Selective conversion of protonated d-fructose to 5-hmf and 2-fa: a nitrogen-base assisted dehydration process in the gas-phase

Understanding on a molecular level, the dehydration mechanism of sugar monomers from hemicellulose and cellulose, (e. g xylose, glucose, fructose) the main constituents of lignocellulosic biomass, to platform molecules such as 5-hydroxymethyl 2-furaldehyde (5- HMF)and 2-furaldehyde (2- FA),can offer the possibility of increasing selectivity and reaction yields in solution for the exploitation of this sustainable source. A joined approach based on mass spectrometric techniques (Electrospray Triple Quadrupole Mass Spectrometry (ESI-TQ/MS) and Electrospray Ion Trap Mass Spectrometry (ESI-QIT/MS)) together with theoretical calculations at the B3LYP/6-31 + G(d,p) level of theory was used for the study of the gas phase selective conversion of protonated D-fructose to 5-HMF and to 2-FA . Our mass spectrometric approach for the gas phase study of acid catalyzed dehydration of xylose, fructose and glucose[1-3] allowed us to structurally characterize reaction intermediates and final products and unequivocally ascertain reaction sequences. Molecular level evidences provided by our mass spectrometric approach highlighted a gas phase pathway for the selective conversion of fructose to 5-HMF through a nitrogen assisted dehydration process. Based on mass spectrometric evidences, theoretical calculations allowed a gas-phase mechanism for the selective conversion of protonated D-fructose to 5-HMF and 2-FA assisted by nitrogen-base, to be proposed. In this work the gas phase selective fructose dehydration to 5-HMF and 2 FA assisted by nitrogen bases was firstly investigated.