On the mechanism of protonation of triamines

Abstract

The protonation behaviour of several triamines having the general formula H₂N[CH₂]_mNH[CH₂]_nNH₂ with m⩽n has been studied by ¹³C and ¹H n.m.r. techniques. In all cases, in the first two protonation steps, only primary amino-groups are involved. The protonation of the secondary amino-group starts only after the protonation of the primary ones is complete.

In the case of symmetrical triamines, in the first step, the proton is shared by the two primary nitrogens to an equal extent. Unsymmetrical triamines having m < 3 are initially protonated on the primary nitrogen atom attached to the longer aliphatic chain. However the unsymmetrical triamine spermidine, having m= 3 and n= 4. behaves like the symmetrical ones.