| Popis: |
Most biochemical processes are energetically uphill, requiring a constant supply of energy to sustain them. These processes are described as "dissipative". Species formed by dissipative self-assembly exhibit unique life-like properties such as temporal control and mechanisms of self-replication, self-healing, and adaptation that are simply not feasible at equilibrium. The focus of my dissertation was on the use of N-(3-dimethylaminopropyl)-N-ethylcarbodiimide hydrochloride (EDC), a common reagent, to "power" carboxylic acids out-of-equilibrium by forming the corresponding transient carboxylic acid anhydrides, which subsequently revert back to the original acid precursors via hydrolysis.While the two reactions making up our system were well-known independently, we lacked a good understanding of the mechanistic details of the coupled system. Although carbodiimide fueled dissipative chemical reactions are now well established with the recent publications from the Boekhoven group and our group, we still lacked a fundamental understanding of the mechanistic details, for example, structural effects on this chemistry. Hence, in Chapter 2 we investigated reactions of simple benzoic acid derivatives with EDC under typical reaction conditions and found that structural effects play a significant role in the assembly process. Notably in this study, we took first steps to demonstrate that the kinetic modeling could be used to predict the lifetime, yields/efficiencies, and maximum concentrations of the transient anhydride species via simulations of the systems under numerous starting conditions.To demonstrate the utility of this carbodiimide fueled chemistry, in Chapter 3 we envisioned that intramolecular anhydride formation in oligo(ethylene glycol) diacids would result in macrocycles analogous to crown ethers. These represent perhaps the simplest examples of transiently formed nonequilibrium supramolecular hosts known to date. We investigated the effect of guest cations on anhydride formation and found that the presence of `matched’ cations gave diminished yields in a counterintuitive way (a "negative templation effect"). Chapter 4 focuses on probing the negative templation phenomenon with newly designed mono- and diacid precursors. Mechanistic simulations allowed us to calculate yields for the macrocyclic anhydride. We noticed a templation effect in the presence of matched guest cation(s) that is supported by the more efficient cyclization to produce more macrocycle compared to the acyclic oligomer formation. This probably supports pre-coordination of the guest cations to the activated EDC intermediate prior to the anhydride formation. |
