2-Butenoic acid, 2-propenyl ester 2-Propenyl 2-butenoate 20474-93-5 AI3-24212 Allyl 2-butenoate Allyl beta-methylacrylate Allyl crotonate Allyl trans-2-butenoate Crotonic acid, allyl ester EINECS 243-845-2