The right panel displays the molecular weight distribution of the acids, which primarily fall between 50 and 350 g mol , with a peak around 150 g mol -1 to 200 g mol -1 . Such molecules are small to medium-sized species, and nearly all are organic (roughly 30 species do not contain carbon). To better assess the accuracy of the ∆G o acid, gas (AH) calculations in D2A-dGgas, we sampled a set of experimental ∆G o acid, gas (AH) values from the NIST Chemistry Webbook (NIST/overlap). We used the provided names and chemical identifier information (whenever available) from the Webbook to determine acidity centers. Similar to the situation for pK a data, potential error is introduced by using a single isomeric form to represent the anion, because experimental gas-phase acidities may correspond to numerous isomers, or the exact nature of the anion is not known. We pruned the data, retaining only values with low reported uncertainties in order to establish a more reliable baseline. We also excluded carbanions due to difficulty in inferring the correct ionization sites.