1. A computer based method for identifying at least one pair of similar chemical reactions between a plurality of reactions each related to preparation of at least one product from at least one reagent, the method comprising: generating for each reaction a structural representation involving dynamic and conventional bonds; generating based on the structural representation, for each reaction, a set of fragment descriptors of a predetermined length comprising the dynamic bonds and a corresponding descriptor vector; calculating similarity indices between descriptor vectors of the plurality of reactions; comparing the similarity indices to identify at least one pair of similar reactions; generating for a query reaction a structural representation involving dynamic and conventional bonds; generating based on the structural representation generated for the query reaction a query descriptor vector; calculating similarity indices between the query descriptor vector and other descriptor vectors corresponding to reactions listed in a database; and comparing the similarity indices between the query descriptor vector and other descriptor vectors to identify at least one reaction similar to the query reaction in the database.