CH2=CH-CH=CH2+Br2 = CH2(Br)-CH=CH-CH2(Br)  1,4-дибромбутен-2

  CH2Br – CH = CH – CH2Br – NaOH (водн)  =  CH2OH – CH = CH – CH2OH

CH2OH – CH = CH – CH2OH+H2-Pt = CH2OH-CH2-CH2-CH2OH

CH2OH-CH2-CH2-CH2OH + KMnO4 + H2SO4  =  HOOC-CH2-CH2-COOH + MnSO4 + K2SO4 + H2O