F-NMR

Two methods have been described for determining the compositional analysis of these copolymers one based on high-resolution continuous and Fourier transform F-NMR, and the other on Py-GC [32, 33]. 

When the composition of a single component in a mixture is required, it is necessary to relate the component resonance to that of another compound, an internal standard. 

The value obtained is in excellent agreement with those obtained by mass balance. 

To measure the composition of a single component in a mixture, it is necessary to relate the component resonance to that of another compound (an internal standard) which is of known chemical composition and has been added in known weight to a known weight of unknown. Brame and Yeager [132] used dichlorobenzotrifluoride as an internal standard in the continuous wave method for determining the compositional analysis of both repeat units in hexafluoropropylene - vinylidene fluoride copolymers. This work demonstrated the utility of the Fourier transform NMR method in quantitative analysis of the copolymer, in relation to results obtained by continuous wave F-NMR and proton NMR. 

The monomer composition of the series of copolymers was calculated from the pyrolysis data and compared to that calculated from the NMR data. These data are summarised in Table 4.11. The difference in weight% calculated for the two techniques, averaged for hexafluoropropylene 6.0% and for vinylidene fluoride 0.85%. 

SD standard deviation HPF hexafluoropropylene VF2 vinylidene fluoride Reprinted with permission from J.T. Blackwell, Analytical Chemistry, 1976, 48, 13, 1883 [133]. 1976, American Chemical Society [133]  

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Despite these simplifications, a typical or F NMR spectrum will nomially show many couplings. Figure BTl 1.9 is the NMR spectrum of propan-1-ol in a dilute solution where the exchange of OH hydrogens between molecules is slow. The underlymg frequency scale is included with the spectrum, in order to emphasize how the couplings are quantified. Conveniently, the shift order matches the chemical order of die atoms. The resonance frequencies of each of the 18 resolved peaks can be quantitatively explained by the four... 

Speclnfo Chemical Concepts GmbH, Germany spectral data nu- meric, struc- ture 150000 subst., 80000 C-NMR, 850 N-NMR, 670 O-NMR, 1750 F-NMR, 2000 P-NMR, 17000IR, 65 000 MS Chemical Concepts GmbH online periodi- cally www.chemicaJ- conctpts.com/ products.htm... 

Kinetic results (5) and F nmr experiments (6) illustrate cleady that the hydroxyduoroborates are in rapid equiUbrium and easily exchange duoride. 

Simple and Complex Organic Molecules. Using modem direct fluorination technology, the synthesis of even the most complex perfluorocarbon stmctures from hydrocarbon precursors is now possible. For example, syntheses of the first perfluoro crown ethers, perfluoro 18-crown-6, perfluoro 15-crown-5, and perfluoro 12-crown-4 (54) have been reported. Perfluoro crown ethers (54,55) are becoming important as the molecules of choice for many F-nmr imaging appHcations (56) in humans and are particularly effective in brain and spinal diagnostics when... 

The incidence of these defects is best determined by high resolution F nmr (111,112) infrared (113) and laser mass spectrometry (114) are alternative methods. Typical commercial polymers show 3—6 mol % defect content. Polymerization methods have a particularly strong effect on the sequence of these defects. In contrast to suspension polymerized PVDF, emulsion polymerized PVDF forms a higher fraction of head-to-head defects that are not followed by tail-to-tail addition (115,116). Crystallinity and other properties of PVDF or copolymers of VDF are influenced by these defect stmctures (117). 

The F nmr spectrum of this compound gives only one signal over a wide range of temperatures, a result attributed to Berry pseudorotation (144). No alkyl- or aryltetrabromoarsorane has been reported. There is, however, an early report on the preparation of tetraiodomethylarsorane from methylarsonic acid and hydriodic acid (145). 

Peroxy acid oxidation of (17) gave sulfoxide (18) whose F NMR spectrum showed equivalent CF3 groups even at —95 °C (76JA4325). Tlie rate ratio for the sulfur walk in (18/17) is an astounding 10 ° at 25 "C theoretical reasons for the difference have been discussed (80JA286i). 

F NMR, 4, 569 <72JCS(P2)1733> Benzo[b]furan-3-carboxylic acid, 2-methyl-, methyl ester... 

Furan, 3-(4,8-dimethyl-3,7-nonadienyl) — see Dendrolasin Furan, 2,5-dinitro-synthesis, 4, 711 Furan, 2,5-diphenyl-bischloromethylation, 4, 607 Furan, 3-ethoxycarbonyl-2,5-dimethyl-synthesis, 4, 659 Furan, 2-ethyltetrahydro-synthesis, 3, 776, 4, 711 Furan, fluoro- F NMR, 4, 564 H NMR, 4, 564 Furan, halo-... 

Pyrimidine, 2,4,5,6-tetrachIoro-dyes from, 1, 321 Pyrimidine, tetraSuoro- F NMR, 3, 63 Pyrimidine, 2,4,5,6-tetrafluoro- F NMR, 3, 63 Pyrimidine, tetrahydro-acetonin synthesis, 3, 118 polymers, 1, 314 Principal Synthesis, 3, 115 Pyrimidine, 1,4,5,6-tetrafaydro-... 

MEASURING SURFACE PARAMETERS VIA I F NMR OF ADSORBED ORGANOFLUORINE PROBE MOLECULES... 

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