CH3 3.制备 CH:CH,CH,CHCOOH CHCCHCOOE NaOEt CH,I NaOEt CH:CH,CH2Br EtOH EtOH CH3 CHCC-COOEt 酸式分解ACH,CH,CH,CHC0OH+CH,COOH OH(浓)H CH2CH2CH3 U