Understanding the Effect of Acid Strength on the Alkane-Alkoxide Hydride Transfer Reaction over Solid Acid Catalysts: Insights from Density Functional Theory

Abstract

Hydride transfer as the key step in the alkylation reaction harbors burgeoning research interest. Herein, the influence of acid strength on hydride transfer was investigated via density functional theory. Based on energetic analysis, increasing acid strength can stabilize the carbenium ion and destabilize alkoxide species, resulting in significant improvement of hydride transfer performance. Notably, the hydride transfer reaction cannot occur at a weak acid site owing to difficulty in forming a stable H-shared intermediate, which perfectly coincides with experiments. More interestingly, the changing extent of energy for intermediates and transition states correlates well with the ionic character at various acid strengths. A stronger ionic character leads to a larger changing extent of energy. Therefore, the changing trends of activation energy barriers to acid strength can be predicated by comparing the strength of ionic character between reactants and transition states. The results are of referential significance to the development of highly efficient catalysts for C4 alkylation.