Signals correlation with proton spectra

The proton-carbon correlation spectrum, which tells you directly which signals in the proton spectrum correspond with which signals in the broad-band decoupled carbon spectrum. This information, together with the integration values and the multiplicities obtained from APT (or DEPT), is invaluable in putting together the molecular fragments. 

A second 2D NMR method called HETCOR (heteronuclear chemical shift correlation) is a type of COSY in which the two frequency axes are the chemical shifts for different nuclei usually H and With HETCOR it is possible to relate a peak m a C spectrum to the H signal of the protons attached to that carbon As we did with COSY we 11 use 2 hexanone to illustrate the technique... 

One-dimensional spectra obtained by projecting 2D spectra along a suitable direction often contain information that cannot be obtained directly from a conventional ID spectrum. They therefore provide chemical shift information of individual multiplets that may overlap with other multiplets in the corresponding ID spectra. The main difference between the projection spectrum and the ID spectrum in shift-correlated spectra is that the projection spectrum contains only the signals that are coupled with each other, whereas the ID H-NMR spectrum will display signals for all protons present in the molecule. 

The assignments of the purine resonances [460, 749, 751, 758, 759, 761] of proton broadband-decoupled 13C NMR spectra of nucleosides and nucleotides are made using the following aids [749, 761] Correlation with the signals of the parent bases and analogous nucleosides or nucleotides comparison of the 13C NMR spectrum with that of a specifically analogue correlations of the chemical shift values with the 7r-electron densities [749, 761] and, in addition, proton off-resonance decoupling, which affords the identification of quaternary carbon atoms. 

Buzas et al. (70) recorded the spectrum of emetine dihydrochloride as well as several emetine analogs and synthetic intermediates. Most of the assignments correlated with Wenkert s data however, C-l to C-7 and C-3 and C-4 were shielded upon nitrogen protonation (8, 12). It was observed that protonation of the nitrogen had an additional effect on the quinolizidine portion of emetine since C-l lb, C-3, and C-6 were not observed at ambient temperatures C-4 was also quite broad. These signals became visible and sharpened at higher temperatures. 

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