| Popis: |
The infrared spectra of primary alkylamines largely belong to one of two different types as found out by a systematic data search. This search was motivated by observing before an intriguing spectral pattern (type-I) in our studies of octadecylamine, with only one ν NH band, and, besides, the signature for ammonium groups. This particular type-I spectrum occurs whenever amines are determined to adopt a solid state, that is, as a rule, in the long-chain analogs. The other, so to speak “classical” type-II of amine spectra arising from fluid-phase or very diluted samples shows two ν NH bands and no ammonium markers, and exclusively this pattern is given in the current textbooks for generally representing primary amine. Concerning the “new” type-I amine spectra found by ourselves for octadecylamine and shown also by others, a clear phenomenological description is hitherto missing, not to mention a relevant interpretation. Here, we characterize these spectra for the first time in detail and propose that the chemical compound underlying them actually is ammonium amide. The relevant far-reaching implications involve then logically a proton transfer to proceed from one amino group to the other. Reasonably presumable driving forces for this self-dissociation reaction are discussed. |
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