Relationships between DFT/RRKM Branching Ratios of the Complementary Fragment Ions [C5H5O]+ and [M – C5H5O]+ and Relative Abundances in the EI Mass Spectrum of N-(2-Furylmethyl)aniline

The energy-dependent branching ratios of the complementary fragment ions [C5H5O]+ and [HC6H4NH]+ ([M – C5H5O]+), originating from the N-(2-furylmethyl)aniline molecular ion, [HC6H4NH–C5H5O]+•, were obtained from Rice–Ramsperger–Kassel–Marcus (RRKM) rate calculations based on density functional theory (DFT) energy profiles. The UB3LYP/6-311G+(3df,2p)//UB3LYP/6-31G(d) level of theory was used to model the competitive reaction mechanisms by which the molecular ion can be fragmented. Initially, eight pairs of products were taken into account, corresponding to the combination of two isomeric structures for each fragment ion and the concomitant radicals, which can be formed by direct dissociations or through some isomerization-fragmentation pathways. A great deal of the obtained pathways was discarded by looking over the kinetic barrier heights and the individual RRKM rate coefficients calculated for all the steps. This way, the potential energy profiles were simplified to only three reaction channels, two path...