The synthesis of polypropylene from propylene monomer involves a process called polymerization. The most common method for producing polypropylene is through Ziegler-Natta polymerization, which uses a catalyst system composed of a transition metal usually titanium and an organoaluminum compound. Here is the step-by-step reaction mechanism for the synthesis of polypropylene from propylene monomer using Ziegler-Natta polymerization:1. Catalyst activation: The titanium-based catalyst is activated by reacting with the organoaluminum compound, which is usually an alkyl aluminum compound like triethylaluminum TEAl . This reaction generates a highly reactive, coordinatively unsaturated titanium species that can initiate the polymerization.2. Monomer coordination: A propylene monomer coordinates to the active titanium center, forming a weak bond with the metal.3. Monomer insertion: The coordinated propylene monomer inserts itself into the metal-carbon bond, forming a new metal-carbon bond and elongating the polymer chain by one monomer unit.4. Chain propagation: Steps 2 and 3 are repeated multiple times, with each new propylene monomer inserting itself into the growing polymer chain. This process continues until the polymer chain reaches the desired length.5. Chain termination: The polymer chain is terminated by reacting with a terminating agent, such as hydrogen or another organoaluminum compound. This step removes the active titanium center from the polymer chain, effectively ending the polymerization process.6. Catalyst removal and polymer recovery: The polymer is separated from the catalyst and any unreacted monomers, typically through a series of washing and filtration steps. The purified polypropylene is then dried and processed into its final form.The synthesis of polypropylene differs from the synthesis of other polymers in several ways:1. Monomer structure: Propylene is a relatively simple monomer with a single double bond, whereas other polymers may be derived from more complex monomers with multiple reactive sites or functional groups.2. Polymerization mechanism: Ziegler-Natta polymerization is a coordination-insertion mechanism that is specific to certain types of monomers, such as olefins like propylene. Other polymers may be synthesized through different mechanisms, such as free-radical, anionic, or cationic polymerizations.3. Catalyst system: The Ziegler-Natta catalyst system is unique to the synthesis of polyolefins like polypropylene and polyethylene. Other types of polymers may require different catalysts or initiators to promote polymerization.4. Stereochemistry: Ziegler-Natta polymerization can produce polymers with a specific stereochemistry, such as isotactic or syndiotactic polypropylene, depending on the choice of catalyst and reaction conditions. Other polymerization methods may not have the same level of stereochemical control.