Carbon monoxide spectrum

Conclusive evidence that a species of cytochrome P-450 was involved in the hydroxylation was presented by Okuda et al., who showed that the photochemical action spectrum for reversal of the carbon monoxide inhibition of 26-hydroxylation of 5)8-cholestane-3a,7a,12a-triol in rat liver exhibited a maximum at 450 nm [134]. Pedersen et al. [135] and Sato et al. [136] reported simultaneously that small amounts of cytochrome P-450 could be solubilized from the inner membranes of rat liver mitochondria that was active towards cholesterol as well as 5)8-cholestane-3a,7a,12a-triol in the presence of ferredoxin, ferredoxin reductase and NADPH. The mechanism of hydroxylation is thus the same as that operative in the biosynthesis of steroid hormones in the adrenals and in the la-hydroxylation of 25-hydroxyvitamin D in the kidney (Fig. 8). The liver mitochondrial cytochrome P-450 was not active in the presence of microsomal NADPH-cytochrome P-450 reductase [135,136]. Ferredoxin reductase as well as ferredoxin were active regardless of whether they were isolated from rat liver mitochondria or bovine adrenal mitochondria [133]. The partially purified cytochrome P-450 had a carbon monoxide difference spectrum similar to that of microsomal cytochrome P-450 from liver microsomes and adrenal mitochondria. In the work by Pedersen et al. [133], the concentration of mitochondrial cytochrome P-450 in rat liver mitochondria from untreated rats was calculated to be only about 0.1 nmole/mg protein. Treatment of rats with phenobarbital increased the specific content of cytochrome P-450 in the mitochondria more than 2-fold, without significant increase in the 26-hydroxylase activity. The carbon monoxide spectrum of the reduced cytochrome P-450 solubilized from liver mitochondria of phenobarbital-treated rats exhibited a spectral shift of about 2 nm as compared to the corresponding spectrum obtained in analysis of preparations from untreated rats. This was taken as evidence that more than one species of cytochrome P-450 was present in the preparation. It was later shown by Pedersen et al. [137] and Bjbrkhem et al. [138] that the preparation was also able to catalyse 25-hydroxylation of vitamin D3 and that different enzymes are involved in... 

Percent match to saturated carbon monoxide spectrum (%)... 

Whereas ATR spectroscopy is most commonly applied in obtaining infrared absorption spectra of opaque materials, reflection-absorption infrared spectroscopy (RAIRS) is usually used to obtain the absorption spectrum of a thin layer of material adsorbed on an opaque metal surface. An example would be carbon monoxide adsorbed on copper. The metal surface may be either in the form of a film or, of greaf imporfance in fhe sfudy of cafalysfs, one of fhe parficular crysfal faces of fhe mefal. 

Section 6.13.2 and illustrated in Figure 6.5. The possible inaccuracies of the method were made clear and it was stressed that these are reduced by obtaining term values near to the dissociation limit. Whether this can be done depends very much on the relative dispositions of the various potential curves in a particular molecule and whether electronic transitions between them are allowed. How many ground state vibrational term values can be obtained from an emission spectrum is determined by the Franck-Condon principle. If r c r" then progressions in emission are very short and few term values result but if r is very different from r", as in the A U — system of carbon monoxide discussed in Section 7.2.5.4, long progressions are observed in emission and a more accurate value of Dq can be obtained. 

Human-made sources cover a wide spectrum of chemical and physical activities and are the major contributors to urban air pollution. Air pollutants in the United States pour out from over 10 million vehicles, the refuse of over 250 million people, the generation of billions of kilowatts of electricity, and the production of innumerable products demanded by eveiyday living. Hundreds of millions of tons of air pollutants are generated annu ly in the United States alone. The five main classes of pollutants are particulates, sulfur dioxide, nitrogen oxides, volatile organic compounds, and carbon monoxide. Total emissions in the United States are summarized by source categoiy for the year 1993 in Table 25-10. 

Peaks at m/e 113 and 85 have been found in the mass spectra (12) of other O-isopropylidene ketals of sugars, as well as in Figure 7. Since these shift to m/e 119 and to m/e 88 and 91 in the mass spectrum of 10a as they did for the d6-analogs in Reference 12, the structures, 17, 18, and 19 from Reference 12 are shown as possible explanations. The peak at m/e 85 (91) could alternatively be from m/e 113 (119) by loss of carbon monoxide (28 mass units) from the six-membered-ring of structure 17b. 

F.13 Osmium forms a number of molecular compounds with carbon monoxide. One light-vellow compound was analyzed to give the following elemental composition 15.89% C, 21.18% O, and 62.93% Os. (a) What is the empirical formula of this compound (b) From the mass spectrum of the compound, the molecule was determined to have a molar mass of 907 g-mol 1. What is its molecular formula ... 

Korzeniewski C, Pons S, Schmidt PP, Severson MW. 1986. A theoretical analysis of the vibrational spectrum of carbon monoxide on platinum metal electrodes. J Chem Phys 85 4153-4160. 

Adsorbed carbon monoxide on platinum formed at 455 mV in H2S04 presents a thermal desorption spectrum as shown in Fig. 2.4b. As in the case of CO adsorption from the gas phase, the desorption curve for m/e = 28 exhibits two peaks, one near 450 K for the weakly adsorbed CO and the other at 530 K for the strongly adsorbed CO species. The H2 signal remains at the ground level. A slight increase in C02 concentration compared to the blank is observed, which could be due to a surface reaction with ions of the electrolyte. Small amounts of S02 (m/e = 64) are also observed. 

Figure 1. Sketch of the ionization efficiency curves and the "70 eV" mass spectrum for the electron impact ionization of carbon monoxide.

It must be acknowledged, however, that the determination of the number of the different surface species which are formed during an adsorption process is often more difficult by means of calorimetry than by spectroscopic techniques. This may be phrased differently by saying that the resolution of spectra is usually better than the resolution of thermograms. Progress in data correction and analysis should probably improve the calorimetric results in that respect. The complex interactions with surface cations, anions, and defects which occur when carbon monoxide contacts nickel oxide at room temperature are thus revealed by the modifications of the infrared spectrum of the sample (75) but not by the differential heats of the CO-adsorption (76). Any modification of the nickel-oxide surface which alters its defect structure produces, however, a change of its energy spectrum with respect to carbon monoxide that is more clearly shown by heat-flow calorimetry (77) than by IR spectroscopy. 

Before analyzing the results of these, or similar, thermochemical cycles, the assumptions which have been made must be critically examined. Since the cycles are tested for different surface coverages, it is assumed first that the Q-0 curves represent correctly, in all cases, the distribution of reactive sites—the energy spectrum—on the surface of the adsorbent. This point has been discussed in the preceding section (Section VII.A). It is assumed moreover that, for instance, the first doses of carbon monoxide (8 = 0) interact with oxygen species adsorbed on the most reactive surface sites (0 = 0). This assumption, which is certainly not acceptable in all cases, ought to be verified directly. This may be achieved in separate experiments by adsorbing limited amounts of the different reactants in the same se-... 

The role of Os" in the oxidation of various reactants, including hydrocarbons, has been briefly investigated but no definitive data has been obtained. In most of the studies the ESR spectra have been observed following addition of a reactant to a surface which has the superoxide ion. The ESR spectrum of the superoxide ion remains essentially unperturbed upon addition of hydrogen, methane, carbon monoxide or ethylene how-... 

The correlation of the recorded IR spectrum with semiempirical calculations and the reversible cleavage into oxohexapentaenylidene (97) and carbon monoxide give a consistent picture for both, dione 96 and carbene 97. The spectrum of 97 correlates with scaled ab initio vibrational frequencies.123 C60 97 should be a triplet molecule. Indeed, Weltner et al.124 observed during the experiment concerning C4O T-88 another triplet ESR signal which they ascribed to T-97. 

Figure 2. Auger electron spectrum of the surface of two Ru electrodes after deactivation by reduction of carbon monoxide and methanol at higher temperatures (75 and 90 °C respectively in 0.2 M Na2SC>4 at pH 4 and -0.545 V vs SCE ). The presence of K on the surface must result from the adsorption of K+ ions present as an impurity in the electrolyte.

Worked Example 9.9 A spectrum of pipe smoke contains a band at 2180 cm-1, which is attributable to carbon monoxide. What is the force constant k for the C=0 bond ... 

Air/liquid (A/L) interface, adsorption of surfactants at, 24 133-138 Air mass zero (AMO) spectrum, 23 37 Air monitoring, for hydrazine, 13 589 Air oxidized pan, 11 194 Air-path XRF, in fine art examination/ conservation, 11 403—404 Air pollutants. See also Nitrogen oxides (NO j Particulate matter Sulfur oxides (SOJ Volatile organic compounds (VOCs) air toxics, 1 789, 801-802 carbon monoxide, 1 789, 798 common, 26 667 criteria pollutants, l 813t indoor, 1 802-805, 820-823, 821t lead, 1 789, 801... 

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