How can you get propane and butane if given the following substances: methane, metallic sodium, chlorine?

Given: CH4, Na, Cl2;
Get: C3H8, C4H10;
To solve, we write down the chain of transformations:
CH4 – CH3Cl – C2H6 – C4H10 \ C3H8;
Let’s compose the equations:
CH4 + Cl2 = CH3Cl + HCl;
2CH3Cl + 2Na = C2H5 + 2NaCl;
C2H6 + Cl2 = C2H5Cl + HCl – ethane chloride is released;
C2H5Cl + 2Na + CH3Cl = C3H8 + 2NaCl – propane was obtained;
2С2Н5Cl + 2Na = C4H10 + 2NaCl – butane was formed during the Wurtz reaction;
These reactions show the possibility of obtaining saturated hydrocarbons through the Wurtz reaction, which allows the lengthening of the hydrocarbon chain.