Elucidating Reaction Mechanisms and Solvent Effects in the Formation of Bio-Sourced Molecules

The development of sustainable chemical processes based on renewable carbon sources requires selective transformation strategies for structurally complex biomass-derived molecules. However, these substrates often participate in dense reaction networks involving competing pathways and transient intermediates. This thesis investigates the mechanistic foundations of selected biomass-derived reaction systems, with emphasis on understanding how reaction environment governs selectivity.

Advanced nuclear magnetic resonance (NMR) spectroscopy was employed as the primary analytical platform. Thermal time-resolved in situ NMR, isotope labeling, hyperpolarized dissolution dynamic nuclear polarization (dDNP) NMR, and kinetic modeling were integrated to monitor reaction progress, identify intermediates, and validate mechanistic hypotheses under operational conditions.

In the acidic oxidation of furfural, in situ NMR experiments revealed a complex network consistent with Baeyer–Villiger-type oxidation pathways. Multiple intermediates were detected and structurally validated, enabling development of a kinetic model that reproduced experimental concentration–time profiles. dDNP-NMR experiments provided experimental observation of a transient formyl ester intermediate. Variation of acid concentration and additive composition demonstrated that product selectivity between maleic and fumaric acid is strongly governed by proton activity and electrostatic stabilization in solution.

The base-catalyzed oxidative degradation of saccharides to formic acid was studied using ¹³C isotope labeling to resolve competition between C–C bond cleavage and aldose–ketose isomerization pathways. High selectivity toward formic acid was achieved under mild aqueous conditions when oxidant and base concentrations were optimized. Extension to di- and oligosaccharides showed that mechanistic accessibility of reactive sites significantly influences overall conversion efficiency.

Mechanistic investigations of polyfunctionalized furan formation from aldoses further demonstrated how catalytic mode and solvent environment alter pathway selection under both Brønsted base and Lewis acid catalysis. Complementary studies on solvent effects, zeolite-assisted oxidation, and related furan systems reinforced the central role of reaction environment in governing reactivity and selectivity across diverse biomass-derived transformations.

Across all systems examined, solvent properties, acidity, and catalytic mode emerged as critical parameters influencing kinetic behavior and pathway bifurcation. The combined spectroscopic and modeling approach enabled direct observation of transient species and quantitative validation of reaction mechanisms, contributing to a mechanistic framework for rational development of selective transformations in biomass valorization.