2-Butenoic acid, 4-(ethylamino)-4-oxo-, (2Z)- 2-Butenoic acid, 4-(ethylamino)-4-oxo-, (Z)- (9CI) 4-(Ethylamino)-4-oxoisocrotonic acid 4166-67-0 EINECS 224-021-1 N-Ethylmaleamic acid NSC 92548