Video Transcript
Fill in the blank. PVC polymer is produced from the
addition polymerization of blank. (A) Tetrafluoroethene, (B)
propylene, (C) ethylene, (D) chloroethene, or (E) polyvinyl chloride.
This question is asking about which
monomer can join together to form a larger chain called a polymer. Monomers are atoms or groups of
atoms that when reacted form a long chain of repeating units. And these long chains of repeating
units are known as polymers.
There are two types of
polymerization reactions. We have an addition polymerization
reaction, where a polymer is formed from monomers without the formation of
by-products. And there are condensation
reactions, where the polymer is formed from monomers with the production of a small
molecule by-product. This question however is asking us
to identify the monomer that is used in an addition polymerization reaction to form
PVC. So we know that there will be no
small-molecule by-products formed in this reaction. This also tells us that the
repeating unit of the polymer will look a lot like the starting material.
Now that we understand how a
general addition reaction proceeds, let’s take a look at a more specific
example. Under the right conditions, ethene
monomers undergo addition polymerization to form polyethene. In this process, the double bond in
the ethene monomers breaks, and new carbon–carbon single bonds are formed, joining
the monomers together. This forms the polymer
polyethene. It’s important to notice that the
hydrogens are all still bonded to the same carbon, and they haven’t changed. This is because in the addition
polymerization reaction of alkenes, only the double bond is reacting.
It is also important to note that
the name of the product polyethene is similar to the monomer, the prefix poly-
meaning that there are many ethene monomers that combined to form it.
Now if we look at the structure of
PVC, or polyvinylchloride, we have replaced one of the hydrogens atoms from
polyethylene with a chlorine atom. As we’ve already discussed, in
addition polymerization reaction, only the double bond of the monomer is
reacting. And so we should be able to deduce
that the monomer of polyvinylchloride has one chlorine atom, three hydrogen atoms,
and a carbon–carbon double bond. This gives us the monomer of
chloroethene, also known as vinyl chloride. And with that, we should be able to
revisit and answer the question.
Fill in the blank. PVC polymer is produced from the
addition polymerization of blank. And the correct answer is (D)
chloroethene.
