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The experiments we have so far described have been used to study nuclei with spin I = ½ (1H, 13C, 31P). Our model compounds 1 and 2 contain two further atoms (oxygen and chlorine), which have no NMR-active isotope with spin ½. Oxygen does however have an NMR-active isotope with spin I = 5/2 but very low natural abundance (0.037%): this is 17O. Chlorine has two NMR-active isotopes: 35C1 (I = 3/2, 75...
Two-dimensional NMR? A strange concept, when we consider that all the spectra we have previously dealt with were of course plotted in two dimensions, the two axes (dimensions) being a frequency axis (horizontal, expressed in ppm rather than in Hz for reasons we have already discussed) and an intensity axis. To understand the basic idea of two-dimensional NMR (2D NMR) we should first remind ourselves...
Before starting on the problems, please refer to the worked example (see p. 64); the detailed data given in the headers of each problem should be read through carefully as they will provide vital information!
First use the molecular formula and the equation given above to calculate the number of double bond equivalents. In this case (remembering to treat bromine as equivalent to hydrogen) the value is 1. The infrared spectrum shows a band at 1641 cm−1, which probably represents the C=C bond stretch, but in this case there can only be a C=C bond present!
NMR spectroscopy is arguably the most important analytical method available today. The reasons are manifold: it is applied by chemists and physicists to gases, liquids, liquid crystals and solids (including polymers). Biochemists use it routinely for determining the structures of peptides and proteins, and it is also widely used in medicine (where it is often called MRI, Magnetic Resonance Imaging)...
The identification and structural characterisation of biological materials, obtained for example from plants, was traditionally carried out via the classical sequence involving extraction, separation, isolation and characterisation, a sequence which requires large amounts of substance and a great deal of time. Industrial problems, for example the search for small amounts of contaminants in industrial...
Hydrogen has two NMR-active nuclei: 1H, always known as “the proton” (thus “proton NMR”), making up 99.98%, and 2H, normally referred to as D for deuterium.
Dinitrato(ethylenediamine)palladium(II) has been crystallized from aqueous solution following treatment of enPdCl 2 with AgNO 3 . The en ligand is chelating and the two nitrate ligands bind monofunctionally. When brought in water, the nitrates are immediately replaced by water ligands, thus providing a convenient source of highly reactive [enPd(H 2 O) 2 ] 2+ ...
A synthesis of dihydropyrans with orthogonally protected hydroxymethyl side chains is presented in this contribution. Key steps of the synthesis are the regioselective epoxide opening using vinyl cuprate reagents, selective protection of primary alcohols and ring closing metathesis. A strategy based on the intermediate formation of a rigid bicyclic acetal turned out to be unsuccessful due to the unexpected...
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