Spectroscopy of the Amine Group

Compound point (°C) point (°C) Compound point (°C) point (°C) 

Would you expect the hydrogens next to the heteroatom in an amine, RCH2NH2, to be more or less deshielded than those in an alcohol, RCH2OH Explain. (Hint See Exercise 21-3.) 

The NMR spectra of amines show a similar trend Carbons bound directly to nitrogen resonate at considerably lower field than do the carbon atoms in alkanes. However, as in H NMR (Exercise 21-4), nitrogen is less deshielding than oxygen. 

The rupture of the C-C bond next to nitrogen is frequently so easy that the molecular ion cannot be observed. For example, in the mass spectrum of 1-hexanamine, the molecular ion (m/z = 101) is barely visible the dominating peak corresponds to the methyleneiminium fragment [CH2=NH2] (m/z = 30). 

Spectral techniques were used to identify the molecule in Exercise 21-5 in a variety of animals. It was found that the urine of carnivores, such as lions, tigers, and raccoons, contains up to 3000 times as much of this amine as herbivores. Studies on potential prey of carnivores have shown that they have evolved highly sensitive olfactory receptors to detect the chemical and elicit an innate scurrying response. 

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