Having established a qualitative correlation between reactivity and proton affinity computed by GFN1-xTB/methanol, we computed the highest proton affinity of the most stable tautomer for the 535 molecules in our data set. The results (5c) show that 92% of the molecules have proton affinities in the range 70-100 kcal/mol -a range similar to that found for most of the reactive (ortho-para directing) molecules shown in 5a. Molecules with higher and lower proton affinities are thus deemed unusually high and low reactivity, respectively. RegioSQM20 therefore uses these cutoffs to classify a molecule as having low, medium, or high reactivity and displays this information in the output (Fig. ).