Methyl fluoride chemical shifts

The chemical shift differences observed for these 1-fluoro-l-methyl-f-butylcyclohexanes, the cis- and rrans-9-nuomdecalins, and for 1-fluoroadamantane provide insight regarding the significant influence of conformation upon fluorine chemical shifts in fluorocyclohexanes. The relative chemical shifts of these various cyclohexyl fluorides can be rationalized simply on the basis of what is commonly known as an anomeric effect. That is, a vicinal hydrogen that is rigidly anti to a fluorine substituent will exhibit an anomeric double-bond/no-bond... 

Both the chlorine and fluorine sulfonyl compounds strongly deshield the ortho aromatic hydrogens. The chemical shifts observed for the two phenyl compounds are extremely similar. A comparison of the para substituted compounds indicates identical shifts for the two para substituted methyl compounds, higher field shifts for the chlorine substituted sulfonyl fluoride but lower field shifts for the corresponding carboxylic acid substituted sulfonyl fluoride compared to the corresponding sulfonyl chlorides. 

Alkene- and arenesulphonic acids have been studied in strong or super acid media by NMR spectroscopy. Olah and coworkers64 in 1970 examined sulphonic acids in fluorosulphuric acid-antimony pentafluoride-sulphuryl chloride fluoride solution at low temperature ( — 60 °C). In S02 solution methanesulphonic acid has a chemical shift of <5 3.1 ppm for the methyl group. In the superacid medium there are two singlets at S 4.15 and 4.07, with ratio 60 40, for the methyl protons. It was suggested that this indicated the presence of two isomers, possibly 27 and 28, due to restricted rotation about the SO bond. 

Any structural feature that alters the electronic environment around a nucleus will a ect its screening constant a and lead to an alteration in its resonance frequency or chemical shift S. Consequently, to predict the chemical shift of, say, a nucleus in a particular molecular environment, the electronic wave function of the molecular system in the presence of the strong applied field must be known. For this reason it has been extremely difficult to make a priori predictions of the resonance frequencies or chemical shifts of spin l/2 nuclei [1-4]. If, for example, we wish to calculate the relative chemical shifts of the nuclei in methane and methyl fluoride, we must be able to determine accurately the electronic wave functions of both molecules in the presence of... 

Coleman et al. 2471 reported the spectra of different proportions of poly(vinylidene fluoride) PVDF and atactic poly(methyl methacrylate) PMMA. At a level of 75/25 PVDF/PMMA the blend is incompatible and the spectra of the blend can be synthesized by addition of the spectra of the pure components in the appropriate amounts. On the other hand, a blend composition of 39 61 had an infrared spectrum which could not be approximated by absorbance addition of the two pure spectra. A carbonyl band at 1718cm-1 was observed and indicates a distinct interaction involving the carbonyl groups. The spectra of the PVDF shows that a conformational change has been induced in the compatible blend but only a fraction of the PVDF is involved in the conformational change. Allara M9 250 251) cautioned that some of these spectroscopic effects in polymer blends may arise from dispersion effects in the difference spectra rather than chemical effects. Refractive index differences between the pure component and the blend can alter the band shapes and lead to frequency shifts to lower frequencies and in general the frequency shifts are to lower frequencies. 

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