Nuclear magnetic resonance spectra, hydrogenation

Mathematical models are the link between what is observed experimentally and what is thought to occur at the molecular level. In physical sciences, such as chemistry, there is a direct correspondence between the experimental observation and the molecular world (i.e., a nuclear magnetic resonance spectrum directly reflects the interaction of hydrogen atoms on a molecule). In pharmacology the observations are much more indirect, leaving a much wider gap between the physical chemistry involved in drug-receptor interaction and what the cell does in response to those interactions (through the cellular veil ). Hence, models become uniquely important. 

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. 

Eq. 47). A band in the nuclear magnetic resonance spectrum corresponding to the methylene hydrogens of the aziridinium ring provided particularly valuable evidence for the structure of the product. The method seems to be very general, and has been utilized for the pie-... 

The presence of a carboxylic acid group is indicated by strong infrared absorption in the region of 1720 cm-1 (C=0 str.) and broad absorption between 3400 cm-1 and 2500 cm-1 (OH str.) in the nuclear magnetic resonance spectrum the acidic hydrogen (replaceable by D20) will appear at very low field (3 10-13). 

Primary amines may be readily distinguished from secondary and tertiary analogues by the presence of two absorption bands in the infrared spectrum between 3320 and 3500 cm-1 (symmetric and antisymmetric NH str.). Secondary amines exhibit a single absorption band at about 3350 cm-1 (NH str.). In both cases deformation modes for the NH bond appear at about 1600 cm-1. There is no satisfactory absorption to allow a definitive characterisation in the case of tertiary amines. In the nuclear magnetic resonance spectrum of primary and secondary amines, the nitrogen-bound hydrogens are recognisable by their replaceability on the addition of deuterium oxide. 

C—H str.). In the nuclear magnetic resonance spectrum of an aldehyde a low-field signal for the aldehydic hydrogen (S 9-10) is characteristic. 

Fig. 5. H-Nuclear magnetic resonance spectrum of ketotifen hydrogen fumarate with 2.5 1 0. Instrument Jeol FX-100 at 100 mHz. 

The proton nuclear magnetic resonance spectrum of the thorium hydride shows a resonance at 6 0.90 due to the hydride. The source of the hydride has been shown to be one of the hydrogen atoms of tetrahydrofuran since conducting the reaction in perdeuterotetrahydrofuran yields the monodeuteride. Tetrahydrofuran is essential since boiling C1M[N(SiMe3)2]3 with NaN(SiMe3)2 in benzene, toluene, isooctane, or diethyl ether results in isolation of unreacted C1M[N(SiMe3)2]3 ... 

Attempts to prepare esterified glycals by the reduction of glycofuranosly halides with zinc in acetic acid failed, because of the reactivity of this class of compound (see p. 92). When, however, 3,5-di-0-benzoyl-2-0-(p-nitrophenylsulfonyl)-/3-D-ribofuranosyl bromide (8) in acetone is treated at 5° with sodium iodide, a facile elimination takes place and 3,5-di-O-benzoyl-1,2-dideoxy-D-er2/i/iro-pent-l-enofuranose (9) is obtained crystalline, in 72% yield. The product was characterized by identifying its hydrogenation product as the known l,4-anhydro-3,5-di-0-benzoyl-2-deoxy-D-er2/nuclear magnetic resonance spectrum, which showed clearly that the glycal structure was present. 

The nuclear magnetic resonance spectrum shows that there is probably only one of the two possible isomers present, but the evidence at the moment cannot show whether the tertiary hydrogens are exo or endo, although other considerations favor endo hydrogens. 

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