19F NMR

Mooney, E F An Introduction to 19F NMR Spectroscopy, Heyden Sons, London, 1970... 

Howell and Moss [289] confirmed, by 19F NMR spectroscopy, that NbOF52 complex is present in hydrofluoric acid solutions of up to 30%. Increase in HF concentration leads to the formation of NbF6 complex ions. 

The product 6 is a stable high melting solid which has 19F NMR chemical shifts that very closely resemble those of dodecafluorotricyclobutabenzene which therefore suggests a ring current. 

The anionic pentafluorophenyls have square pyramidal structures but are evidently non-rigid in solution (19F NMR shows all ligands equivalent). The neutral adducts are also square pyramidal (apical C6F5, trans-L) [192],... 

F-NMR measurement after acetylation of the hydroxy groups with triflnoroacetic anhydride277 or after formation of hexafluoroacetone adducts278. ... 

F-NMR analysis not only permits an accurate quantitative determination erf hydroxy groups but also provides valuable information on their nature and their location. This not the case with lH-NMR measurements which have been carried out on samples modified by reaction with (CH3)3SiCl329 or with naphthalene isocyanate. 

The correlation analysis of spectroscopic properties in terms of a,- and crR-type parameters has been very important. Substituent effects on 19F NMR shielding in... 

This subject has been associated with the development of the or and type scales almost from the start74 (see Section II.B), but the first paper in which sulfinyl and sulfonyl groups played a part appears to have been one by Taft and coworkers in 196367. The main object of this paper was to study the effect of solvent on the inductive order by 19F NMR measurements on a large number of mcta-substituted fluorobenzenes in a great variety of solvents. The relationship between the NMR shielding parameter and selected systems as equation 10 ... 

For SOMe and S02Me the values of as determined through chemical reactivities in weakly protonic solvents are quoted as 0.52 and 0.60 respectively. These provide a point of reference for consideration of the values determined through 19F NMR studies. The values for these substituents as determined in normal solvents are given as +0.49 and... 

TABLE 10. a, and aR constants for SOzMe based on 19F NMR in fluorobenzene and fluoronaphthalene systems117... 

Similarly, the Kass determined by the H NMR chemical shift of CHC13 in the presence of sulphoxides can be correlated well with the association constants obtained both on the basis of the IR stretching shift (AvOH) of phenol in the presence of sulphoxide and also with the 19F NMR chemical shifts of p-fluorophenol (<5,F). 

The results are in accordance with those obtained by Taft and colleagues80,81. These authors have measured the 19F NMR chemical shifts of p-FC6H4OH in the presenceof 60 bases including sulphoxides (DMSO, methyl phenyl, methyl p-nitrophenyl, diphenyl, tetramethylene sulphoxide) and determined the association constants K for the hydrogen bond shown in equation 15. 

NMR chemical shift data from die protons ortho or para to the electron-withdrawing group can be used to determine the reactivity of the monomer indirecdy.58 Carbon-13 and 19F NMR can be used to probe the chemical shift at the actual site of nucleophilic reaction. In general, lower chemical shifts correlate widi lower monomer reactivity. Carter reported that a compound might be appropriate for nucleophilic displacement if the 13 C chemical shift of an activated Buoride ranges from 164.5 to 166.2 ppm in CDC1359. 

Maryott A. A., Farrar T. C., Malmberg M. S. 35C1 and 19F NMR spin-lattice relaxation time measurements and rotational diffusion in liquid CIO3F. J. Chem. Phys. 54, 64-71 (1971). 

A PET oligomer isolation method has utilised chloroform extraction in a Parr bomb lined with a Teflon-TFE fluoro-carbon resin [40]. The analytics of fluoropolymer processing aids (combustion analysis, XRF, EUR, 19F NMR, OM) have recently been described [29]. Combustion analysis (Parr Oxygen Bomb Calorimeter) can be used for quantitative analysis... 

The assumption is made at present that elemental combustion analysis for carbon, hydrogen, and fluorine provides a good approximation to the extent of incorporation of fluoroalkyl residues, i.e. alcohols and ethers. We have ruled out trifluoromethylcarbonyl groups since no evidence is seen for their presence in either the infrared spectra or the 19F-NMR spectra. Thus, our values for percent modification reflect the best fit of the combustion data to an idealized stoichiometry for the product in Equation 1, where (m+n+o) = 100, and the percent modification (% mod.) is given by the expression [100 x (m+o)/(m+n+o)], equivalent to the number of fluoroalkyl residues per one hundred methylenes. An appropriately normalized formula was used to fit the data for polypropylene (sample 10). 

To aid in the characterization of the modified polymer samp os 1-10, and of the mixtures 11 and 12 obtained from functionalizing the two cycloalkanes, we prepared the model fluoroalkanols 13 and 14 as shown in Equation 2 (11-12), and the model fluoroalkyl ethers 15 and 16 as shown in Equation 3 1 3). Compounds 13 and 15 were previously isolated by- the Dupont group (8) from their mixture 11. Products 13-16 proved to be good comparison compounds for the infrared spectra, and particularly- for the 19F-NMR spectra. The I9F-NMR signal for the fluoroalkanol is approximately 1 ppm downfield from that of the fluo-roalky.l ether, which is enough to get semiquantitative ratios of... 

The cyclometalated dichlorocarbonyliridium(III) complex [IrCl2(CO) PPh2CH2C(tBu)=N-N=CH-(C6F4) ], (231), has been characterized by 31P, 13C, 19F NMR spectroscopy, and a singlecrystal diffraction study.403... 

The zinc teflate Zn(OTeF5)2 has been synthesized and characterized by IR and 19F NMR spectroscopy. The interaction with a number of weakly coordinating solvents was studied and the single-crystal X-ray structures determined for nitrobenzene derivatives [Zn(OTeF5)2 (PhN02)2]2 and Zn(0TeF5)2(PhN02)3.428... 

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