Protons, in NMR

Boryl-borate tautomerism This type of tautomerism is observed for boryloxyalkylphosphines (101), (102) possessing a hydroxyalkyl group and electron-acceptor substituents at the a-carbon atom [Eq. (88)] (851ZV1102 90IZV1133). Mutual transformations take place rapidly and the equivalency of methyne protons in NMR spectra serves as evidence of tautomerism. In the crystalline state these compounds exist in form A. The considerable influence of the nature of the solvent (-4 ppm in DMFA - 10 ppm in C6H6) on the position of the signal in the MP NMR spectrum provides evidence in favor of tautomerism. 

Problem 8. Explain the abnormally large shift of aldehydic proton in nmr spectra. 

H. C. Siebert M. Frank C. W. Lieth J. Jimenez-Barbero H. J. Gabius, Detection of Hydroxyl Protons. In NMR Spectroscopy of Glycoconjugates J. Jimenez-Barbero, T. Peters, Eds. Wiley-VCH Weinheim, 2003. 

Since has an odd mass number, nuclei absorb in the NMR and, in many ways, these nuclei behave similarly to protons in NMR spectroscopy. With this in mind, explain why the NMR spectrum of methyl dimethylphosphonate, CH3PO(OCHa)2, consists of two doublets at 1.5 and 3.7 ppm. 

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