Theoretical Insight into the Coordination of Cyclic β-d-Glucose to [Al(OH)(aq)]²⁺ and [Al(OH)₂(aq)]¹⁺ Ions

Abstract

The coordination of cyclic β-D-glucose (CDG) to both [Al(OH)(aq)](2+) and [Al(OH)2(aq)](1+) ions has been theoretically investigated, using quantum chemical calculations at the PBE0/6-311++G(d,p), aug-cc-pvtz level under polarizable continuum model IEF-PCM, and molecular dynamics simulations. [Al(OH)(aq)](2+) ion prefers to form both six- and five-coordination complexes, and [Al(OH)2(aq)](+) ion to form four-coordination complex. The two kinds of oxygen atoms (on hydroxyl and ring) of CDG can coordinate to both [Al(OH)(aq)](2+) and [Al(OH)2(aq)](+) ions through single-O-ligand and double-O-ligand coordination, wherein there exists some negative charge transfer from the lone pair electron on 2p orbital of the coordinated oxygen atom to the empty 3s orbital of aluminum atom. The charge transfer from both the polarization and H-bond effects stabilizes the coordinated complex. When the CDG coordinates to both [Al(OH)(H2O)4](2+) and [Al(OH)2(H2O)2](1+) ions, the exchange of water with CDG would take place. The six-coordination complex [(ηO4,O6(2)-CDG)Al(OH)(H2O)3](2+) and the five-coordination complex [(ηO4,O6(2)-CDG)Al(OH)2(H2O)](1+) are predicted to be the thermodynamically most preferable, in which the polarization effect plays a crucial role. The molecular dynamics simulations testify the exchange of water with CDG, and then support a five-coordination complex [(ηO4,O6(2)-CDG)Al(OH)2(H2O)](1+) as the predominant form of the CDG coordination to [Al(OH)2(aq)](1+) ion.

Mechanistic Study of Glucose-to-Fructose Isomerization in Water Catalyzed by [Al(OH)2(aq)]+

“…Determination of the Active Species. In our previous computational work, 39 it was found that 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 reaction conditions, ESI-MS/MS methods were used. As shown in Figure S2, 40 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 In order to confirm whether [Al(OH)2(aq)] + species was responsible for the isomerization, HCl was added to suppress the hydrolysis of Al 3+ , which will decrease the concentration of [Al(OH)2(aq)] + species in the reaction mixtures.…”

Synergy of Lewis and Brønsted acids on catalytic hydrothermal decomposition of carbohydrates and corncob acid hydrolysis residues to 5-hydroxymethylfurfural

“…In the presence of Lewis acid catalyst (AlCl 3 ), the yield of HMF was 46%, and near absolute conversion of glucose was achieved in the system, observing the occurrence of fructose. In previous reports3132, it was found that the main active species in glucose-to-fructose isomerization reaction was most possibly the hydrolyzed aluminum species [Al(OH) 2 (aq)] + . Combined with Lewis acid and Brønsted acid, HMF yield was increased to 54.5%, and this improvement might be attributable to decreased pH (pH = 3.37 to pH = 2.50).…”

One‐Pot Deoxygenation of Fructose to Furfuryl Alcohol by Sequential Dehydration and Decarbonylation

“…[17] This indicates that the hydrolyzedA ls pecies and Pd(OAc) 2 werem ore active than HCl and Pd(OAc) 2 for the one-pot catalytic deoxygenation of fructose. [18] Additionally,t he yields of furfural and FA increased if the amount of HCl was increased, which demonstratest he ease of fructose decomposition in the presence of al arge amount of Brønsted acid. [13] We tried to removet he water that existed in the solvent and was formed during the dehydration step by adding 4 molecular sieves.…”