Experimental Determination of the Acidic Dissociation Constant and Gibbs Free Energy of Dissociation for Deuteron-Selected Acetic Acid

A deuteron-selected acid is one in which the acidic proton (1H+) has been replaced with a deuteron (2H+ or D+). Deuterium selection has seen a recent rise in popularity within the pharmaceutical industry for its desirable effects on prescription medications, wherein the selection of deuterium causes slower drug metabolic rates without reduction of treatment effectiveness; it may also reduce toxicity through altered metabolic pathways. This delayed metabolic rate is caused by the kinetic isotope effect, a physical chemistry phenomenon in which a large increase in the relative mass of an isotope causes bond dissociation (splitting) to become less kinetically/energetically favorable. The goal of this research was to determine the relative energetic favorability of deuteron-selected acetic acid via experimental determination of the Gibbs Free Energy (ΔG) of dissociation, a thermodynamic value which assesses the energetic favorability of acidic dissociation at standard conditions. This involved utilizing a modified titration technique to determine the equilibrium constants (Ka) for both acids, which were then interpolated to calculate Gibbs Free Energy of dissociation for the protonated and deuterated form of each acid for comparative thermodynamic profiling