Nuclear magnetic resonance spectra amines

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. 

Certain functional groups in a molecule (e.g., hydroxyl, carbonyl, and amine) absorb IR radiation and exhibit absorption bands at characteristic frequencies regions regardless of the structure of the rest of the molecule. These bands are termed group frequencies. They are predictable and allow the analyst to deduce important structural information about an unknown molecule. An IR spectrum can be rapidly recorded for any phase, i.e., solid, liquid, or vapor. By coupling IR spectroscopy with other analytical techniques such as nuclear magnetic resonance (NMR)... 

Apart from giving information about solvent participation, the nuclear magnetic resonance (n.m.r.) spectrum can reveal other features of the reaction mechanism as well. The reason for this is that the spectrum often consists of several resonances the independent analysis of which gives different and complementary kinetic information. Thus, for asymmetrically substituted amines, it is possible to measure the rate of Walden inversion as well as the rate of proton exchange [11,12]. In other cases it is possible to compare the rate of proton exchange (as measured by n.m.r.) with that of proton transfer (as measured by relaxation spectrometry), thus evaluating statistical factors in proton exchange [13]. 

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