Problem 100 - Chemistry and Chemical Reactivity

Question

A An unknown ester has the formula \(\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{O}_{2}\) Hydrolysis gives methanol as one product. Identify the ester, and write an equation for the hydrolysis reaction.

Step-by-Step Solution

Answer

The ester is methyl propanoate.

Step 1: Determine the alcohol portion

Given that methanol is produced during the hydrolysis of the ester, methanol (\( ext{CH}_3 ext{OH} \)) is the alcohol part of the ester.

Step 2: Identify the acid portion

Since methanol is derived from the alcohol in the ester, we need the remaining parts. The initial ester formula is \( ext{C}_4 ext{H}_8 ext{O}_2 \). Subtracting methanol \( ( ext{CH}_3 ext{OH}) \) from this, the remaining part is \( ext{C}_3 ext{H}_6 ext{O}_2 \), which corresponds to propanoic acid.

Step 3: Confirm the ester structure

Combine methanol \(( ext{CH}_3 ext{OH})\) and propanoic acid \(( ext{C}_3 ext{H}_6 ext{O}_2)\) to confirm the ester, which is methyl propanoate \( ( ext{CH}_3 ext{CH}_2 ext{COOCH}_3) \). This complete structure supports the given molecular formula and the production of methanol upon hydrolysis.

Step 4: Write the hydrolysis reaction

The hydrolysis of the ester \(( ext{CH}_3 ext{CH}_2 ext{COOCH}_3)\) splits it into methanol \(( ext{CH}_3 ext{OH})\) and propanoic acid \(( ext{CH}_3 ext{CH}_2 ext{COOH})\). The reaction can be written as:\( ext{CH}_3 ext{CH}_2 ext{COOCH}_3 + ext{H}_2 ext{O} \rightarrow ext{CH}_3 ext{OH} + ext{CH}_3 ext{CH}_2 ext{COOH}\)

Key Concepts

methyl propanoate

Methyl propanoate is an organic compound with a fruity odor, commonly utilized in fragrances and flavorings. It is an ester, which means it is formed from the reaction of an alcohol and an acid. The molecular formula for methyl propanoate is \( \text{C}_4\text{H}_8\text{O}_2 \). This particular ester results from the reaction between methanol and propanoic acid.
Methyl propanoate is characterized by its ester functional group, written as \( -\text{COOCH}_3 \). This group is formed when the hydroxyl group \( -\text{OH} \) from an acid is replaced by the alkoxy group \( \text{OCH}_3 \) from the alcohol.
**Key Points about Methyl Propanoate:**

• Often found in nature as part of fruit aromas.
• Used in perfumes and flavorings because of its pleasant smell.
• It is a liquid under normal temperature and pressure with boiling point around 80°C.

Understanding the structure and use of methyl propanoate provides insight into how esters can be formed and used in various industries.

methanol

Methanol, also known as wood alcohol, is the simplest alcohol with the chemical formula \( \text{CH}_3\text{OH} \). It appears as a light, volatile, colorless liquid with a distinctive alcohol odor. Methanol is produced naturally in small amounts by living organisms but is also manufactured industrially.
**Uses of Methanol:**

• Primarily used as an industrial solvent, antifreeze, and denaturant for ethanol.
• Essential in the production of biodiesel through a process called transesterification.
• It serves as a building block for the production of formaldehyde and acetic acid, key ingredients in numerous chemical manufacturing processes.

Methanol is key in ester hydrolysis reactions, such as the one forming part of the ester hydrolysis of methyl propanoate. It acts as the alcohol component in such reactions. Understanding methanol's role in forming and breaking down esters helps in grasping broader chemical processes.

propanoic acid

Propanoic acid, also called propionic acid, is a carboxylic acid with the structural formula \( \text{CH}_3\text{CH}_2\text{COOH} \). It occurs naturally in milk and cheese and is produced industrially for use in food preservation.
**Characteristics of Propanoic Acid:**

• Has a pungent odor similar to vinegar.
• It is a clear, colorless liquid at room temperature and is miscible with water.
• Used as an antifungal and antibacterial agent in food due to its ability to inhibit mold and bacterial growth.

In ester hydrolysis, propanoic acid is the acid part that combines with an alcohol, like methanol, to form an ester such as methyl propanoate. Understanding the role and functionality of propanoic acid is crucial in the study of esterification and saponification reactions.