Nuclear magnetic resonance spectra oxidation product

Tris(dimethylamino)arsine (d2o 1.1248 nd 1.4848)3 is a colorless liquid which is readily hydrolyzed to form arsenic (III) oxide and dimethylamine when brought into contact with water. The compound is soluble in ethers and hydrocarbons. The product is at least 99.5% pure (with respect to hydrogen-containing impurities) as evidenced by the single sharp peak at —2.533 p.p.m. (relative to tetramethylsilane) seen in the proton nuclear magnetic resonance spectrum of the neat liquid. 

In alkaline solution, D-arofetno-hexulose phenylosazone is oxidized by atmospheric oxygen to give a product which, from chemical degradative evidence, was assigned the revised (but still inaccurate) structure (70). Although the nuclear magnetic resonance spectrum of the derived tri-... 

Other methods of identification include the customary preparation of derivatives, comparisons with authentic substances whenever possible, and periodate oxidation. Lately, the application of nuclear magnetic resonance spectroscopy has provided an elegant approach to the elucidation of structures and stereochemistry of various deoxy sugars (18). Microcell techniques can provide a spectrum on 5-6 mg. of sample. The practicing chemist is frequently confronted with the problem of having on hand a few milligrams of a product whose structure is unknown. It is especially in such instances that a full appreciation of the functions of mass spectrometry can be developed. 

Some of the important differences in the nuclear magnetic resonance spectra of the /3-n-furanose form in various solvents are shown in Table I. As expected, the chemical shifts are somewhat altered on changing the solvent however, new bands appear with pyridine. In methyl sulfoxide, the mutarotation is very slow, and only one form is seen soon after dissolution. In anhydrous pyridine, the mutarotation is a little faster, so that, in a few minutes, the a- and /S-n-furanose forms are present in equal amounts. With the addition of deuterium oxide, equilibrium between the three forms is rapidly reached. This last spectrum is essentially the same as that of the crude product mentioned earlier. The small values for Jz 4 indicate that all three forms are in fixed conformations and are, therefore, not acyclic. The spectrum of the a-D-pyranose form is closely related to that of (24). The two furanose forms show, overall, a similar spectrum, except that the proton at C-1 of the )3-d anomer shows a relatively large coupling, J = 3.25, of unknown origin. The spectra of many five-membered heterocyclic compounds are anomalous, and not yet fuUy understood. 

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