Question

Which of the following compounds contains the -COOH (carboxylic) group?

• A. Acetic acid
• B. Ethanol
• C. Diethyl ether
• D. Formaldehyde

Hint:

The carboxyl group ($-\text{COOH}$) is a combination of a carbonyl group ($>\text{C}=\text{O}$) and a hydroxyl group ($-\text{OH}$) attached to the same carbon atom. Its name "carboxyl" is derived from carbonyl and hydroxyl.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Organic compounds are classified into various families based on their specific functional groups.
The carboxylic acid family is characterized by the presence of the carboxyl group, which is written as $-\text{COOH}$.

Step 2: Key Formula or Approach:
Analyze the chemical structure and functional group of each option to find the one that possesses the $-\text{COOH}$ group:
- Carboxylic acids have the suffix "-ic acid" or "-oic acid" and contain $-\text{COOH}$.
- Alcohols contain the hydroxyl group ($-\text{OH}$).
- Ethers contain an oxygen bridge between two alkyl groups ($-\text{O}-$).
- Aldehydes contain the formyl group ($-\text{CHO}$).

Step 3: Detailed Explanation:
Let us look closely at the chemical formulas and functional groups of all the choices:
- Acetic acid: The formula is $\text{CH}_3\text{COOH}$. It explicitly contains the functional group $-\text{COOH}$.
- Ethanol: The formula is $\text{CH}_3\text{CH}_2\text{OH}$. It belongs to the alcohol family and contains the $-\text{OH}$ group.
- Diethyl ether: The formula is $\text{CH}_3\text{CH}_2\text{OCH}_2\text{CH}_3$. It belongs to the ether family and contains the $-\text{O}-$ linkage.
- Formaldehyde: The formula is HCHO. It belongs to the aldehyde family and contains the $-\text{CHO}$ group.
Therefore, only acetic acid contains the $-\text{COOH}$ functional group.

Step 4: Final Answer:
The compound that contains the -COOH group is Acetic acid.