For ammonia, the primary reaction path found with meta-MD as the first step is nucleophilic attack at the β-carbon of MA to form intermediate 13 (Figure ). Another major reaction is transfer of a proton from ammonia to oxygen simultaneously with the nucleophilic attack forming intermediate 16. For phosphine, we see another primary reaction path for the first step of meta-MD generated products which is the addition of phoshine to the double bond forming intermediate 12 (Figure ). While the second most observed reaction is nucleophilic attack of phosphine to the β-carbon of MA forming intermediate 25, the Gibbs free energy at 27 kcal/mol is much higher and in fact very close to our cutoff of 30 kcal/mol. In ammonia's case we do find the next step of the MBH reaction when reacting intermediate 13 with pNBA forming intermediate 209. However, when trying to optimize this intermediate at the DFT level, we observe a proton transfer between nitrogen and oxygen forming intermediate 138 (Figure ). Intermediate 430 is found within the same iteration as a tautomer to intermediate 138. For phosphine on the other hand we observe another intermediate where a five-membered ring is formed from phosphor and oxygen binding (intermediate 151) which is possible due to phosphors ability to form 5 bonds. We do find the expected MBH intermediate (intermediate 371) in the next meta-MD iteration and with it intermediate 1752 from a proton transfer reaction which is the equivalent to intermediate 430 for ammonia. Thus, the reason we are not observing the MBH product for phosphine is that the extra intermediate observed on the path (intermediate 151) means that it would take another, fourth, iteration of our reaction discovery method to get there.