(E)-2-Butenoic acid (E)-Crotonic acid 107-93-7 2-Butenoic acid, (E)- (9CI) 4-02-00-01498 (Beilstein Handbook Reference) BRN 1719943 Crotonic acid Crotonic acid, (E)- EINECS 203-533-9 NSC 8751 trans-2-Butenoic acid trans-Crotonic acid