Final answer:
The polymer of polypropylene with alternating methyl groups along the chain is syndiotactic polypropylene. This arrangement creates a regular and repeating pattern that is different from isotactic and atactic forms.
Step-by-step explanation:
Polypropylene (PP) is a thermoplastic polymer with different structural forms, including atactic, isotactic, and syndiotactic configurations, which refer to the arrangement of the methyl groups along the polymer chain. For a polymer with methyl groups alternating on either side of the chain, the correct type is syndiotactic polypropylene. In this configuration, each methyl group (CH3) is positioned on alternating sides of the polymer chain when viewed in a specific direction, leading to a regular and repeating pattern of stereochemistry.
Isotactic polypropylene has all methyl groups on the same side of the polymer chain, while atactic polypropylene has methyl groups arranged randomly. Copolypropylene contains copolymerized units of propylene and usually ethylene, which does not specify the arrangement of methyl groups as it pertains to the side chain regularity of propylene units. Therefore, the correct answer to the question is: c) Syndiotactic polypropylene.