How do alkenes react to form polymers in polymerisation?

Question

Jacob Anderson · Accepted Answer

Typically ethylene inserts into a #""^(+)M-R# bond, where the #R# group starts as methyl.......

The typical olefin polymerization reaction starts with a metal dimethyl species, #L_2M(CH_3)_2#, where #(i)# #M# is a metal such as titanium or zirconium, and #(ii)# #L# is some ligand that stabilizes and solubilizes the metal centre. Addition of a Lewis acid abstracts one of the methyl groups to yield a species conceived to be #L_2M^(+)(CH_3)#: #L_2M(CH_3)_2 + "aluminum reagent"rarrL_2M^(+)(CH_3) + "methylated aluminium reagent"# The cationic metal center can bind to ethylene: #L_2M^(+)(CH_3)+H_2"C=C"H_2rarrL_2M^(+)(CH_3)(eta^2-H_2"C=C"H_2)# The methyl group bound to the metal centre can migrate to the #eta^2-"bound"# olefin to give a propyl group. And such insertion generates an open coordination site on the metal centre, to which another ethylene can bind, and this reinserts into the #M-"alkyl"# residue. Long chain alkyl residues, polyethylenes, can be built up this way. Your provided text will provide a much better explanation of this.

Elias Aguila · Answer

undefined Alkenes undergo polymerization, a chemical reaction where monomers join together to form long chains or networks called polymers. This process typically involves the breaking of the double bond in the alkene molecule and the formation of new single bonds with other monomer units. Polymerization can occur through two main mechanisms: addition polymerization and condensation polymerization. In addition polymerization, the double bond in the alkene molecule opens up, and the monomer units add to each other sequentially, resulting in a polymer chain with no other byproducts. In condensation polymerization, the monomer units join together while eliminating small molecules such as water or hydrogen chloride.