NUCLEAR MAGNETIC RESONANCE CORRELATION TABLES

CHAPTER 13 Structure Determination Nuclear Magnetic Resonance Spectroscopy Table 13.3 Correlation of Chemical Shift with Environment... 

Correlation tables for nuclear magnetic resonance spectroscopy 1423... 

In a comparison of chemical analytical methods to bioassays, results obtained using methods utilizing derivatives (DNP and 7 - hydroxyquinoline) combined with colorimetric or fluorimetric detection were not specific for acrolein and consistently did not correlate with those obtained from bioassays. Certain direct methods of detection (nuclear magnetic resonance (NMR), fluorescence, and differential pulse polarography) gave the best correlation to the bioassay results (see Table 6-1). 

Nuclear magnetic resonance spectra. As well as numerous routine reports of NMR spectra (see individual entries in the Appendix Table of Simple Pyrazines), a brief correlation of II NMR spectra for 2-alkyl-3,5,6-triph-enylpyrazines (243) and the corresponding 2,3-dihydro derivatives (244) has appeared 137 in addition, a comparative 13C NMR study of 2-styrylpyrazine (245) with other styryldiazines and some styrylazines has been reported.1428... 

The results of thermorheographic experiments presented in Table 7 show very high correlation with the pulsed NMR data in Table 2. Thus, Malaysian cocoa butter crystallizes quickly, and Brazilian is the slowest crystallizing, which correlates with the hardness of these cocoa butters as measured by pulsed nuclear magnetic resonance technology. 

The following correlation tables provide the regions of nuclear magnetic resonance absorptions of major chemical families. These absorptions are reported in the dimensionless units of parts per million (ppm) versus the standard compound tetramethylsilane (TMS, (CH3)4Si), which is recorded as 0.0 ppm. 

No attempt will be made here to review and correlate the large number of ultraviolet, infrared, nuclear magnetic resonance, and mass spectra that have been recorded, interpreted, and used in structure determination of pyridinols and pyridones. Articles that contain significant spectral data and/or discussions are noted in the Tables. The role of spectroscopic techniques, ionization constants, and dipole moments in the studies of structure and tautomerism of heterocyclic compounds has been reviewed recently by Albert. Although ionization constants have been used to estimate pyridinol-pyridpne equilibrium constants with some success, caution must be exercised about drawing conclusions from this type of data. ... 

A variety of approaches has been employed including chemical correlation with compounds of known absolute configuration, nuclear magnetic resonance spectroscopy for obtaining relative stereochemistry, X-ray diffraction, optical rotatory dispersion and circular dichroism. The attention of the reader is directed to the specific examples in the Tables where stereochemistry is defined and particularly to the review of Nielsen 419),... 

In addition, nuclear magnetic resonance (NMR) and infrared methods have been widely used. For example, the chemical shift of MA in benzene or acetone is concentration as well as temperature dependent, Silber et have thus determined equilibrium constants for the complexes. Also used successfully is analytical calorimetry. In Tables 6.10 and 6.11 are shown data for MA-benzene and MA-acetone complexes, respectively. Comparisons with those results from NMR studies are given. Obviously good correlations are obtained. Based on their data, 25% of MA (0.044 mole fraction) in benzene is present as complex whereas that number is 55% for MA (0.25 mole fraction) in ace tone. 

Over 100 SbCls affinity values are collected in Table 2.2. The sample of Lewis bases contains mainly oxygen bases and, among these, mainly carbonyl compounds. Only nine nitrogen bases (seven nitriles, one pyridine, one amine) have been studied. The scale lacks second-row bases, carbon bases and halogen bases. We have not reported the values estimated indirectly from correlations between DN and solvent basicity-dependent properties, such as nuclear magnetic resonance chemical shifts of the Na nucleus [27] or of the chloroform proton [28], These values would be valid only if there was no separation into families of bases in the correlation chart, which is rarely found. As shown in this book, family-dependent correlations between basicity-dependent properties are generally the norm. 

---