Towards a de-novo route to drop-in biobased 3-methyl phthalic anhydride, a first principles computational study

Abstract

The search for functional replacements of fossil-based fuels and chemical building blocks has produced promising sugar-based chemicals. Among these is phthalic acid. An experimental procedure for the zeolite-catalyzed synthesis of 3-methyl phthalic anhydride, which was performed in our group, serves as the basis for a modeling investigation. Prior reported observations were used to design a computational DFT workflow. With a systematic application of the model Brønsted reaction a partial reaction network is produced. Inspection of this network yields observations on both thermodynamic and kinetic descriptions of the reaction. The model workflow gains validity by being able to rediscover intermediates that were assigned experimentally. The findings indicate that a previously ‘unexpected’ lactone intermediate results directly from a 1,3-substitution pattern on the reactant. This lactone is instrumental in determining the product composition and selectivity towards a phthalic anhydride precursor. The modular workflow can serve as a platform for future mechanistic analysis in similar reactions as well.