Poly(ethene) and poly(propene) are both made by addition polymerisation and both contain only carbon and hydrogen. A student says the two polymers must have...
Question 1 Report
Poly(ethene) and poly(propene) are both made by addition polymerisation and both contain only carbon and hydrogen. A student says the two polymers must have identical repeat units. Why is this statement wrong?
Answer Details
The two polymers come from different alkenes, so their repeat units differ. Poly(ethene) is made from CH2=CH2 and repeats -CH2-CH2-, while poly(propene) is made from CH2=CHCH3 and repeats -CH2-CH(CH3)-, so every repeat unit of poly(propene) carries a methyl side group hanging off the backbone. Containing the same two elements does not make two compounds identical, because structure decides identity.
Neither polymer keeps a double bond, since the C=C is used up in joining the units, and neither is made by condensation, because no small molecule is lost. Poly(ethene) contains no chlorine; that is poly(chloroethene).
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