Collision-activated dissociation studies of alkylamines formed from copper-induced dealkylation of N-alkylporphyrins.

A low-energy (5-450 eV) collision-activated dissociation (CAD) study of a series of aliphatic amines revealed that at collision energies above 200 eV, charge-site-initiated fragmentation occurs. The resulting fragment ions can be utilized in the characterization of alkyl substituents of di- and trisubstituted aliphatic amines. In the presence of Cu2+ and a suitable nucleophile, such as n-dodecylamine, N-alkyl protoporphyrins dealkylate to afford copper protoporphyrin and an alkyl-dodecylamine adduct. A CAD study of a number of alkyl-dodecylamine adducts derived from the copper-induced dealkylation of synthetic N-alkyl protoporphyrins, using charge-site-initiated fragment ions, showed that the alkyl group was trapped by the nucleophilic amine present. Subsequently this method was used to identify the alkyl group of a biologically derived N-alkyl protoporphyrin.