Answers to Concept Checks
5.1
Phenols like p-ethylphenol have increased acidity due to resonance and the electron-
withdrawing character of the phenol aromatic ring. Because p-ethylphenol is a stronger acid than
ethanol, it will have a lower pKa.
1,6-Hexanediol will have the highest boiling point; a molecule with two hydroxyl moieties can
have more hydrogen bonding. The 1-hexanol boiling point will be next, with 1-pentanol having
the lowest boiling point. 1-Hexanol has a higher boiling point than 1-pentanol because the longer
hydrocarbon chain has increased van der Waals forces.5.2
In the presence of strong oxidizing agents, primary alcohols are completely oxidized to
carboxylic acids. Secondary alcohols can only be oxidized to ketones.
Primary alcohols can only be oxidized to aldehydes using pyridinium chlorochromate (PCC).
Mesylates and tosylates are used to convert an alcohol into a better leaving group. This is
particularly useful for nucleophilic substitution reactions because it increases the stability of the
product. They can also be used as protecting groups because many reagents (especially oxidizing
agents) that would react with an alcohol cannot react with these compounds.
Aldehydes or ketones can be reacted with two equivalents of alcohol or a diol to form an acetal
or ketal. Acetals and ketals are less reactive than aldehydes and ketones (especially to reducing
agents), and can thus protect the functional group from reacting. The acetal or ketal can then be
reverted back to the carbonyl by catalytic acid.
5.3
Quinones are produced by oxidation of phenols.
Hydroxyquinones are produced by the oxidation of quinones, adding a variable number of
additional hydroxyl groups.
Ubiquinone has conjugated rings, which stabilize the molecule when accepting electrons.
Additionally, the long alkyl chain in the molecule allows for lipid solubility, which allows the
molecule to function in the phospholipid bilayer.