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Long-range C-H couplings

The errors in the APT spectra may arise due to (a) variation in the relaxation times of different carbons, (b) wide variation in / h values, and (c) modulations caused by long range C- H couplings. A procedure known as ESCORT (Error Self Compensation Research by Tao Scrambling) has been developed to yield cleaner subspectra with reduced / cross-talk (Madsen et ai, 1986). This involves replacing the normal APT spectral... [Pg.101]

Fig. 5. Comparison of HMBC, D-HMBC and Field Gradient D-HMBC spectra of promoth-iocin B showing long range C- H couplings between methyl protons and relevant carbons of two oxazole units. Delay time was set to 500 ms. The sample (20 mg) was dissolved in... Fig. 5. Comparison of HMBC, D-HMBC and Field Gradient D-HMBC spectra of promoth-iocin B showing long range C- H couplings between methyl protons and relevant carbons of two oxazole units. Delay time was set to 500 ms. The sample (20 mg) was dissolved in...
Fig. 1.—Pulse sequence used to detect long-range C,H couplings. Reprinted with permission from Ref. 50. 1982 American Chemical Society. Fig. 1.—Pulse sequence used to detect long-range C,H couplings. Reprinted with permission from Ref. 50. 1982 American Chemical Society.
Fig. 2.—SELRESOLV sequence for inverse and selective detection of long-range C,H coupling constants. Reprinted from Ref. 58, 1990. Reprinted by permission of John Wiley Sons, Ltd. Fig. 2.—SELRESOLV sequence for inverse and selective detection of long-range C,H coupling constants. Reprinted from Ref. 58, 1990. Reprinted by permission of John Wiley Sons, Ltd.
The appearance of signals is described by the codes in the table below, b ric NMR spectra this means the appearance of the carbon signal - acquired without decoupling and under low resolution so that long-range C-H couplings can be ignored. [Pg.10]

TABLE 8. Long-range C-H coupling constants for cyclopropanes (1) (in Hz) ... [Pg.120]

Fine Splitting Pattern and Long-Range C- H Coupling Constants (HJ in Compounds 1, 11, 28, and 8... [Pg.158]

Further, because of the variation of long range C-H couplings and multiplicities, the extent of incorporation of satellite contributions within the line-width cutoff ranges will vary from group to group. Solvents often contain trace amounts of impurities, especially water, and can cause overlap problems, as can their isotopic satellites. [Pg.3266]


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See also in sourсe #XX -- [ Pg.2 ]




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