1,4-Bis(2-cyanoethyl)piperazine 1,4-Piperazinedipropanenitrile 1,4-Piperazinedipropionitrile 4159-11-9 Bis(cyanoethyl)piperazine EINECS 223-992-9 NSC 13217 Piperazine-1,4-dipropiononitrile