$BrC6H4CH2Br$ +$NaOH$ loãng nóng \rightarrow $BrC6H4CH2OH$ +$NaBr$ $BrC6H4CH2Br$ +3 $NaOH$ đặc nóng \rightarrow $ONaC6H4CH2OH$ + +2$NaBr$ + $H2O$
$CH3CH2Br$ + $Mg$ \rightarrow $CH3CH2MgBr$
$CH3CH2MgBr$ + $CO2$ \rightarrow $CH3CH2COOMgBr$
$CH3CH2COOMgBr$ + $HBr$ \rightarrow $CH3CH2COOH$ + $MgBr_2$