Computational Characterization of the Energetics, Structure, and Spectroscopy of Biofuel Precursors: The Case of Furfural-Acetone-Furfural

Using density functional theory, we identify the 30 low-lying structures of the furfural-acetone-furfural adduct, a valuable biofuel precursor. Focusing on the most stable species, advanced first-principles techniques are employed to provide their equilibrium geometries, the full set of their vibrational frequencies, and the pattern of their lowest singlet and triplet electronic states. A high density of isomers/conformers is found even at low energies, which complicates their identification in mixtures. The gas-phase characterization is complemented by the investigation of the water solvent effects. Our work provides the first accurate structural and spectroscopic characterization of the furfural-acetone-furfural adduct and lays the foundation for subsequent studies aiming to optimize their production, to identify them in biofuel reactors, and to investigate their reactivity.