Proton decoupling, NMR

Figure 4.31 75 MHz proton-decoupled NMR spectrum of nitroethane, CH3CH2NO2, and DEPT 135 spectrum (/nsef) in CDCI3...

A compound CeHsFO has a broad peak in the infrared at about 3100-3400 and the following signals in its (proton decoupled) NMR spectrum. Suggest a structure for the compound and interpret the spectra. 

Figure 6. Proton-decoupled NMR spectrum at 20,000 MHz in THF-dg of the THF-soluble, pentane-insoluble products of a 2-hr reaction of subbituminous coal in tetralin...

Figure 7. Aromatic regions of proton-decoupled NMR spectra of THF-soluble, pentane-insoluble reaction products of 10- (bottom), 35- (middle), and 120-min (top) reactions in THF-df ...

NMR and GPC Characterization of the Pentane-Soluble Products. Figure 8 shows the proton-decoupled NMR spectrum of the pentane-soluble products of a 35-min reaction after removal of tetralin... 

Figure 8. Proton-decoupled NMR spectrum of pentane-soluble products after removal of tetralin and...

Figure lA. Proton-decoupled NMR spectrum of i.-ascorbic acid in H2O, pH 2.0, 33°C. Short-range multiplicities arising from proton coupling are Cl (S), C2 (S), C3 (S), C4 (D), C5 (D), and C6 (T), where S, D, and T refer to singlet, doublet, and triplet, respectively. The direct and long-range... 

NMR Spectroscopy. All proton-decoupled NMR spectra were acquired on a Bruker AMX 400 NMR spectrometer operating at 100.62 MHZ. spectra were acquired using 32K data points, a spectral width of31250 Hz, a 90 pulse with a pulse... 

Fig. 7 Proton-decoupled NMR spectra (119 MHz) of apatite minerals acquired with MAS...

The carbon-13 proton decoupled NMR spectrum (Figure 4) of a 3 %w/v solution of econazole nitrate in deuterated dimethyl sulphoxide at ambient temperature (approximately 22°C), was obtained by using a Bruker AC300 spectrometer operating at a nominal frequency of 300 MHz. The chemical shifts are given in table 3 in p.p.m. 

Vittadini et al., (2001) investigated the media systems further with the proton decoupled NMR relaxation rate measurement using a 300 MHz NMR spectrometer (Bruker MSL 300) with a WALTZ pulse sequence. Acquisition parameters were 41 ms acquisition time, 9 /rs 90° pulse width, 100 ms recycle delay and 32°C sample temperature. Transverse relaxation rate Rz) was analyzed from line shape analysis after the system was... 

FIGURE 7.12. (a) H NMR spectrum, (b) nC and DEPT spectra, and (c) proton-decoupled NMR spectrum (121.4 MHz) of diethyl chlorophosphate in CDC13. The proton-coupled spectrum is shown as an inset. (Figure continues)... 

Figure 8. The effect of Mn2+ ions on the 13C proton-decoupled nmr spectra of 3-AMP in D20 (pD = 7-4) at 27°. Spectrum (a) is for the metal-free solution and the Mn2+ ion concentration is indicated in spectra (b) and (c). (Taken from Kotowycz and Hayamizu, 1973.)...

Spectra. The Fourier-transform, proton-decoupled NMR spectra of all the hydride and methyl complexes displayed a doublet of... 

Most other polysubstitution patterns on a benzene ring yield six different peaks in the proton-decoupled NMR spectrum, one for each carbon. However, when identical substituents are present, watch carefully for planes of symmetry that may reduce the number of peaks. 

FIGURE 4.15 The proton-decoupled NMR spectra of the three isomers of dichlorobenzene (25 MHz). 

The following alcohol undergoes ehmination in the presence of concentrated sulfuric acid, but the product shown is not its chief product. Instead, another isomeric six-carbon alkene forms. This product shows a large peak at 20.4 ppm and a smaller one at 123.4 ppm in its proton-decoupled NMR spectrum. Draw the stracture of the product, and interpret the spectrum. Outline a mechanism for the formation of the product that possesses this spectrum. 

Figure 10.10 is the proton-decoupled NMR spectrum of citronelloL We can easily assign certain features of the spectrum to particular carbon atoms of the molecule by examining the chemical shifts and intensities. For example, the peak at 131 ppm is assigned to carbon 7, while the taller peak at 125 ppm must arise from carbon 6, which has an attached hydrogen. The pattern appearing between 15 and 65 ppm, however, is much more complex and thus more difficult to interpret. 

Certain NMR instruments are also programmed to record the results of a DEPT experiment directly onto a proton-decoupled NMR spectrum. In this variation, called a NMR spectrum with multiplicity analysis, each of the singlet peaks of a proton-decoupled spectrum is labeled according to whether that peak would appear as a singlet, doublet, triplet, or quartet if proton coupling were considered. 

The stereochemistry at C4 is probably D although this has yet to be unequivocally established. The structure of (1) was further supported by a FAB mass spectrum which yielded a single intense peak with a m/e ratio of 133, corresponding to the expected molecular weight of the carboxylate anion. A final confirmation of the structure was obtained when the proton-decoupled NMR of (1) (Figure 6) was shown to be identical to authentic DL-4,5-dihydroxypentanoic acid ( ). 

Figure Five shows the proton decoupled nmr spectrum of thiopental sodium in DMSO-

Figure 8. Proton decoupled NMR spectra at 67.9 MHz of 145 bp hairpinned poly(dAdT) (12 mg in 1 mL) at 32°C. Peaks marked with a and b are from residual EDTA and ethanol. Total acquisition time, 62 h. Note the doubling of the C2 and C3 resonances (20).

Figure 8.1. Proton decoupled) nmr spectra of RuH(i7 -BH4)(ttp), 26, in i/g-toluene for the temperature range 230-378°K. Note that the resonance for begins to collapse in the temperature range 338-348°K, whereas the resonance of H/, remains. Both and H/> resonances collapse as the temperature is raised to 378 K. Reprinted with permission from J. Am. Chem. Soc. 104, 3898-3905 (1982). Copyright (1982) American Chemical Society.

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