COSY NMR

Potassium silicate solutions are equally complex for example, an aqueous solution prepared from KOH and Si02 in which the ratio K Si is 1 1 contains 22 different discrete silicate anions as identified by Si COSY nmr studies. 

FIGURE 4.10 Stopped-flow H H-COSY NMR spectrum of (all- ) lycopene. (From Albert, K., On-Line LC-NMR and Related Techniques, John Wiley Sons Ltd., 131, 2002. With permission.)... 

FIGURE 4.18 Stopped-flow FFH-COSY NMR spectrum of (all-//) astaxanthin. 

In particular, DP9 presented ambiguities associated with the proton assignments from which the 13C assignments were derived. Thus, it was necessary to use the COSY method to assign the proton absorptions first. Homonuclear COSY NMR spectroscopy allowed unambiguous assignment of proton chemical shifts in all cases. 

The addition of an amino acid and subsequent conversion to the hydantoin were monitored on single beads using both one-dimensional H and COSY NMR.40 With beads of 400-750 pm holding 10-65 nmol of amino acid per bead, acquisition time of 3 min for ID and 40 min for COSY were sufficient when 1-4 beads were placed in the MAS rotor. 

Figure 4.26 500 MHz HH COSY NMR spectrum of ethyl benzoate in CDCI3...

The acquisition of a two-dimensional (2D) NMR spectrum gives the advantage of obtaining information about both the chemical shifts values 8 and the coupling system of each proton (the 2D plot allows us to establish the assignments of such coupling systems). Figure 5.2.5 depicts the stopped-flow 2D COSY NMR spectrum of all-E lycopene from a tomato extract. This was recorded within 24 h with a total of 280 increments and 256 transients. 

Figure 5.2.5 Stopped-flow COSY NMR spectrum of all-E lycopene from a tomato peel extract...

Fig. 17 1H, H-COSY NMR spectrum (in CDCl3) °f a dextran a tate propionate...

COSY NMR Two-dimensional correlated nulcear magnetic resonance... 

Bohlmann absorption band at 2784 cm indicated the cis relationship of protons H-5 and H-9 (5Z,92), trans antiparallel to the nitrogen lone pair, in accordance with the spectral features of 5,8-disubstituted indolizidines. The existence of three methyl triplets in the H NMR spectrum pointed to a trisubstituted indolizidine nucleus and the analysis of the H 2D COSY NMR spectrum, as well as the J coupling values observed and molecular modelling of the proposed structure, revealed that H-9, H-6 and H-5 occupied axial positions, according to the relative configuration depicted for indolizidine 223A.)... 

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