John 17:5

Greek πρὸ τοῦ τὸν κόσμον εἶναι παρὰ σοί. The Greek literal here is "in front/before the the world to be beside you." τὸν κόσμον "the world" is in the accusative case. It is the object therefore of the verb εἶναι "to be" as seen in Matthew 16:13 εἶναι τὸν Υἱὸν "to be the son" which is also in the accusative case. The two definite articles τοῦ τὸν "the the" are genitive and accusative respectively. To translate this phrase as "of the world" disregards the accusative case.