Thesis (Ph.D.)--Chulalongkorn University, 2015

In this thesis, the new insights of the Biginelli reaction, and the glucose transformation to 5-hydroxymethylfurfural have been provided. The obtained most favorable pathways have been purposed without prejudice. Also, the solvent effect in each reaction has been considered. The artificial force induced reaction (AFIR) method was applied to investigate systematically all possible multi-component pathways for the Biginelli reaction mechanism. Among all possible pathways, the most favorable one starts from the C-N bond formation between urea and benzaldehyde molecules, and follows by the nucleophilic addition of ethyl acetoacetate molecule. Surprisingly, an extra urea molecule is catalyzing the reaction nearly every step. Therefore, the Biginelli reaction is a urea-catalyzed multicomponent reaction. The reaction was found identical in ethanol and toluene. For glucose transformation to 5-hydroxymethylfurfural (HMF), RISM-SCF-SEDD method coupled with ab initio electronic structure theory, namely coupled cluster single, double, and perturbative triple excitation (CCSD(T)) has been employed to consider the reaction in both ionic liquid (IL) and water. We found that glucose isomerization in water favored the cyclic mechanism, while open chain mechanism is more favorable in ILs. Besides, the reasonable pathway of the transformation of fructose into HMF is the cyclic mechanism in both IL and water. The decomposition of free energies and radial distribution functions (RDFs) of solute-solvent that are operated by RISM-SCF-SEDD was utilized to clarify the solvent effects of IL.