N.M.R. chemical shift—charge density correlations

Charge density-N.M.R. chemical shift correlations in organic ions, 11, 125 Chemically induced dynamic nuclear spin polarization and its applications, 10, 53 Chemiluminescence of organic compounds, 18, 187 CIDNP and its applications, 10, 53 Conduction, electrical, in organic solids, 16, 159... 

Wagner claims that this structure con-esponds to HNg, but no consideration was given to the effect of the H atom. He carried out similar calculations on various pseudohalide anions and was able to show that the pA of the corresponding acids varies linearly with the difference in the 7r-energy between the ions and their acids. Linear correlations were also found betw een (a) calculated bond orders and stretching force constants, (b) calculated charge densities and n.m.r. chemical shifts. 

Details of studies on the n.m.r. spectra of substituted pyridazines, pyrimidines, and pyrazines have appeared. Calculated (MINDO/2) charge densities have been correlated with substituent-induced chemical shifts of these diazines. ... 

The chemical shifts of ring protons and attached methyl groups have been correlated with calculated charge densities. The n.m.r. data confirm the non-uniform distribution of charges suggested by the simple resonance picture. Thus in 1,2-dithiolium cations, protons attached to the 3- and 5-positions have signals at lower field (between t = — 0.6 and t = 0.1) than those attached to the 4-position (ca. t = 1.5) and methyl groups are similarly affected. 

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. 

A rough correlation of 8 carbene carbon with the frequency of the metal to ligand charge transfer band was found. The energy of the band increased as the electron donating properties of R decreased, due to the increased stabilization of the carbene pz orbital with increasing electron delocalization (chemical shift of the carbene carbon will be electron density differences. 

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