Rank the following compounds according to their boiling point. The flavor and odor of fruits comes primarily from the esters they contain. For example, a major component in the flavor of oranges is octyl acetate. Draw the organic products formed when octyl acetate reacts with aqueous sodium hydroxide.
The Correct Answer and Explanation is:
To answer your question, we’ll first address the boiling point ranking and then analyze the hydrolysis reaction of octyl acetate with aqueous sodium hydroxide.
Boiling Point Ranking
The boiling point of a compound is influenced by:
- Molecular weight
- Type of intermolecular forces (hydrogen bonding, dipole-dipole, van der Waals)
- Molecular shape and branching
Let’s consider common esters and their boiling points for ranking:
- Octyl acetate (C10H20O2)
- Ethyl acetate (C4H8O2)
- Methyl acetate (C3H6O2)
Ranking from lowest to highest boiling point:
Methyl acetate < Ethyl acetate < Octyl acetate
Explanation:
- Methyl acetate has the lowest boiling point due to its small size and weak van der Waals forces.
- Ethyl acetate is slightly larger, with slightly stronger van der Waals interactions.
- Octyl acetate has a long hydrocarbon chain, significantly increasing its molecular weight and surface area, thus increasing van der Waals interactions and boiling point.
Base Hydrolysis of Octyl Acetate (Saponification Reaction)
Reactants:
Octyl acetate (an ester) + Aqueous NaOH (a strong base)
Products:
- Sodium octanoate (the salt of octanoic acid)
- Ethanol (the alcohol derived from the acetate group)
Reaction:
CH3COO(CH2)7CH3 + NaOH → CH3COONa + CH3(CH2)7OH
Explanation:
In the basic hydrolysis (saponification) of an ester:
- The hydroxide ion (OH⁻) attacks the carbonyl carbon of the ester.
- This forms a tetrahedral intermediate.
- The intermediate collapses, ejecting the alcohol group (in this case, octanol).
- The carboxylic acid formed is deprotonated by the base, resulting in a carboxylate salt.
Thus, octyl acetate hydrolyzes to produce ethanol and sodium octanoate.
This type of reaction is typical in soap-making and is fundamental in biochemistry for breaking down esters under basic conditions.
