Some demos to try: Start the program with: $ maprxn "CBr>>CI" Enter these reactions: CCCC(Br)C=C>>C=CC(I)CCC BrC(C)CCCBr>>BrC(C)CCCI Start the program with: $ maprxn "O=CO.OC>>O=COC.O" $ maprxn "O=CO.OC>>O=COC" Enter these reactions: CCCC(=O)O.OCCN(C)C>>CCCC(=O)OCCN(C)C CCCC(=O)O.OCCN(C)C>>CCCC(=O)OCCN(C)C.O