13C decoupling

Figure 24 H2BC pulse sequence. Thin and thick bars represent 90° and 180° pulses, respectively, while, and the dashed boxes represent 13C decoupling, t = i2 = l/[ /max + Vminl T, = 0.5/[Vmln + 0.07(Vmax - Vmin)]. T3 = 0.5/[Vmax - 0.07(Vmax - Vmln)] and S = S + t(90H), where S is the gradient delay. T denotes the constant-time delay.

Figure 26 Proposed HMBC pulse sequences68 for editing into two subspectra according to the number of directly attached protons being odd or even Filled and open bars refer to 90° and 180° pulses, respectively, while the dashed open boxes represent 13C decoupling. Recommended phase cycle 0 — x, —x, x, — x 02 = x, x, 4(—x), x, x ...

Fig. 8. Pulse schemes for 2H 2D NMR spectroscopy of weakly ordered, deuterated solutes (a) 2H Q-COSY, (b) 2H-13C HETCOR experiment with 13C decoupling, (c) 2H-2H COSY 2D experiment. (Reproduced by permission of American Chemical Society.)...

Figure 6.18 Stop-flow 2D WET-TOCSY spectrum of 3,5-dichloro-2-hydroxybiphenyl. Protons (H4.H6) of the chlorinated ring can be identified due to the magnetization transfer between the signals at 7.23 (H4) and 7.41 (H6) ppm. Conditions spectrometer, Bruker DRX 600 probe head, 4mm z-gradient LC probe. 13C decoupling was applied during the WET-pulse train and acquisition. The spectral size was 8k x 512 data points, with 16 scans per increment, and a 64 ms TOCSY mixing time...

Figure 7.3.1.7 A 13C-decoupled HMQC spectrum of 54 mM chloroquine diphosphate in D2O acquired with an inverse detection microcoil probe. The 740-nl F0bs contained 40 nmol (13 jig) of chloroquine. The data, 32 transients per slice, 1024 x 128 (x2, hypercomplex) points, were acquired in 3.6h. The data were zero-filled to 256 points in the 13C dimension. A 40° shifted sinebell function was applied, followed by Gaussian multiplication prior to Fourier transformation...

EXAMPLES OF ONE-BOND INVERSE CORRELATION (HMQC AND HSQC) WITHOUT 13C DECOUPLING... 

Figure 11.30 shows a portion of the HMBC spectrum of Product 2, including the alcohol region in both dimensions (3.2-4.4 in F2 = H and 67-85 ppm in F = 13C). The HSQC peaks are superimposed and shown in parentheses, and the resonances are shown above or below these peaks with an expansion of the ddd at 4.15 ppm. One-bond artifacts are clearly visible in the HMBC spectrum as wide doublets centered on the position of the 13C-decoupled HSQC crosspeaks (compare to the diagram in Fig. 11.11). In addition a fat HMBC crosspeak is observed between the new lH resonance at 4.15 ppm in F2 and the C-17 13C resonance at 82 ppm in F (Fig. 11.30, lower left side). This means that the CH-OH proton at the position of oxidation is two or three bonds away from C-17 Of the three possibilities (7, 11, and 15), it must be H-15. H-11 would be four bonds away and...

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