Video Transcript
Some students attempted to oxidize
five alcohols. Four of the alcohols were
successfully oxidized. The last one was not. What is the structure of the
alcohol that was not successfully oxidized?
Alcohols are molecules that contain
at least one hydroxy group. We are told in the question that
some students attempt to oxidize each of the five alcohols shown. Over the course of the oxidation of
an alcohol, the hydrogen atom of the hydroxy group and a hydrogen atom bonded to the
same carbon atom as the hydroxy group are removed. To make up for this loss of bonds,
a new carbon–oxygen double bond will be formed. This produces a product that
contains a carbonyl group.
Not all alcohols can undergo
oxidation. In this example, we showed that a
secondary alcohol, an alcohol in which the hydroxy group is bonded to a carbon atom
that has two alkyl substituents, can undergo oxidation to produce a molecule called
a ketone.
Primary alcohols in which the
hydroxy group is bonded to a carbon atom that has one alkyl substituent can also
undergo oxidation. The initial reaction is the same as
that of a secondary alcohol. Two hydrogen atoms are removed. Then, a new carbon–oxygen double
bond is formed, producing an aldehyde. Depending on the reaction
conditions, the initial aldehyde produced can be further oxidized in a series of
complex steps to produce a carboxylic acid.
Tertiary alcohols are molecules in
which the hydroxy group is bonded to a carbon atom that has three alkyl
substituents. In a tertiary alcohol, the carbon
atom bonded to the hydroxy group does not have a hydrogen substituent that can be
lost during oxidation. As such, tertiary alcohols cannot
be oxidized.
Now that we’ve examined the
oxidation of primary, secondary, and tertiary alcohols, let’s take a look at the
answer choices.
Answer choices (A) and (C) are
primary alcohols. These alcohols can undergo
oxidation. As we want to identify the alcohol
that was not successfully oxidized, neither answer choice (A) nor (C) can be the
answer to this question.
The alcohols shown in answer
choices (B) and (E) are secondary alcohols. These alcohols can be oxidized, so
neither can be the answer to this question.
The alcohol shown in answer choice
(D) is a tertiary alcohol, which cannot undergo oxidation.
Therefore, the structure of the
alcohol that was not successfully oxidized is the structure shown in answer choice
(D).
