Carbon origin

In these experiments, the culture medium contained cold (unlabeled) glycine. Because no label was observed at C-2 upon growth in the presence of D-[U-l4C]glucose confirmed that this carbon originated from glycine. 

A small solvent isotope effect was found by Bell and Onwood kuiolkoiO = 1.08) in contradiction to that of only 0.38 reported by Taylor and Halpern . Over one-third of the oxygen present in the carbonate originated from the oxidant when 0-labelled permanganate was used . The reaction is subject to pronounced catalysis by ferric ions . 

The conclusion that the groups neutralized by NaHCOa were in the close vicinity was confirmed by the reaction with ammonia. Here, too, a differentiation between activated and nonactivated oxidized carbons was observed. The amount of ammonia retained after out-gassing at 100° was equivalent to the NaHCOg neutralization with carbons originally not activated. With carbons that had been activated, the ammonia retention was equivalent to only half of this value 35, 46). 

A test tube containing CaCOs is heated until the entire compound decomposes. If the test tube plus calcium carbonate originally weighed 30.08 grams and the loss of mass during the experiment was 4.40 grams, what was the approximate mass of the empty test tube ... 

The reaction involves a [1,3] sigmatropic migration of the carbon originating at C2 with transformation of the three-membered ring C3 C4- C5 to an allylie system. For that reason, the methylenecyclobutane system undergoes thermal automerization. 

The carbon atom of the C02 formed in this reaction is the same carbon originally introduced into malonyl-CoA from HCO3 by the acetyl-CoA carboxylase reaction (Fig. 21-1). Thus C02 is only transiently in covalent linkage during fatty acid biosynthesis it is removed as each two-carbon unit is added. 

Tris(p-tolylphosphine) was used successfully in place of triphenyl-phosphine. The cyanation reaction appears to be a substitutive reaction, the cyano group always occurring on the carbon originally bound to the halogen. 

Table 2. The two failure surfaces are denoted as A and B In the case of the A1TSB and A1TTB pruned samples, the atomic concentration of carbon was about 60% on both sides and is possibly due to carbon originating from partially unreacted alkoxide or residual adhesive. The concentration of oxygen was about 25%. Very little iron was detected on either side, which indicates that Mure did not occur close to the steel substrate. The atomic concentration of sulfur for the A1TSB case is not high enough to conclude that failure occurred primarily within the adhesive. The atomic concentration of aluminum was about 14% on each of the surfaces of both samples. The XPS results support the assignment that failure occurred mainly within the alkoxide layer. The Ti(IV)B primed and TBOSi primed samples also failed mainly within the alkoxide layer.

The target molecule, 2-butanone, contains four carbon atoms. The problem states that all of the carbons originate in acetic acid, which has two carbon atoms. This suggests the following disconnections ... 

Figure 7.39. Schematic diagram illustrating the effects of climate on meteoric diagenetic pathways for coeval carbonates originally composed of a polymineralic assemblage of calcite with various amounts of magnesium and strontium-rich aragonite. (After James and Choquette, 1984.)...

Once the external parameters (pco, p0,- and T) have been established to initiate autonomous kinetic oscillations, these can usually be sustained for periods of time as long as desired, provided that the surfaces are prevented from becoming contaminated (in particular by carbon, originating from spurious traces of hydrocarbons in the feed gas mixture) and that the partial pressures are not drifting off (31). With Pt(l 10) a complication may arise insofar that during the course of the reaction the surface struc-... 

These experiments can be interpreted in two ways, depending on the configuration of citrate. However, in each case, the action of aconitase must be such as to lead to introduction of the double bond of m-aconitic acid between the carbons originally derived from oxaloacetate. This follows from the fact that the carbonyl... 

Fig. 12.8. Simplified sketch showing main relationships inside the coupled calcium and carbon cycles of the oxalate-carbonate pathway in a hypothetical ecosystem. Plants and fungi are oxalate producers. Oxalotrophic bacteria (in the soil or animal guts) use oxalate as carbon, energy and electron sources, leading to CO2 and calcium carbonate production. Calcium carbonate can accumulate inside the soils. Because the carbon of the carbonate originates from organic carbon, its fossilization in the soil constitutes a carbon sink.

It is clear that the detection of carbon originating from CO dissociation requires a method that unambiguously reveals the chemical composition of adlayers ... 

Remember that this carbon originally came from the 0.1156-gram sample of the unknown compound. Thus the mass percent of carbon in this compound is... 

In chemical analytics PCDTs and PCTAs behave very similar to PCDDs and PCDFs. The chromatographic behavior of PCDTs is similar to that of PCDDs. Purification and fractionation with aluminum oxide and activated carbon originally developed for the analysis of PCDDs and PCDFs can be used [28,44]. 

Within the micropores both hydrophilic and hydrophobic pores, of mineral and carbon origin, could be detected. The rieh earbonaeeous materials (gas - coking coal, cellulose) enriched the adsorbents structure in the hydrophobic micropores. 

Mesopores exhibited dual properties of mineral and carbon origin. 

A radical X- also adds to the 7C bond of a carbon-carbon double bond. One electron from the double bond is used to form a new C- X bond, and the other electron remains on the other carbon originally part of the double bond. 

Sea salt aerosol initially consists mainly of seawater (see Table 1). Organic carbon is present in sea salt particles as well, typically enriched in smaller sea salt aerosols compared to bulk seawater carbon (e.g., Blanchard, 1964 Hoffman and Duce, 1977 Blanchard and Woodcock, 1980 Middlebrook et al., 1998 Turekian et al., 2003). This organic carbon originates from three... 

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