For regression, the target values are QM computed hydricities. For binary classification, which aims to predict the site with the lowest QM computed hydricity, we assign labels as '1' for the site with the lowest hydricity and '0' for all others. A cutoff is introduced, where hydricities within +1 or +2 kcal/mol of the lowest value are also labeled '1'. Refer to section 5 in the Supporting Information for more details.