(-СН2-С(СН3)=СН-СН2-)n думаю логика понятна
СH4 + Cl2=CH3Cl + HCl
2CH3Cl + 2Na = C2H6 + 2NaCl
C2H6 + Cl2 = C2H5Cl + HCl
C2H5Cl + CH3Cl + 2Na = C3H8 + 2NaCl
C3H8=C3H6 + H2
C3H6 + Cl2 = C3H6Cl2
C3H6Cl2 + 2KOH = 2KCl + 2H2O + C3H4
C3H4 + H2O (Hg2+)=Н3С-СО-СН3