Coupling constants correlation diagram

The electronic spectra of several of the complexes have been studied and attempts have been made to correlate the absorption bands with the energy levels of proposed molecular orbital diagrams.254,255 An Rh-P coupling constant of 133 Hz has been observed in the 3IP NMR spectrum of [Rh(diphos)2]+.256... 

IPs) and coupling constants, and present the former in tabular form in Table 2 and as a correlation diagram in Fig. 1. The figure displays, in addition, schematic drawings of the molecular orbitals corresponding to the first two IPs to visualize their bonding properties and correlation in the series. 

There are two broad classes of 2D-NMR spectra. In the J-resolved spectra, the peaks in a spectrum are so spread that the chemical shifts are found in one dimension while the coupling constants occur in the second dimension. The second class covers correlated spectra which are basically correlation diagrams between two spectra. Thus the H-NMR spectrum may lie along one axis while the C-NMR spectrum lies on the other axis and the contours obtained at the cross-points allow one to correlate which protons in the H-NMR spectrum are attached to which carbon atoms in the C-NMR spectrum. 

Figure 4 Correlation diagram for the coupling constants Ja. The solid line represents the correlation for fixed Xi dihedral angles, and the dashed line shows the correlation with 30° uniform averaging. Values near the solid or dashed line may arise from a single con-former deviations from the line probably indicate significant side chain motion. Adapted from Ref. 21...

A detailed study of n.m.r. spectra has provided extensive data on chemical shifts and coupling constants in respect of a series of monophenyl-thiazoles, and their derivatives bearing alkyl and functional substituents in their hetero-rings. The chemical shifts were correlated with the net from electron density and energy diagrams, and the overall results were compared with those previously obtained in respect of thiazole and its methyl derivatives. 

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