Chemical shift parameters for

Summary of Chemical Shift Parameters for the Trityl Cation 16, Phenylindanyl Cation 13, Cyclopentenyl Cation 8, Methylindanyl Cation 12, tert-butyl Cation 2, and Methylcyclopentyl Cation 17... 

Summary of Chemical Shift Parameters for the Donor-Acceptor Complex between Acetone and a Variety of Lewis and Br0nsted Acids... 

Table 14 13C Substituent Chemical Shift Parameters for Pyrrole Derivatives 1...

Bell, H.M., Bowles, D.B., and Senese, F., Additive NMR chemical shift parameters for deshielded methine protons, Org. Magn. Reson., 16, 285, 1981. 

A correlation between the proton chemical shift parameter for the 3-proton of the diazepine ring and the charge density at the 3-carbon atom was also demonstrated.42 The results were quite distinct and separate from those obtained for dihydrodiazepines. 

Relationships of Chemical Shift Parameters " for Allenes, Ketene Imines, and Ketenes with Nuclear Charges of the Heavy Atoms in the Cumulenic Functionality (89<7)... 

Table II. Chemical Shift Parameters for Substitutions at the Sites of Glycerol, of Erythritol and of Adonitor...

Chemical shift parameters for rigid and flexible Tyr-o-Ala-Phe and Tyr-L-Ala-Phe tripeptides in the soHd state were established on the basis of 2D PASS experiments [94]. The same approach was employed to investigate the influence of the stereochemistry of alanine residue on molecular properties in Tyr-Ala-Phe-Gly tetrapeptide [95]. Very recently, this experiment was performed on Leu- and Met-enkephalins (Tyr-Gly-Gly-Phe-Leu and Tyr-Gly-Gly-Phe-Met, respectively) [96]. 

T. Pawlak, K. Trzeciak-Karlikowska, J. Czemek, W. Ciesielski, M.J. Potrzebowski, Computed and experimental chemical shift parameters for rigid and flexible YAF peptides in the solid state, J. Phys. Chem. B 116 (2012) 1974—1983. 

The rehability of these analytical methods may be questionable when chemical shift differences of derivatives are of the same magnitude as variations encountered from solvent, concentration, and temperature influences. Reported fluorine chemical shift ranges for tnfluoroacetylated alcohols (1 ppm), p-fluorobenzoylated sterols (1 ppm), and p-fluorobenzoylated ammo acids (0.5 ppm) are quite narrow, and correct interpretation of the fluonne NMR spectra of these denvatized mixmres requires strict adherence to standardized sampling procedure and NMR parameters. 

The sensitivity of 13C solid-state chemical shifts to small conformational changes is well illustrated by the case of i-PB. Table 1 summarizes some chemical shifts differences for the forms, which have been interpreted in terms of variations of the y-shielding parameter corrected for the deviations, with respect to the exactly G conformations, in the slightly different nearly gauche — nearly trans sequences, characterizing the three crystalline forms of i-PB [116]. 

Several methods have been developed to determine the chemical shift anisotropies in the presence of small and large quadrupolar broadenings, including lineshape analysis of CT or CT plus ST spectra measured under static, MAS, or high-resolution conditions [206-210]. These methods allow for determination of the quadrupolar parameters (Cq, i)q) and chemical shift parameters (dcs, //cs> <5CT), as well as the relative orientation of the quadrupolar and chemical shift tensors. In this context, the MQMAS experiment can be useful, as it scales the CSA by a factor of p in the isotropic dimension, allowing for determination of chemical shift parameters from the spinning sideband manifold [211],... 

C NMR spectroscopy of 1,7-dioxa- (314), l-oxa-7-thia- (315), and 1,7-dithiaspiro[5.5]undecane (316) and many of their derivatives, with special emphasis on stereoelectronic and steric effects governing the configurational and conformational properties of these compounds (484-486). This work showed that chemical-shift parameters developed for six-membered carbocyclic compounds in chair conformations (149) could be applied successfully only to sulfur and not to oxygen heterocycles (486). 

Accumulated NMR data support the proposal that the chemical shift for an olefinic carbon of monoenyl compounds can be calculated with ethylene as a reference [ 184]. A similar method was applied to the polyenyl Type I components with a conjugated system to estimate chemical shift parameters. Using 1,3-butadien for the base values (C 117.6 and 137.8 ppm), the chemical shift... 

We demonstrate that the physical properties of Xe adsorbed in mesoporous MCM-41 molecular sieves can be deduced from the analysis of the variable temperature l2,Xe NMR chemical shift data. For example, the interactions between the adsorbed Xe and the wall of the adsorbent, 8S. Our results indicate that the interactions arise from Xe adsorbed in mesoporous MCM-41 deviates significantly from not only the bulk Xe, but also from Xe adsorbed on microporous adsorbents or polymer surfaces. At a given temperature T, the pore size dependence of 8S can be described by the empirical relation 8,(T, d) = A(T)/(d + B(T)). The two temperature-dependence parameters were expressed by polynomial functions whose temperature coefficients were also revealed explicitly to the second order. 

A semi-empirical molecular orbital method for the correlation of charge distributions with 13C shifts in amino acids was described [95]. Plotting of chemical shift parameters versus charge density changes of a-carbon atoms relative to the corresponding atoms in the parent hydrocarbons permits prediction of the chemical shifts of the a-carbons with an accuracy of about 10%. However, the slope (280 ppm per electron) in Fig. 5.12 is... 

---