INADEQUATE Incredible Natural

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 NMR techniques discussed so far provide information about proton-proton interactions (e.g., COSY, NOESY, SECSY, 2D y-resolved), or they allow the correlation of protons with carbons or other hetero atoms (e.g., hetero COSY, COLOC, hetero /resolved). The resulting information is very useful for structure elucidation, but it does not reveal the carbon framework of the organic molecule directly. One interesting 2D NMR experiment, INADEQUATE (Incredible Natural Abundance Double Quantum Transfer Experiment), allows the entire carbon skeleton to be deduced directly via the measurement of C- C couplings. 

There is also the rather famous experiment known as 2D INADEQUATE (Incredible Natural Abundance DoublE QUAntum Transfer Experiment) which allows us to correlate carbon-13 with carbon-13. Potentially this experiment is very useful, since it allows us to see directly which carbon atoms are directly bonded. However, you will remember that the natural abundance of carbon-13 is only 1.1%, so a carbon-13/carbon-13 correlation requires us to detect only about 0.01% of the carbon nuclei present. Thus the experiment is very insensitive and requires large amounts of both sample and measuring... 

High on any NMR spectrocopist s wish list would be a technique that could be used to establish connectivities directly between carbon atoms. Such a technique does exist and it goes by the name of INADEQUATE (incredible natural abundance double quantum transfer experiment). Whilst this might sound fantastic in theory, everything in the garden is far from rosy. 

INADEQUATE incredible natural abundance double quantum transition experiment... 

On the other hand, the digermirane (18) reacts with Cgo to afford the 1,4-adduct (19, twist form) selectively15. The structure of the 1,4-adduct was confirmed by 13C-13C INADEQUATE (Incredible Natural Abundance Double Quantum Experiment) spectroscopy (equation 5). The rate of disappearance of Cgo was suppressed by addition of diazabicyclo[2.2.2]octane and 1,2,4,5-tetramethoxybenzene. Furthermore, the reaction was completely inhibited by addition of rubrene as triplet quencher. One plausible rationale for these observations is that an exciplex intermediate may be responsible for formation of the products (Scheme 6). 

Combination of HETCOR with COSY and TOCSY provides very useful but indirect information on the proximity of particular carbon atoms. For structure elucidation, a direct method based on Jcc is desirable, but with a natural abundance of only 1.1%, the probability of having two 13C nuclei directly bonded to each other is only about 1 in 10,000. Nevertheless, with sufficient sample, it is possible to obtain the information via INADEQUATE (incredible natural... 

Whereas the structural assignment by one-dimensional 13C NMR spectroscopy is unambiguous in the case of D2-Cj(,2,51 Achiba and co-workers were able to determine the carbon atom connectivity by 2D 13C NMR INADEQUATE (incredible natural abundance double-quantum transfer experiment) analysis performed on an isotopically enriched sample (20% 13C).58 In particular, they found that the observed chemical shifts correlate well with the curvature of the spheroid, the more strongly pyramidalized carbon atoms being shifted toward lower magnetic field. 

ID INADEQUATE (Incredible Natural Abundance Double Quantum Transfer Experiment)... 

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-... 

INADEQUATE Incredible Natural Abundance DoublE QUAntum Transfer Experiment (for determining what CC bonds are present)... 

D INADEQUATE (incredible natural abundance double-quantum transfer experiment) enables direct observation of neighbouring l3C-l3C correlation and has been applied to poly(vinyl alcohol)199 and polypropylene.206 For example, the CH carbon in the rrrr pentad has two cross-peaks with hexad methylenes of rrrrr and rrrrm. 

INADEQUATE Incredible natural-abundance double-quantum transfer experiment 5.8... 

HMBC. Heteronuclear multiple bond correlation. HMQC. Heteronuclear multiple quantum correlation. HSQC. Heteronuclear single quantum correlation. INADEQUATE. Incredible natural abundance double quantum transfer. 

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