Video Transcript
The following molecule forms
through the addition polymerization process. What is the structure of the
monomers that make this polymer? (A), (B), (C), (D), or (E).
The structure of an addition
polymer always depends on its monomers. For example, we can draw a simple
diagram to describe how the structural properties of an alkene monomer determine the
structural properties of the corresponding polymer.
Here, each color represents one of
the groups attached to a carbon atom in the carbon–carbon double bond in an alkene
monomer. These groups can represent a large
number of substituents, such as hydrogen, halogen, or other alkyl groups. We can see that these groups do not
make new bonds as the monomer forms the polymer in addition polymerizations.
All of the substituent groups
remain bonded to the same carbon throughout the polymerization process, as the
double bond breaks and new bonds are formed between monomers. We can also substitute the
geometric shapes with actual elements or groups of elements to figure out which
monomer makes which polymer.
In this question, we are asked
which monomer reacts to form polytetrafluoroethene, or PTFE. We can deduce that the PTFE polymer
is formed from tetrafluoroethene monomers. This is because, as we discussed,
when forming an addition polymer, only the carbon–carbon double bond is reacting,
meaning all of the fluorine atoms in the PTFE product must come from the same
fluorine atoms bonded to the carbons in the starting material.
With this information, let’s answer
the question. What is the structure of the
monomer that makes the polymer shown above? Since the product has four fluorine
atoms bonded to the carbons of the repeating polymer units, we know that the correct
answer must be answer choice (B).
