A Theoretical Study of the Fragmentation Mechanism of Deprotonated Alanine (DFT)

Abstract

In this paper, density functional theory (DFT) was applied to study the isomerization process and fragmentation mechanism of deprotonated alanine ions ([β-Ala–H]–) at B3LYP/6-311++G (2df, 2pd) level. Deprotonated α-alanine ions generally have lower energies than deprotonated β-alanine ions, and 1a2 is the most stable structure. In the isomerization process, the reaction barrier (ΔG≠) required for hydrogen transfer is the highest, that the pathway of NH3- loss reaction to the product p3 is the only forward spontaneous reaction in thermo dynamics and NH3-loss reaction is also easier than H2O-loss reaction in kinetics. Meanwhile, the effect of temperature on the optimal H2O- and NH3-loss reaction paths of the deprotonated α- and β-alanine ions were investigated, and the results showed that temperature had little effect on H2O- and NH3-loss reactions. In addition, different calculation methods and focus analysis of the basis group were investigated, and the results show that B3LYP/6-311++G (2df, 2pd) level is suitable for this study.