Resonance signals

Morris G A and Freeman R 1979 Enhancement of nuclear magnetic resonance signals by polarization transfer J. Am. Chem. See. 101 760-2... 

The chemical shifts of in natural abundance have been measured for thiazole and many derivatives (257,258). They are given in Tables 1-37 and T38. These chemical shifts are strongly dependent on the nature of the substituent CNDO/2 calculations have shown (184) that they correlate well with the ((t+tt) net charge of the atom considered. As a consequence, the order of the resonance signals is the same for protons and for carbon atoms. 

An n.m.r. spectrum of cyclobutylamine in carbon tetrachloride showed no resonance signals at less than 1 p.p.m. from tetramethylsilane. This suggests that no cyclopropylcarbinyl-amine was formed by rearrangement during the reaction. 

Isomer ratios of mixtures of 5//-dibenz[c,e]azepines have been determined by integration of the C7 methylene resonance signal in their HNMR spectra.48... 

Unfortunately, many other nuclei of importance in chemistry, such as and 0, have nuclear spin values of 0 and hence do not give nuclear resonance signals in a magnetic field. 

Johnson, K., Sutcliffe, L., Edwards, RH.T. and Jackson, M.J. (1988). Calcium ionophore enhances the electron spin resonance signal from isolated skeletal muscle. Bitxhim. Biophys. Acta 964, 285-288. 

Fig. 8.16 Fe Mossbauer spectra of [Fe2 (PMAT)2](BF4)4-DMF at selected temperatures. At 298 K, the only quadrupole doublet is characteristic of iron(II) in the HS state. SCO from HS to LS occurs at one Fe(II) site of the dinuclear complex at ca. 225 K. The second Fe(II) site remains in the HS state, but feels the spin state conversion of the neighboring atom by local distortions communicated through the rigid bridging ligand, giving rise to a new quadrupole doublet (dark gray), i.e., HS in [HS-LS], in the Mossbauer spectrum. The intensity ratio of the resonance signals of HS in [HS-LS] to that of LS (black) in [HS-LS] is close to 1 1 at all temperatures (from [32])...

In view of the highly strained o- B—C bonds of 74-75, there is experimental evidence that such ir-bonding is actually responsible for the stability of the ring to cleavage. For example, addition of pyridine to colorless 74d generates an intense yellow color and many new resonance signals in the l3C-NMR spectrum consistent with isomeric zwitterions 76a,b. Addition of r-BuOH (which does not itself react with 74d) yields borinate ester 77 (Scheme 3). These results are consistent with the interpretation... 

If a molecule contains one or more unpaired electrons it is usually possible to detect an electron spin resonance signal and at a very low concentration of unpaired electrons, commonly 1018 spins with modem instruments. Several pieces of information can be obtained in this way. The number of unpaired spins can be found, the symmetry of the molecule in the region of the unpaired electron can be determined, and, if the unpaired electron is delocalized over nuclei with nuclear spins, then the extent of delocalization can be determined. Perhaps more importantly for our purpose, the rotational time of molecules can be determined from line shape studies. 

Table 10. Electron spin resonance signals of metalloproteins...

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