Mild decarboxylation of neat muconic acid to levulinic acid: a combined experimental and computational mechanistic study

Abstract

Levulinic acid (LA) is a key platform molecule with current applications in the synthesis of several commodity chemicals, including amino-levulinic acid, succinic acid, and valerolactone. In contrast to existing petroleum-based synthesis pathway, biomass-derived cis–cis-muconic acid (MA) offers a sustainable route to synthesize LA. Here, we show the complete decarboxylation of neat MA to LA without solvent at atmospheric pressure and mild temperature. In a series of sulfuric acid catalyzed experiments, we used a suite of one and two-dimensional NMR techniques along with gas chromatography-mass spectrometry (GCMS) analysis and density functional theory (DFT) calculations to elucidate the intermediates involved in LA synthesis. Experimental kinetic studies revealed rate constants for the consumption of MA and the formation of LA, with activation energies calculated to be 16.10 kJ mol⁻¹ and 158.18 kJ mol⁻¹, respectively.