下列反应各以何种机理为主? 1. CH3CH2CHBrCH2CH3 CH3CH== CHCH2CH3 + (88/%) (12/%) 2. C6H5CHClCH3 C6H5CH(OH)CH3 (90/%外消旋化) 3. C6H13CHBrCH3 C6H13CH(OH)CH3 (30/%外消旋化)