Homonuclear chemical shift correlation

Fig. 11.6 Pulse sequence for two-dimensional homonuclear chemical-shift correlation experiments. The gray box indicates the mixing sequence, with some examples shown in more detail a RFDR, b RIL, c C7, d DRAWS, e DREAM.

Concatenation of Polarization Transfer Steps into Homonuclear Chemical Shift Correlated Experiments. Application to Oligo- and Polysaccharides... 

In the case of an unknown chemical, or where resonance overlap occurs, it may be necessary to call upon the full arsenal of NMR methods. To confirm a heteronuclear coupling, the normal H NMR spectrum is compared with 1H 19F and/or XH 31 P NMR spectra. After this, and, in particular, where a strong background is present, the various 2-D NMR spectra are recorded. Homonuclear chemical shift correlation experiments such as COSY and TOCSY (or some of their variants) provide information on coupled protons, even networks of protons (1), while the inverse detected heteronuclear correlation experiments such as HMQC and HMQC/TOCSY provide similar information but only for protons coupling to heteronuclei, for example, the pairs 1H-31P and - C. Although interpretation of these data provides abundant information on the molecular structure, the results obtained with other analytical or spectrometric techniques must be taken into account as well. The various methods of MS and gas chromatography/Fourier transform infrared (GC/FTIR) spectroscopy supply complementary information to fully resolve or confirm the structure. Unambiguous identification of an unknown chemical requires consistent results from all spectrometric techniques employed. 

Section 7-7 Homonuclear Chemical-Shift Correlation Experiments Via Scalar Coupling 251... 

Section 7-10 Homonuclear Chemical-Shift Correlation Via Dipolar Coupling 267... 

Filiurr 5. Homonuclear Chemical Shift Correlated (Cosy <5i ZD-NMR Spectrum of Amodlaquine H>drochloride... 

Ulrich E L, Westler W M, Markley J L 1983 Reassignments in the H NMR spectrum of flavin adenine dinucleotide by two-dimensional homonuclear chemical shift correlation. Tetrahedron Lett 24 473-476... 

COSY = homonuclear chemical shift correlation spectroscopy NOESY = 2D nuclear Overhauser effect (NOE) spectroscopy HMQC = heteronuclear mulltiple-quantum coherence RELAY = relayed coherence transfer COLOC = correlation via long-range coupling HMBC = heteronuclear long-range coupling INADEQUATE = incredible natural abundance double quantum transfer experiment. 

Fig. 2. A 146-MHz, > P homonuclear chemical-shift correlated two-dimensional spectrum of an equimolar (50 mM) mixture of ADP and ATP. The data set (128 X 256) is disfjayed in the stacked-plot mode. Each trace corresponds to an increment in the evolution time. The data were acquired in 45 min. The stacked plot took 15 min to complete. The diagonal, which makes a 45 angle with the F, (ordinate) and Fj (abscissa) axes, reproduces the one-dimensional spectrum. The off-diagonal peaks correlate peaks on the diagonal that are spin-spin coupled to each other. Peak identifications can be found in Fig. 3.

As the data matrix for a homonuclear chemical-shift correlation experiment is symmetrical, the D F2 i) data set is identical to a Z)(F, data set. 

In Section II the methodology of the homonuclear chemical-shift correlated technique is discussed. Applications of the Jeener experiment are now described, showing how two-dimensional, chemical-shift correlated spectra provide insight into the assignment of complicated P spectra. 

Figure 8 contains the conventional and correlated 146-MHz P spectra for Ni (a-[18]ane P402) 2BF4 in acetonitrile. Inspection of the homonuclear chemical-shift correlation map unambiguously shows there are four... 

Section 11, A demonstrates how homonuclear chemical-shift correlated spectra provide additional information for NMR studies of phosphorus cell metabolites. Because the homonuclear method requires the presence of 3ip 3ip spin-spin coupling, no data are obtained for monophosphorylated... 

---