Enol-imine and keto-amine tautomerism in a series of carbohydrate-derived Schiff bases were investigated in gas, liquid, and solid-state by theoretical calculation, NMR spectroscopies, and single-crystal XRD, respectively. Two of these sugar-modified Schiff-bases derived from benzyl 2-deoxy-2-salicylideneamino-α-D-glucopyranoside (H₂L^3-tBu and H₂L^3-OMe) were synthesized and crystallized from methanol and their crystal structures determined. The results show that H₂L^3-tBu crystallizes in the enol-imine form while H₂L^3-OMe adopts the keto-amine form. The crystal packing of the latter is characterized by hydrogen bonding via the co-crystallized methanol molecules. Calculations were performed to shed light as to what parameters govern these behaviors. In this regard, eight different salicylideneamino substituted sugar-modified Schiff-bases (considering electronic and steric effects) were studied …