The-modulated spin-echo

APT Attached proton test, a modification of the. /-modulated spin-echo experiment to determine CH multiplicities, a less sensitive alternative to DEPT... 

While setting up for the previous spectra, we obtained the spectrum opposite. The spectrum has been phased to correct the phase of the highest field methyl signal. Individual signals are expanded across the spectrum so that their phases can be seen more clearly the phase errors cannot be removed. Such phase problems may be generated in several ways, but in this case one parameter was misset in the /-modulated spin-echo sequence. What is the most likely source of this problem ... 

Let us investigate what happens when we alter the normal, 3C ( H experiment in Figure 12.2 by using the /-modulated spin echo pulse sequence shown in Figure 12.8a. This pulse sequence is closely related to the spin echo technique described in Section 3.6.3. 

EXAMPLE 12.11 How will the appearance of a quaternary carbon signal obtained using the /-modulated spin echo technique vary with x ... 

EXAMPLE 12.12 Draw the. /-modulated spin echo 13C spectrum of 2-chlorobutane (Example 12.6) that results from using x = 8 ms. 

D J-resolved NMR experiments are a conceptual amalgamation of two topics discussed above, the /-modulated spin echo and the two-dimensional characteristic of the spin—lattice relaxation experiments. As the name of these experiments implies, scalar coupling information, /, will be displayed in the one frequency domain chemical shift information will be presented in the second frequency domain. The simplest 2D/ experiments sort chemical shift information in the detected time domain, labeled by convention, while the heteronuclear scalar couplings of each carbon are sorted into the indirectly determined time domain, tj (do not be confuse lower case h with the spin—lattice relaxation time, Tj). 

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