Q14-12 P - Organic Chemistry (Mcmurry)

Question

Show the mechanism of the acid-catalyzed polymerization of 1,3-butadiene.

Step-by-Step Solution

Answer

Step-by-Step Solution Step 1: Polymerization

Polymerization is the process of manysmall organic molecules (monomers) reacting with another small organic molecule to form the large molecule known as the polymer.

Alkene monomers are generally polymerized to bigger alkene molecules with the help of acid-catalyzed polymerization.

Step 2: Mechanism of acid-catalyzed polymerization

In the first propagation step, Alkene 1,3-butadiene acts as the monomer; when it reacts with${\text{H}}^{\text{+}}$ ion, the positive charge is transferred to the end carbon of the monomer by an attack of ${\text{H}}^{\text{+}}$ ion on the pie electrons.

In the propagation step, the cation formed attacked another monomer 1,3-butadiene, resulting in the transfer of a positive charge on another monomer carbon; the chain kept increasing as it attacked the more monomers.

In the last termination step, there is the proton donation to the counter ion resulting in the formation of the double bond at the bond end of the polymer chain.

Mechanism of acid-catalyzed polymerization