13C nuclear magnetic resonance study of the protonation sequence of some linear aliphatic polyamines

Abstract

The 13C n.m.r. spectra are reported as a function of pH for 1,2-diaminoethane [en], N-(2-aminoethyl)propane-1,3-diamine [2,3-tri], 1,4,7,10-tetra-azadecane [trien], and 1,4,8,11-tetra-azaundecane [2,3,2-tet]. The previously reported amine shift parameters π and π+ are used to determine the protonation sites in the charged forms of the polyamines and the associated microscopic pKa values.