13C enrichment

The 13C spectrum of normal sterigmatocystin can thus be compared with the spectra of the molecules resulting from separate feeding experiments with 13C enriched (o) 13CH3C02H and (b) CH313C02H, respectively. Those carbon atoms, in each case, which now show enhanced 13C signals can thereby be identified ... 

C- hyperfine satellites are detectable in natural abundance (Figure 3) and their intensities indicate a formulation Cr(C0)4 for the carrier of unpaired spin. Slight anisotropy in the 13C hyperfine structure of the 95 13C- enriched species could only be correctly reproduced in simulations under the assumption of tetrahedral geometry. The centre is thought to be Cr(C0)4+ with a 6At ground state in symmetry, a rare example of a high-spin metal carbonyl. 

The latter mechanism is supported by evidence obtained from the initiation and termination steps in the syndiospecific polymerization of styrene [190]. The 13C-enriched titanium catalyst afforded polystyrene with a CH(Ph)CH213CH3 end group, which indicates that the initiation step proceeded by secondary insertion (2,1-insertion) of styrene into the Ti-13C bond of the active species (Eq. 10). In contrast to this mechanism, termination by the addition of 13C-enriched methanol or tert-butyl alcohol afforded polymers without 13CH30 or tertbutoxy end groups. 

Homologation of 13C-Enriched Acetic Acid CataIyst RuO2-10CH3I... 

Labelling studies with 13C-enriched acetic acid, where 13C NMR data are consistent with carbon monoxide addition to the carbonyl carbon of the acid substrate. 

Bostrom B, Comstedt D, Ekblad A (2008) Can isotopic fractionation during respiration explain the 13C enriched sporocarps of ectomycorrhizal and saprotrophic fungi New Phytol 177 1012-1019 Boutton TW (1996) Stable carbon isotopes ratios of soil organic matter and their use as indicators of vegetation and climate change. In Boutton TW, Yamasaki S (eds) Mass spectrometry of soils. Marcel Dekker Inc., New York, pp 47-82... 

Fig. 2 a, b. EPR and ENDOR spectrum of the low-spin Co(II) Schiff base complex Co(acacen) diluted into a Ni(acacen) 1/2 H20 single crystal, temperature 8K. a) EPR spectrum the two magnetically nonequivalent sites coincide for this particular orientation (EPR observer is marked by an arrow) b) ENDOR spectrum of H, 13C (enriched) and 14N ligand nuclei vp free proton frequency denote the AmN = 2 nitrogen ENDOR transitions. (From Ref. 12)... 

In the ENDOR spectrum (Fig. 2b), however, the resolution is greatly improved so that transitions of the two nitrogens, of four carbons (13C enriched), and of a large number of protons with linewidths between 10 and 50 kHz can be detected. 

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