL3629>. 

The propensity of S-S dications to undergo dealkylation was found to decrease in the order of methyl > ethyl > benzyl. This order of reactivity parallels the increase in the stability of the corresponding carbocations.94 Dealkylation of dication 77 affords thiosulfonium salt 78 in quantitative yield.95 Kinetic studies suggest SN1 mechanism of dealkylation. In addition, reaction of sulfoxide 79 with a substituent chiral at the a-carbon results in racemic amide 80 after hydrolysis. 

Williams [81,84] found that a high-energy ultraviolet oxidation method gave dissolved organic carbon results for seawater samples that were higher than those obtained by the wet persulfate oxidation method described by Menzel and Vaccaro [46]. Other variations on the method have been published. 

For those who are concerned with the preparation of samples for the direct 14C counting systems, this summary vividly illustrates the effects on the final age value as a result of the addition of ppm levels of modern carbon for samples in different age ranges. For a sample with an actual age of 75,000 years, for example, a 100 ppm addition of modern carbon results in approximately a 5000-year error in the final measured age. Hopefully, contamination of a sample with modern carbon would be a relatively rare occurrence. A more probable situation would involve the addition of carbon differing in age from the original samples from several hundred up to several tens of thousands of years. 

Oxygen is more electronegative than carbon, resulting in polar bonding. Because there are no unshared pairs of electrons for carbon, a linear molecule results. 

Although oxidation potentials of aldehydes and ketones are generally very high, silyl substitution at the carbonyl carbon results in a significant decrease in the oxidation potential [16]. The decrease in the oxidation potentials is attributed to the rise of the HOMO level by the interaction of the C Si cr-bond and the nonbonding p orbital (lone pair) of the carbonyl oxygen (Fig. 9). In the case of a-silyl-substituted ethers, the rotation around the C-O bond is free and,... 

The nucleophilic attack on the bridging carbon results in two different reactivities. Usually ring opening occurs. Malononitrile under hydrolytic solid-liquid phase-transfer conditions attacks the methiodides 26 at the fusion carbon atom, thereby inducing ring opening and the formation of 4-(Ar-aryl-3 -methylisothioureido)-5-(dicyanomethylcnc)-l-... 

Preparation of 2-unsubstituted products by this method would require the use of formaldehyde as the aldehyde component, which gives low yields. However, the use of glyoxylic acid, either as the free acid or bound to macroporous polystyrene carbonate, results in satisfactory formation of the 2-unsubstituted products through an in situ decarboxylation <2004OL4989>. The use of a nonpolar solvent (toluene) has been reported to reduce the formation of side products in this type of reaction <2006TL947>. 

Alternately, the weight lost when the carbonate is reacted with HC1 can be determined. Heating carbonates results in their decomposition. Thus, soils containing carbonate can be heated to the appropriate temperature and the loss of weight measured. In this approach, the loss of organic matter and water of hydration of various components in soil must be accounted for in order to determine the weight of carbon dioxide [7],... 

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