Carbon difference spectra

Figure Bl.25.4. C Is XPS spectrum of a polymer, illustrating that the C Is binding energy is influenced by the chemical enviromnent of the carbon. The spectrum clearly shows four different kinds of carbon, which corresponds well with the structure of the polymer (courtesy of M W G M Verhoeven, Eindhoven).

Several shifts and coupling eonstants in the NMR speetra set 34 are so typical that the carbon skeleton can be deduced without any additional information. An NOE difference spectrum gives the relative configuration of the eompound. 

Fig. 10. (a) Raman spectra (T = 300 K) of arc-derived carbons from a dc arc cobalt was absent (dotted line) and cobalt was present (solid line) in the carbon anode, (b) the difference spectrum calculated from (a), emphasbjng the contribution from Co-catalyzed nanolubes, the inset to (b) depicts a Lorentzian fit to the first-order spectrum (after ref. [27]). 

Example 2. Vinviidene Chloride Isobutylene Copolymer. The next example is for the carbon-13 spectrum of copolymer vinylidene chloride isobutylene. Figure 5 shows the full spectrum and the peak assignment listing for the non-protonated vinylidene chloride carbon in the 84-92 ppm range. Triad assignments were made (Crowther, M. W., 1987, Syracuse University, unpublished data) using the two-dimensional COLOC (20) experiment. There are ten v-centered pentads representing different environments for the vinylidene chloride carbon. The i represents the non-protonated carbon in the isobutylene polymer unit. 

With T set at V2J, the quaternary carbons generally appear with greater intensity than the other carbons, which will be of near-zero intensities, thereby allowing them to be distinguished, particularly from the CH2 carbons, as compared to the normal APT spectrum, in which both CH2 and quaternary carbons appear with positive amplitudes. A difference APT spectrum, in which an APT spectrum recorded with t set at %/is subtracted from another APT spectrum recorded with t set at /sj, can provide useful information. The methyl carbons will then appear with reduced intensities in the difference spectrum as compared to the methine carbons, allowing us to distinguish between them. 

Figure 39 BC CPMAS NMR spectra of [3- 3C]Ala-labelled ppR (a), A149S (b) and A149V (c) reconstituted in egg PC bilayer. 13CNMR signal at 15.9 ppm corresponding to Alal49 in ppR is shown by the grey (a) and arrows (b, c, and d). The resonance peak at 14.1 ppm is ascribed to methyl carbon peak of egg PC as shown as asterisk. Difference spectrum between (a) and (c) is shown in (d). From Ref. 214 with permission.

An obvious difference was also noted between control and induced skate hepaticdnicrosomal AHH activity in the presence of a-naphthoflavone (10 M). This compound, when added in vitro at this or higher concentrations, caused significant stimulation of AHH activity in control animals (about 3-fold) but inhibition (80%) was found in DBA-pretreated skates. Similar results were earlier reported for control and 3-methylcholanthrene-treated rats (23), where it appears that the response is due to differential effects of a-naphthoflavone on hepatic microsomal cytochrome P-450 (stimulated) and cytochrome P-448 (inhibited) (24). Our data suggests that there may be a novel form of cytochrome P-450 synthesized in skate liver in response to polycyclic hydrocarbon administration, even though there was no hypsochromic shift in the carbon monoxide difference spectrum of dithionite reduced hepatic microsomes from DBA-treated skates (relative to hepatic microsomes from control fish). 

The elution profile of cytochrome P-448 (absorption at 418 nm) and epoxide hydratase activity from a sodium cholate-solubi-lized hepatic microsomal preparation (from DBA-treated male skates) applied to a DEAE-cellulose column and eluted with Buffer II is shown in Fig. 3. The void volume of the column contained significant amounts of epoxide hydratase activity. Fractions 40-70 (Fig. 3) were combined, and concentrated. The carbon monoxide difference spectrum, which had an absorption maximum at 448 nm in the induced state, is shown in Fig. 4. This form of the cytochrome (i.e.,... 

Figure 4. Carbon monoxide difference spectrum of partially purified hepatic microsomal Cytochrome P-448 from DBA-treated little skates. The cuvettes contained dithionite-reduced cytochrome (0.10 mg protein/mL) in lOmM phosphate buffer, pH 7.7, containing 20% glycerol, O.lmM EDTA and O.JtnM dithiothreitol.

The carbon-13 NMR spectrum of acetone oxime has three resonances, the deriva-tized carbonyl carbon at 154.5 ppm and the two nonequivalent CH3 groups at 21.5 and 14.7 ppm. The difference between the chemical shifts of the two methyl groups, 6.8 ppm, is primarily a steric compression shift. This is clearly indicated in the carbon NMR spectrum of methyl ethyl ketoximes (Scheme 1), where the two oxime substituents are not sterically identical and thus the two isomers are not present in equal amounts. In methyl... 

The insensitivity of the DEPT sequence to different JCH coupling constants, as illustrated in Fig. 2.46, makes it useful for editing 13C NMR spectra. To edit a carbon-13 spectrum, three DEPT experiments for the polarization transfer angles... 

Yb(COs)i.o6(OH)o.88 I.7H2O and Lu(COs)i.is(OH)o.74 I.5H2O. The infrared spectrum of La2(COs)3 8H2O differs from those of other normal carbonates with two molecules of water of crystallization. The infrared spectra of the basic carbonates differ from the normal carbonates and may contain OH and MOH vibrations in addition to the water and carbonate absorption bands. 

Fig. 23. (a) Partially relaxed spectrum of the a-methylene carbon at 0 °C, obtained as a tt/2 single pulse sequence with = 0.8 s, and (b) transversally relaxed spectrum for 600 ps and (c) difference spectrum obtained by subtracting (b) from (a). Spectrum (a) represent all noncrystalline contribution and (b) and (c) represent the contributions of the amorphous and crystalline-amorphous interphases, respectively... 

Figure 8. Carbon, Cls, spectra. Key a, from a polyvinyl alcohol homopolymer reference sample b, a spectrum of a modified glassy carbon surface corresponding to Fig. 7, spectrum e and c, the difference spectrum obtained by subtracting b from a, magnified 2X- (Reproduced, with permission, from Ref. 22. Copyright 1981, Pergamon Press.)...

The difference spectrum shows negative absorbance at 1720 cm"1 which is due to the reaction between -COOH groups on the oxidised carbon black surface and to -NH2+— and Si-OCH3 of silane coupling agent. This is further substantiated from the appearance of a peak at 1635 cm-1 with a shoulder at 1620 cm 1, which is due to formation of -(C=0)—N—(amide) and -Si-0-(C=0)- (silyl ester). 

Here, T is the observed line width (Av << F), 7d is the peak-to-valley intensity in the difference spectrum, and To is the peak height of the Raman line. Although this equation is for Lorentzian-shaped bands, the results are approximately the same for Gaussian-shaped bands (the constant 0.385 becomes 0.350). In the case of carbon disulfide-benzene mixtures, the smallest shift observed was -0.06 cm-1, and the associated error was 0.02 cm-1 (77). A convenient rotating system that can be used for (1) difference spectroscopy, (2) normal rotating sample techniques (solid and solution), and (3) automatic scanning of the depolarization ratios as a function of the wave number has been designed (45). 

Fig. 18.10. In situ FT1R difference spectrum collected at +400 mV vs. RHE during an experiment in which the potential of the platinum particulate electrode (dispersed on carbon), which is initially immersed in 1.0 M H2S04, is first fixed at +50 mV vs. RHE. 1.0M CH3OH is then added to the electrolyte, and the potential was increased from +50 mV vs. RHE in successive 50 mV steps to 400 mV. All the spectra (8 cm-1 resolution, 100 coadded averaged scans requiring ca. 60 scans per second) were normalised to the reference spectrum taken at the base potential of 50 mV.

The common feature of all black carbon constituents is the strong absorption within the whole solar spectrum. Black carbon particles are particularly toxic as pollutants on the other hand, they share the beneficial aspect of shielding efficiently harmful UV radiation. Although commercial products such as industrially produced carbon black, impure graphite and activated carbon differ chemically and morphologically from emitted organic aerosols, they are usually used as model particles for screening studies [56]. So far,... 

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