Hydrogen bond induced acidic liquids for efficient biodiesel production

In chemical engineering, the Fischer-Speier esterification shows incredible value for biofuel production. However, the transformation suffers from challenges including necessary catalysts that cause corrosion issues in addition to a complex synthesis. Herein, we report a green acidic liquid, [N,N,N-tris(propanesulfonic)aniline][ethanol](3), which is induced by hydrogen bonding interactions between a hydrogen bond acceptor (HBA) of [N,N,N-tris(propanesulfonic)aniline] and three hydrogen bond donators (HBD) of ethanol, through a one-step reaction. This liquid demonstrates strong Bronsted acidity and hydrogen bond networking to mimic ionic liquids (ILs) or deep-eutectic solvents (DESs). Even under mild conditions, biodiesel was produced with 97.65% of esterification conversion. Exploiting distinguished molecular geometry with a singular methodology, made possible by contributions from HBD, allows for a further reaction of 1,3-propanesulfonate with positively charged amines. This discovery is feasible with a wide range of HBDs as a solvent resulting more commercially accessible products owing to a much greener synthesis when compared with ILs and DESs.