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NMR chemical shift values

NMR Chemical Shift Values" of the Ring Carbons OF Representative 1,2-Dithietes... [Pg.272]

Purcell and coworkers obtained good correlations between the IR and H NMR methods by the use of 1,1,1,3,3,3-hexafluoropropanol and phenol as acids . Taddei and colleagues have reported that with CHCI3 as the donor, a free energy relationship is established between the association constants and the H NMR chemical shift values of CHCI3 in the presence of Lewis bases. However, a non-linear relationship has been observed for several other Lewis bases and CHCI3 by other authors . [Pg.552]

The behaviour of the mutant enzymes where, for example, histidine-152 has been changed to alanine is compared with that of wild type enzymes.60 The 31P NMR chemical shift values and signal width for H152A mutant enzyme have shown the presence of two conformers open and closed forms of the enzyme that interconvert slowly on the NMR time scale. The tightness of the binding of the cofactor to the protein surface and its protonation state have been also discussed for intermediate Schiff bases in different steps of the catalytic cycle (Table 1). [Pg.155]

The reported, 29Xe NMR chemical shifts. Values in italic were referenced to XeF2 in MeCN as primary standard. h The, 29Xe NMR chemical shifts were referenced to XeOF4 (24 °C) and extrapolated to -30 °C if measured at other temperature (53). c, 3C NMR 6 81.2 (d, 2J(C-2,Xe) = 69 Hz, C-2). [Pg.458]

SCHEME 2. nO NMR chemical shift values (ppm) in CDCI3 solution for compounds 18-34... [Pg.80]

TABLE 13. 13C NMR chemical shift values of conjugated linoleic acid isomers... [Pg.82]

TABLE 30. 13C NMR chemical shift values (8), spin-lattice relaxation times (T ) and nuclear Overhauser effects (NOE) for /1-carotene (78) in CDCI3 at various magnetic field strengths ... [Pg.132]

TABLE 31. I3C NMR chemical shift values (5), observed and calculated spin-lattice relaxation times (7i ) and observed nuclear Overhauser effects (NOE) for zinc me.vo-tetrapheny I porphyri n (79) in CDCI3 solution at 9.4 T... [Pg.133]

The H NMR spectram (CDClj, 500 MHz) of 12 showed two singlets (8 0.83 and 8 0.95), each integrating for three protons due to the C-18 and C-19 methyl protons. Three 3H doublets at 8 0.78 (J= 6.5 Hz), 8 0.79 (J= 6.5 Hz) and 8 0.85 (J = 7.0 Hz) were due to the secondary C-26, C-27 and C-21 methyl protons, respechvely. The C-3 methine proton resonated as a one-proton double doublet at 8 3.63 (JJ= 10.5 Hz and J2= 3.5 Hz) and its downfield chemical shift value was indicative of the presence of a geminal hydroxyl funchonality. A one-proton mulhplet at 8 5.21 was ascribed to the C-6 olefinic proton. The C-28 exocyclic methylene protons appeared as two broad singlets at 8 5.40 and 5.58. The C-NMR spectram (CDCl, 125 MHz) showed the resonance of all 28 carbon atoms. The combination of H and C-NMR data suggested that compound 12 has a sterol like structure as most of the H and C-NMR chemical shift values of 12 were similar to those of sterols reported in the literature [19, 20]. The H and C-NMR chemical shift values were assigned with the aid of COSY-45 , HSQC and HMBC spectral data. Compound 12 was found to have modest inhibitory activity against C. xerosis and S. aureus with minimal inhibitory concentration values of 82.35 and 146 pg/ml, respectively. [Pg.61]

Typical NMR Chemical Shift Values of Acyl Moieties of Acylated Flavonoid Glycosides Recorded in DMSO-c/6 (D) or CD3OD (M) with Various Proportions of CF3COOD (T) or Acetone (A)... [Pg.69]

Olah et al.532,533 studied trihalomethyl cations (CX3+, X = Cl, Br, I) under stable ion conditions. 13C NMR chemical shift values correlate well with the decreasing order of back-donation (Cl > Br > I). Similar correlation was also found for dimethylhalo-carbenium ions 258. The CF3+ fluoro analog, however, could not be observed under any conditions. This can be attributed to a combination of unfavorable thermodynamics (generation of CF3+ from CF4 is endothermic by about 20lstarting materials and a suitably strong Lewis acid.534... [Pg.170]

Table 6.3 H NMR chemical shift values" of reference compounds A-C, and compounds 1-11 identified in a leachate from an industrial landfill site. Reprinted from Benfenati, E., Pierucci, P., Fanelli, R., Preiss, A., Godejohann, M., Astratov, M., Levson, K. and Barcelo, D.,c. /. Chromatogr., A, 831, 243-256, copyright (1999) with permission of Elsevier Science. Table 6.3 H NMR chemical shift values" of reference compounds A-C, and compounds 1-11 identified in a leachate from an industrial landfill site. Reprinted from Benfenati, E., Pierucci, P., Fanelli, R., Preiss, A., Godejohann, M., Astratov, M., Levson, K. and Barcelo, D.,c. /. Chromatogr., A, 831, 243-256, copyright (1999) with permission of Elsevier Science.
Figure 7. Protonated dimethylsulfoxide (DMSO) and calculated 13C NMR chemical shift values. Figure 7. Protonated dimethylsulfoxide (DMSO) and calculated 13C NMR chemical shift values.
The alkylation on the P atom of substituted phosphinines resulted in anionic /.4-phosphinines [315], The aromaticity of the ring is significantly reduced according to NMR chemical shift values. Similarly, the adduct of triphosphabenzene with ethyl-magnesium-bromide has been reported to yield an ion pair, which resulted in a nonplanar structure with nonequalized bond lengths [316],... [Pg.73]

Figure 1 11B NMR chemical shift values for typical boronates. Figure 1 11B NMR chemical shift values for typical boronates.
Monocyclic Phosphoranoxide Anion. The lp NMR chemical shift value and line width of 10 is solvent and pH sensitive, suggesting the equilibria shown in Scheme III. The structure of 11 is confirmed by preparation and characterization of the analogous stable BF4 salt. Deprotonation of 10 by NaH in THF is much faster than that of its para isomer. This deprotonation is followed by broadening, gradual upfield shift and resharpening of the NMR signal from 38.5 to -31.0 ppm. The latter, somewhat broad line is consistent with structure 14 in equilibrium with a small concentration of 13. [Pg.437]


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