Video Transcript
Octane molecules can be broken down
into different types of alkenes during a cracking reaction. Which of the following alkenes
cannot be obtained from octane molecules during a cracking reaction?
A cracking reaction is the process
where larger organic molecules are broken down into smaller molecules. So, cracking reactions are a type
of decomposition reactions. A decomposition reaction is a
process where a substance breaks down to form two or more other substances. Cracking reactions are
decomposition reactions because larger molecules break down into smaller ones. Cracking can occur in saturated or
unsaturated hydrocarbons.
Octane is a saturated hydrocarbon
whose prefix oct- indicates that it contains eight carbons. When octane undergoes cracking, a
carbon-to-carbon single bond is broken. An alkane and an alkene are
produced. The alkane and alkene must each
have fewer than eight carbon atoms. Let’s have a look at the number of
carbon atoms in our answer choices.
Answer choices (A), (B), (C), and
(E) all have fewer than eight carbon atoms. These four alkenes are all possible
products in a cracking reaction of octane. Since this question is asking us to
identify the alkene that cannot be a possible product, we can eliminate answer
choices (A), (B), (C), and (E).
Answer choice (D) is an alkene with
eight carbon atoms. In order to be a product from the
cracking reaction of an octane molecule, the alkene must have fewer than eight
carbon atoms. Therefore, the alkene that cannot
be obtained from octane molecules during a cracking reaction is answer choice
(D).
