STUDY OF THE PROTONATION/DEPROTONATION SEQUENCE OF TWO POLYAMINES: BIS-[(2S)-2-PYRROLIDINYLMETHYL] ETHYLENEDIAMINE AND SPERMIDINE BY ¹H AND ¹³C NUCLEAR MAGNETIC RESONANCE

ABSTRACT

In this paper we describe the study of protonation/deprotonation of two polyamines: bis-[(2S)-2-pyrrolidinylmethyl]ethylenediamine (tetra) and spermidine (Spd). A new synthetic route was established for the synthesis of tetra, which structure was confirmed by IR, elemental analyzes, ¹H-NMR, ¹³C-NMR(Pendant) and 2D-NMR (COSY, ¹³C-¹H HETCOR and HMQC) spectra. The protonation/deprotonation sequence studies of tetra and Spd were determined by potentiometric and NMR methods. For the NMR studies, the tetra and Spd samples were dissolved in D₂O and the pD adusted with NaOD. The protonation/deprotonation sequences of tetra and Spd were determined by means of the values and the variations of the hydrogen atom and ¹³C NMR chemical shifts as a function of hydrogen atom pD. The variation of δ ¹H with pD clearly showed that the first protonation of tetra occurs at the pyrrolidine nitrogen atoms and the second protonation occurs at the ethylenediamine nitrogen atom. The analysis of the ¹³C-NMR spectra confirmed the results obtained by ¹H-NMR, as a greater chemical shift variation was observed for C-6 (5.6 ppm), as compared to C-8 (1.8 ppm). In the study with Spd, the greater chemical shift variation was observed for C-2 (6.75 ppm) and C-5 (4.95 ppm), indicating that the deprotonation occurs first at the secondary nitrogen atoms and the second and third deprotonation steps occur at the primary nitrogen atoms.

Keywords:

• bis-[(2S)-2-Pyrrolidinylmethyl]ethylenediamine
• Synthesis
• Spermidine
• Protonation/deprotonation
• ¹H and ¹³C NMR

Acknowledgments