Spectroscopy Fourier transform NMR

Miller R J and Closs G L 1981 Application of Fourier transform-NMR spectroscopy to submicrosecond time-resolved detection in laser flash photolysis experiments Rev. Sc/. Instrum. 52 1876-85... 

Fourier transform spectroscopy in the radio frequency region has been applied most importantly in pulsed Fourier transform NMR spectroscopy, which is not a subject which... 

Fig. 2. Distribution of sdicon centers in soluble sdicate solutions from Si Fourier-transform nmr spectroscopy (7,37), where (—) represents (--------),...

Formate ion, bond lengths in, 757 electrostatic potential map of, 757 Formic acid, bond lengths in. 757 pKa of, 756 Formyl group, 697 p-Formyl benzoic acid, p/C, of, 760 Fourier-transform NMR spectroscopy (FT-NMR), 447-448 Fractional crystallization, resolution and, 307... 

The introduction of additional techniques such as Pulsed Fourier Transform NMR spectroscopy (PFT-NMR) has considerably increased the sensitivity of the method, allowing many magnetic nuclei which may be in low abundance, including 13C, to be studied. The additional data available from these methods allow information on polymer structure, conformation and relaxation behaviour to be obtained (1.18.20). 

D. Shaw, Fourier Transform NMR Spectroscopy, Studies in Physical and Theoretical Chemistry, Vol. 30, 2nd ed., Elsevier, Amsterdam, 1984. 

This approach has recently been extended to keto tautomers (Bassetti et al., 1988). Fourier-transform nmr spectroscopy is needed to record the signals of the small amounts of the keto isomers that are present. The carbonyl carbons of the keto form are to lower field of the corresponding atoms in the enol by ca. 10 ppm. The data were analysed into substituent factors relative to pentane-2,4-dione. Replacing the methyl groups of this compound with 2-thienyl, phenyl and t-butyl groups caused upfield shifts to the a-carbon of —3.14, —4.4 and —6.5 ppm, respectively, when the substituents were introduced at this site. 

Fourier transform NMR spectroscopy, polyethylene thermal oxidation, 695 Fourier transform-Raman spectroscopy hydroperoxides, 692 nitrile hydrolysis, 702 see also Raman spectroscopy Four-memhered peroxides, 164, 1212-13 FOX (Xylenol Orange-ferric complex) assay hydrogen peroxide determination, 628, 632, 657, 658... 

It can be shown by 13C Fourier transform NMR spectroscopy at — 78 °C that a six-membered peroxide is an intermediate which disappears completely on warming, with formation of the observed reaction products. The extrusion of nitrogen from the six-membered peroxide yielded the four-membered peroxide (equation 25) accompanied by light emission103. 

Fourier transform NMR spectroscopy, on the other hand, permits rapid scanning of the sample so that the NMR spectrum can be obtained within a few seconds. FT-NMR experiments are performed by subjecting the sample to a very intense, broad-band, Hl pulse that causes all of the examined nuclei to undergo transitions. As the excited nuclei relax to their equilibrium state, their relaxation-decay pattern is recorded. A Fourier transform is performed upon this relaxation-decay pattern to provide the NMR spectra. The relaxation-decay pattern, which is in the time domain, is transformed into the typical NMR spectrum, the frequency domain. The time required to apply the Hl pulse, allow the nuclei to return to equilibrium, and have the computer perform the Fourier transforms on the relaxation-decay pattern often is only a few seconds. Thus, compared to a CW NMR experiment, the time can be reduced by a factor of 1000-fold or more by using the FT-NMR technique. 

Uetake, N. 1987. Determination of degradation products in tributyl phosphate using 31P Fourier transform NMR spectroscopy. Analyst 112 445-448. 

D. Shaw, Fourier Transform NMR Spectroscopy , Elsevier, Amsterdam, 1976. 

Fourier transform NMR spectroscopy, although used extensively to study 13C and 15N nuclei, has only very recently been applied to ll9Sn. (27, 35-40,42—44)... 

The development of Fourier transform NMR spectroscopy made carbon NMR (13C NMR or CMR) possible, and high-field superconducting spectrometers allowed it to become nearly as convenient as proton NMR ( H NMR). Carbon NMR determines the magnetic environments of the carbon atoms themselves. Carbonyl carbon atoms, alkyne carbon atoms, and aromatic carbon atoms all have characteristic chemical shifts in the 13C NMR spectrum. 

Fourier transform NMR spectroscopy. The FT NMR spectrometer delivers a radio-frequency pulse close to the resonance frequency of the nuclei. Each nucleus precesses at its own resonance frequency, generating a free induction decay (FID). Many of these transient FIDs are accumulated and averaged in a short period of time. A computer does a Fourier transform (FT) on the averaged FID, producing the spectrum recorded on the printer. 

Related reviews have been published on the use of NMR in pesticide analysis ( 1), metabolic studies (2,2) drug metabolism (4,2), and medicinal cKemistry (6,7). Since nfost of these reviews as Well as many texts contain introductions to NMR, none will be presented here. Furthermore, an audio course on Fourier Transform NMR Spectroscopy is also available (8). Since structural characterization is often based on empirical correlations, we have found compilations of proton spectra by Aldrich, Sadtler, and Varian (9-11) and carbon spectra by Breitmaier et al. and Bruker (12,13) to be useful. Becker (14) has presented extensive lists oT references that contain useful compilations of NMR data (pp 77 and 106). Techniques... 

In the last years the technique of Fourier transform NMR spectroscopy has become widely appreciated for its speed and increased sensitivity it has especially become the method of choice for studies of the less sensitive nuclei, such as 13C or 15 N. In principle, the same information is contained in the slow passage and Fourier-transformed, pulse-excited spectra, and each may be optimized for resolution or for studies of particular features of the spectrum. Fourier transformation is nor-... 

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