Theoretical study of the degradation mechanisms of substituted phenyltrimethylammonium cations

Degradation mechanisms of substituted phenyltrimethylammonium cations were investigated through density functional theory (DFT) calculations performed at the B3LYP/6-311++G (2d, p) level. Several substituents and their positions on the benzene ring were changed in order to explore the relation between the orientation effect and the stability of the substituted phenyltrimethylammonium cations. The results of the DFT calculations indicated that the calculated energy barriers are raised when the electron-donating substituents are at the ortho and para positions of the benzene ring. Specifically, the calculations showed that the double-(CH 3 ) 2 N-substituted phenylTMA+ is more stable than the double-(CH 3 ) 2 N-substituted benzylTMA+. The highest increase in ΔG ≠ was 3.7 kcal/mol and resulted from the triple (CH 3 ) 2 N-substitution of phenylTMA+. These results elucidate the effects of substituents on the degradation of model cations and provide a reference for their potential use in anion-exchange membranes.