Once the bonds were computed at each timestep, reactions could be extracted by finding bond rearrangements in the MD simulation. The reactions were represented using a formalism close to the "atomic features" described in previous work with some adjustments that are recounted here. The "atomic features" framework describes reactions based on the atoms surrounding the reactive site. Each atom is featurized by its type (carbon or hydrogen), its number of carbon neighbors and its number of hydrogen neighbors. Between two timesteps, several pairs of atoms can switch from bonded to unbonded or inversely; in this case, one or several reactions occur. When these reactions occur, they are described by the features of the atoms involved in the reaction and the bonds that are changed. We chose here to only keep the reactions that involve 2 or 3 atoms and discard reactions with 4 or more atoms. This assumption was made because the reactions with 4 or more atoms represented less 0.2% of the total reactions and increased significantly the KMC simulation run time. Accounting for reactions with 3 atoms is the main difference from our previous work where reactions were only considered to be the breaking or the creation of a single bond. This modification was made to be closer to the definition of an elementary reaction which is the rearrangement of bonds occurring within one collision and which authorizes more than 2 atoms to be involved in a reaction. This "atomic features" framework is compared in detail in Ref. with the more traditional approach of considering reactions between molecules, called "molecular features" framework. It is shown that the "atomic features" framework is more appropriate to describe reactions of long carbon chains, needs less reactions to describe a system, and can learn faster than the "molecular features" framework.