Fig. 1

ReactionCode structure: The ReactionCode is composed of three blocks. The first one describes the reaction center (shown in blue) and starts with ‘0:’, which corresponds to depth 0. The entire reaction center (atoms highlighted in gray) is always stored in this single layer. The block in green illustrates the atoms around the reaction center that are still kept in the product(s). This block can be composed of one or multiple layers and each layer starts with a number followed by ‘:’. The figure indicates the depth of the atoms present in this layer in relation to the reaction center. The block shown in yellow encapsulates the atoms around the reaction center which are absent in the product(s). This block can be composed of one or multiple layers and each layer starts with a letter followed by ‘:’. The figure indicates the depth of the atoms present in this layer in relation to the reaction center. (The letter A means a depth equal to one). Each layer is terminated by a ’|’ symbol and is composed of a main sub-layer that starts after the : symbol. The optional layers begin with the ‘/’ symbol. /s characterizes the stereochemistry layer. /c describes the charge layers. /i indicates the isotope layer