Lastly, we have an example of the Michael reaction, c. Here, both the experimental site of reaction and the ML predicted site of reaction match. Our ML model predicts the lowest ML predicted pK a value to be 12.5, whereas the second lowest ML predicted pK a value is 21.9 (the least substituted C-H next to a ketone). For more information, see SI -the Outliers for Reaxys section.