Video Transcript
The following figure shows a single
alkene monomer. The geometric shapes represent an
element or a group of elements. This monomer combines with
thousands of other identical monomers during an addition polymerization process and
forms one polymer. What is the structure of this
polymer? (A), (B), (C), (D), or (E).
An alkene is a molecule that
contains at least one carbon–carbon double bond. And it can form a polymer during an
addition polymerization reaction.
Let’s take a look at the
polymerization reaction of the simplest alkene molecule first. This will help us understand the
process and be able to apply it to more complicated alkenes later.
Ethylene is the simplest alkene,
and it contains two carbon atoms and four hydrogen atoms. The 𝜋 bond of the carbon–carbon
double bond breaks as ethene monomers combine during an addition polymerization
process and form a larger polymer. In this reaction equation, the
letter 𝑛 represents an indefinite number of monomers. And the product form from the
combination of many ethene monomers is polyethene.
Next let’s consider the
polymerization of chloroethene to understand how the structure of an addition
polymer depends on the bonding of its monomers.
Here you can see what happens when
two chloroethene monomers start to form a polymer. You’ll notice that as the
chloroethene polymer grows, each subunit closely resembles its chloroethene
monomers. The chloroethene monomers bond end
to end. And you’ll notice that every other
carbon is bonded to two hydrogens and two other carbons. And the remaining carbons are
bonded to two other carbons, one hydrogen, and one chlorine atom.
The relative position of the bond
groups does not change as the chloroethene monomers bond end to end. And the hydrogen and chlorine
groups do not make new bonds as the alkene double bond is the one that breaks. And this makes drawing the general
structure of the polymer relatively straightforward, because we simply need to put
the repeating monomer units surrounded by brackets. And it’s important not to forget to
put the letter 𝑛 at the base of your brackets. This represents the large number of
repeating units.
In this question, we are asked to
represent the groups on doubly bonded carbon atoms of an alkene monomer as geometric
shapes and describe their configuration as the monomers form a polymer. At this point, let’s review what
we’ve discussed. We know that polymers are formed
from repeating monomer units. We know that only the carbon–carbon
double bond is involved in addition polymerization reactions and, finally, that the
other bonds within the monomer do not change orientation. And with this information, we
should be able to answer the question.
The following figure shows a single
alkene monomer. The geometric shapes represent an
element or a group of elements. This monomer combines with
thousands of other identical monomers during an addition polymerization process and
forms one polymer. What is the structure of this
polymer?
We’ve been given a specific
orientation of a red circle and a blue triangle bonded to one carbon and a yellow
square and a green diamond bonded to the other. We know that the orientation of the
substituents, or geometric shapes, will not change. And finally, we will show the
monomer inside a set of brackets with the letter 𝑛 representing that is
polymerized. And so the only answer choice where
all of these requirements are true is answer choice (C).
