Dissertation Defence: Elucidating the “On Water” Mechanism in Accelerated Reactions in Water

Eduardo Alejandro Romero Montalvo, supervised by Dr. Gino DiLabio, will defend their dissertation titled “Elucidating the “On Water” Mechanism in Accelerated Reactions in Water” in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Chemistry.

An abstract for Eduardo Alejandro Romero Montalvo’s dissertation is included below.

Examinations are open to all members of the campus community as well as the general public. Please email gino.dilabio@ubc.ca to receive the Zoom link for this defence.

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ABSTRACT

Water as a reaction medium in organic reactions has potential applications in different areas of chemistry. Consequently, aqueous organic chemistry has increasingly become relevant in the past few decades; one of these types of reactions, and the main topic of this thesis, is the “on water” reaction. This reaction involves the increased rate of reactions of selected organic reactions when they occur in the presence of an organic aqueous interface; such an increase in the kinetics of the reaction is relative to the same reaction in solventless or organic solvent conditions. Over the years, some models based on hydrogen bonding, proton transfer and dipole moment have been proposed. Still, there has yet to be a general agreement on the molecular origin of this phenomenon. In this thesis, we explored, through computational methods, the mechanism driving this unusual reactivity. It was found that the accelerated effect observed in “on water” reactions arises from a combination of different effects: hydrogen bonding at the interface stabilizes transition states with respect to pre-reaction complexes, and strong electric fields near the water-oil interface have a dominant effect on the reduction of energy barriers associated with “on water” reactions. Based on these findings, we propose a new mechanism for “on water” reactions. In addition, we present an explanation of the origin of the kinetic isotope effect that “on water” reactions display based on the difference in the macroscopic physical properties between D2 O and H2 O (kH /kD). This thesis offers insights into the still poorly understood chemistry of water in heterogeneous conditions; it provides a rationale for understanding chemical processes occurring near confined or interfacial water. The insights found in this thesis are relevant to other fields of chemistry, such as green chemistry, biochemistry, organic chemistry and atmospheric chemistry.