Homonuclear INADEQUATE

INADEQUATE Incredible natural abundance double quantum transfer experiment, segregates AB or AX systems due to homonuclear one-bond couplings of less abundant nuclei, e.g. 

The INADEQUATE experiment is a homonuclear NMR technique in which coupling satellites are detected after suppressing the stronger... 

HSTLC microextraction High-speed TLC INADEQUATE analysis Homonuclear 7-correlated 13C... 

MO wave functions in the above form give equal importance to covalent and ionic structures, which is unrealistic in homonuclear diatomic molecules like H2. This should be contrasted with (/>Vb> which in its simple form neglects the ionic contributions. Both and i//MO are inadequate in their simplest forms while in the VB theory the electron correlation is overemphasized, simple MO theory totally neglects it giving equal importance to covalent and ionic structures. Therefore neither of them is able to predict binding energies closer to experiment. The MO theory could be... 

Today, a number of one- and two-dimensional NMR experiments are available for the detection of homonuclear Li, Li and Li, Li couplings. Aside from the COSY experiment, the double quantum filtered COSY (COSY-DQF), the TOCSY, and the ID and 2D INADEQUATE experiments [24] have been successfully employed. An attractive feature of all these experiments is their sensitivity for small scalar interactions which give rise to crosspeaks even if line splittings in the corresponding ID spectra are not resolved. This was first demonstrated with COSY experiments for a paramagnetic nickel complex [82] and for quadrupolar nuclei in the case of boron-11 [83]. 

In the case of Li, broad lines can lead to overlap for situations with small chemical shifts and this might give rise to artificial crosspeaks in Li, Li COSY experiments. If the chemical shift is sufficiently large, the larger Li, Li coupling (factor 2.64 compared with 7( Li, Li)) facilitates the experiment. Detection of homonuclear Li, Li coupling was also achieved by the Li, Li INADEQUATE experiment [93]. 

Two dimensional sequences are commonly used in solution state NMR spectroscopy to elucidate connectivity of atoms within molecular structures. Sequences are available for heteronuclear shift correlation, homonuclear correlation (COSY and INADEQUATE) and other sequences for longer-range connectivities. In general the basis of these... 

The pulse sequence INADEQUATE (Incredible Natural Abundance DoublE QVAntum Transfer Experiment) was developed by Freeman to suppress the usual (single-quantum) resonances and exhibit only the satellite (double-quantum) resonances. The pulse sequence is 90°-T-180y-T-90°-A-90. The homonuclear 180° pulse refocuses field inhomogeneities, but allows the vectors from different coupling arrangements to contin-... 

Homonuclear C- C INADEQUATE experiments are the most difficult and least frequently used. 

INADEQUATE Correlating coupled homonuclear spins of low natural abundance (<20%). Typically used for correlating adjacent carbon... 

Homonuclear correlation experiments are not just restricted to the standard COSY experiment, but also include the TOCSY and INADEQUATE experiments. The separation of TOCSY and INADEQUATE from the homonuclear COSY experiment is based on the different coherence evolution and transfer processes involved. Thus the TOCSY experiment is based on cross-polarization in contrast to the polarization transfer used in the homonuclear COSY experiments. INADEQUATE experiments are characterized by the double quantum state of two scalar-coupled nuclei during the tl period such that the second dimension (fl) is scaled into a double quantum frequency. Nevertheless these experiments can all be considered together because they are based on homonuclear scalar coupling and the fl and f2 dimension of the corresponding 2D spectra are related to the same nucleus. 

Starting with the basic INADEQUATE experiments the simulation focuses on the inherent disadvantage of homonuclear correlation experiments on nuclei with low natural abundance. 

D INADEQUATE experiments are also possible and these type of experiments are unique in that the fl dimension does not correspond to single quantum coherence frequency but to a double quantum coherence frequency. These double quantum coherences are observed because homonuclear coupling and chemical shift evolve simultaneously during the dO period and can not be suppressed. In Check its 5.4.3.3 and... 

NMR is the tool most widely used to identify the structure of triterpenes. Different one-dimension and two-dimension techniques are usually used to study the structures of new compounds. Correlation via H-H coupling with square symmetry ( H- H COSY), homonuclear Hartmann-Hahn spectroscopy (HOHAHA), heteronuclear multiple quantum coherence (HMQC), heteronuclear multiple bond correlation (HMBC), distortionless enhancement by polarisation transfer (DEPT), incredible natural abundance double quantum transfer experiment (INADEQUATE) and nuclear Overhauser effect spectroscopy (NOESY) allow us to examine the proton and carbon chemical shift, carbon types, coupling constants, carbon-carbon and proton-carbon connectivities, and establish the relative stereochemistry of the chiral centres. 

DQ spectroscopy is not only useful for homonuclear C— C correlation experiments which allow the identification of the backbone connectivity. In this section, the utility of other 2D DQ experiments which provide insight into, e. g., through-space proximities will be illustrated. As opposed to the solid-state INADEQUATE experiment introduced in the previous section, the experiments described in this section are based on the dipolar as opposed to the J coupling of spins. 

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