1 CH2=CH2+Br2----->CH2BrCH2Br
2 CH2BrCH2Br+2NaOH------>CH2(OH)CH2OH+2NaBr
3 CH2(OH)CH2OH+O2----->OHC-CHO+2H2O
4 OHC-CHO +O2------->HOOC-COOH
5 CH2(OH)CH2OH+HOOC-COOH----浓H2SO4--->C4H4O4+2H2O