Mechanistic Investigation into the Rearrangement of Lactone into Methacrylic Acid over Phosphomolybdic Acid Catalyst

The rearrangement of 3-methyl-2-oxetanone (lactone) into methacrylic acid has been explored using DFT methods. Calculations were performed for (i) intra-molecular, (ii) lactone-lactone and (iii) water and phosphomolybdic acid catalyzed conversions. The water and acid surface catalyzed route exhibited the lowest activation barrier (156 kJ mol⁻¹) of the three reaction pathways and overall is slightly endothermic (ΔH f = 37 kJ mol⁻¹).