Video Transcript
The following figure shows an
incomplete addition reaction equation. What structure should replace the
X-term?
Looking at the answer choices, we
can see that each structure is written in a similar fashion. A structural unit is written in
brackets followed by a subscript 𝑛 that indicates the number of times the unit
repeats. This notation is used to represent
a polymer. A polymer is a chemical that can be
formed from similar chemical units that join together. These similar chemical units are
called monomers. So to answer this question, we need
to determine what polymer is produced from the given monomer.
We are told that this reaction is
an addition reaction. This type of reaction produces
addition polymers. Addition polymers are polymers that
can form from monomers without the formation of byproducts. Addition polymers are formed when
the internal bonds in the monomers change, bonding the monomers together.
Let’s see how this applies to the
monomer given in the question. In the presence of a catalyst,
heat, and pressure the 𝜋 bonds in the monomers can break. Then new carbon–carbon single bonds
can form between the monomers to create the polymer. From this, we can see that the
repeating unit in the polymer consists of two carbon atoms that are each bonded to a
hydrogen atom, a chlorine atom, and a carbon atom in the next repeating unit. This is the unit that should be
written inside of brackets when representing the polymer.
Looking at the answer choices, we
can see that the repeating unit matches that of answer choice (E). Therefore, the structure that
should replace the X-term is the structure shown in answer choice (E).
