L,C-NMR spectrum

Four different experiments were realized by labeling either the methanol or the ethylene molecules (Figure 7). The reactions were studied in static conditions adsorbing either methanol (A and B) or ethylene (C and D) prior to the second reactants. The l C-NMR spectra of Figure 7 reveals that the order of adsorption of the reactants is very important for the reactivities at first, surface alkylation occurs and is followed by separated reaction pathways for CH3OH and C2H/. 

Several internal olefins were also tried in the reaction shown in eq 1. When the reaction of both cis-or trans-2-butene were run at 230°C, they gave a low (10%) yield of the. 2,3-bis (dichlorophosphino)butane as evidenced by a single 31p nmr peak at 193.6 ppm and a symmetrical l C-NMR spectra. When the reaction temperature is raised to 250°C, both cis-and trans-2-butene yield a compound which has the same 31p and 13c-NMR spectra as 6, indicating a l,2-bis(dichlorophosphino)butane product. Along with this rather complex isomer product change, there is an increase in the amount of butylphosphonous dichloride formed. 

Figure 9.36. l C nmr spectra of ethyl phenylacetate (from J. A. Moore and D. L. Dalrympk, Experimental Methods im Organic Chemistry, W. B. Saunders Co., 1976)... 

Interprefatio/i gf l C-NMR spectra - the spectrum is that"Of all the carbon atoms in the molecule.Jt is easy to forgetjthatiT "the peaks fpr carbon atoms carrying no" hydrogen atwris are pjesent." ... 

General Information. The and l c NMR spectra were recorded at 400 MHz and 100 MHz, respectively, with a Varian XL-400 spectrometer on solutions of the compounds in DCCI3 and with TMS as the internal standard. All NMR spectra were obtained with proton decoupling as were the P NMR spectra which were recorded at 161.9 MHz (referenced to external 85% H3PO4). Chemical shifts downfield from the reference are positive and upfield are negative. Some early NMR experiments were done at 300 MHz. All experiments were performed under N2. Off-resonance experiments confirmed the carbon signals. 

Table III. Chemical Assignments of Resonances in the CPMAS-l C-NMR-Spectra of Insect Cuticles3...

Figure 1. l,C NMR spectra of tetraethylene glycol (lower) and its divinyl ether (upper) taken on neat samples. 

A review of the occurrence in nature and production of solasodine is available [632]. The completely assigned and l C NMR spectra of 281 have been reported [633]. 

Figure 13.3 shows both the lH and the l C NMR spectra of methyl acetate, CH3C02CH3. The horizontal axis shows the effective field strength felt by the nuclei, and the vertical axis indicates intensity of absorption of rf energy. Each peak in the NMR spectrum corresponds to a chemically distinct nucleus in the molecule. [Note that NMR spectra are formatted with the zero absorption line at the bottom, whereas IR spectra are formatted with the zero absorption line <100% transmittance) at the top Section 12.5.] Note also that H and 13C spectra can t both be observed at the same time on the same spectrometer because different amounts of energy are required to spin-flip the different kinds of nuclei. The two spectra must be recorded separately. 

A new alkaloid (7) is the first example of a Gelsemium alkaloid having an A a-methoxyindole moiety in the molecule. This alkaloid may be an early biogenetic intermediate to the A a-methoxyoxindole alkaloids and their related compounds. Full assignments of the IH- and l C-NMR spectra of A7 a-methoxy-19(Z)-anhydrovobasinediol (7) were conducted mainly by CSCM ID (decoupled selective population transfer experiment) (18) and selective INEPT (insensitive nuclei enhanced by polarization tansfer) (19) experiments. The structure was finally determined by single crystal X-ray analysis (11). 

Figure lb. CP/MAS-l- C-NMR-spectra of viscose staple fibre after various treatments. 

The solid-state l C-NMR spectra of the fibrous hydrocellulose also demonstrate the predominance of the cellulose I allomorph (Figure 6). All three spectra contain the sharp resonances associated with the cellulose I conformation and the broader C-4 and C-6 resonances indicative of regions of three-dimensional disorder and crystallite surfaces (16,17). The relative intensities of the sharp and broad resonances of the three spectra are similar, again demonstrating the lack of change in physical structure during degradation. 

Methyl- or k-Methylpentadiene The resulting polymers obtained from both monomers are rubbery and soluble in CCI4, CHCI3 and so on. Figure 2(d) and 2(e) show the l C-NMR spectra of the polymers. In both spectra strong six absorption peaks are observed, which indicates that the polymers contain more than 99% of head-to-tail, 1,4-trans structure. 

The "E spectral region was not used in the above analyses because phasing difficulties led to consistently high results. This will be a typical problem in l C NMR spectra where there is a strong dominant resonance close to substantially weaker resonances of interest. 

On the experimental side, just like vibrational spectra, l C-NMR spectra may be used to distinguish the two groups of metal carbonyls. The chemical shifts of classical transition-metal carbonyls range from 190 to -215 ppm (83), while for [Au(13cO)2]+ [Au(13cO)]+, and [Pt(CO)4]2+ shifts of 174,162 and 130 ppm have... 

When Zr-COOH-OH was treated with hexylamine directly, the product showed four orders of ((X)/) reflections in the powder XRD pattern from a 26.2 A phase. This compares to a interlayer spacing of 28.7 A for the hexylammonium intercalate of Zr(03PCH2CH2C00H)2. Curiously, both the IR and l C NMR spectra of this product suggest that a small amount amide was formed in addition to the expected hexylammonium product. 

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