The mechanisms and molecular properties about isomerization of resin acids, synthesis of acrylopimaric acid based on density functional theory calculation

Acrylopimaric acid is considered a possible substitute for petroleum-based polymeric monomers. Resin acids were isomerized to form levopimaric acid(4), which reacted with acrylic acid to synthesize isomers of acrylopimaric acid. Density functional theory calculations were carried out to investigate the reaction mechanisms with seven reaction paths. In terms of dynamics, the energy barrier in the isomerization of palustric acid(2) to levopimaric acid(4) was the lowest, whereas the highest energy barrier was the isomerization of neoabietic acid(3) to levopimaric acid(4). The addition reaction of levopimaric acid(4) and acrylic acid(5) to acrylopimaric acid c(8) was the optimal reaction path dynamically. However, the energy of acrylopimaric acid c(8) was higher than that of acrylopimaric acid d(9). Highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO-LUMO) were analyzed for eight kinds of molecules. For acylpyimaric acid, the nonplanar six-memed ring and the C-C double bonds were easily attacked by nucleophile, whereas the nonplanar six-memed ring and the carboxyl group are easily reacted with electrophiles. The electrostatic surface potential were analyzed for molecules.